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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title></title><link rel="stylesheet" href="mega-style.css" type="text/css" /><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /></head><body><div xml:lang="en" class="book" lang="en"><div class="titlepage"><hr /></div>
<div class="article"><div class="titlepage"><hr /></div><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr style="height: 90px"><td align="right"><img src="figures/yocto-project-transp.png" align="right" width="135" /></td></tr></table><div class="section" title="1. The Yocto Project Quick Start"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="fake-title"></a>1. The Yocto Project Quick Start</h2></div></div></div><p>Copyright © 2010-2012 Linux Foundation</p></div><div class="section" title="2. Welcome!"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="welcome"></a>2. Welcome!</h2></div></div></div><p>
Welcome to the Yocto Project!
The Yocto Project is an open-source collaboration project focused on embedded Linux
developers.
Among other things, the Yocto Project uses a build system based on the Poky project
to construct complete Linux images.
The Poky project, in turn, draws from and contributes back to the OpenEmbedded project.
</p><p>
If you don't have a system that runs Linux and you want to give the Yocto Project a test run,
you might consider using the Yocto Project Build Appliance.
The Build Appliance allows you to build and boot a custom embedded Linux image with the Yocto
Project using a non-Linux development system.
See the <a class="ulink" href="http://www.yoctoproject.org/documentation/build-appliance" target="_top">Yocto
Project Build Appliance</a> for more information.
</p><p>
On the other hand, if you know all about open-source development, Linux development environments,
Git source repositories and the like and you just want some quick information that lets you try out
the Yocto Project on your Linux system, skip right to the
"<a class="link" href="#super-user" title="6. Super User">Super User</a>" section at the end of this quick start.
</p><p>
For the rest of you, this short document will give you some basic information about the environment and
let you experience it in its simplest form.
After reading this document, you will have a basic understanding of what the Yocto Project is
and how to use some of its core components.
This document steps you through a simple example showing you how to build a small image
and run it using the Quick EMUlator (QEMU emulator).
</p><p>
For more detailed information on the Yocto Project, you should check out these resources:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Website:</em></span> The <a class="ulink" href="http://www.yoctoproject.org" target="_top">Yocto Project Website</a>
provides the latest builds, breaking news, full development documentation, and a rich Yocto
Project Development Community into which you can tap.
</p></li><li class="listitem"><p><span class="emphasis"><em>FAQs:</em></span> Lists commonly asked Yocto Project questions and answers.
You can find two FAQs: <a class="ulink" href="https://wiki.yoctoproject.org/wiki/FAQ" target="_top">Yocto Project FAQ</a> on
a wiki, and the
<a class="link" href="#faq" target="_top">FAQ</a> chapter in
the Yocto Project Reference Manual.
</p></li><li class="listitem"><p><span class="emphasis"><em>Developer Screencast:</em></span> The
<a class="ulink" href="http://vimeo.com/36450321" target="_top">Getting Started with the Yocto Project - New
Developer Screencast Tutorial</a> provides a 30-minute video for the user
new to the Yocto Project but familiar with Linux build systems.</p></li></ul></div><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Due to production processes, there could be differences between the Yocto Project
documentation bundled in a released tarball and the
Yocto Project Quick Start on
the <a class="ulink" href="http://www.yoctoproject.org" target="_top">Yocto Project</a> website.
For the latest version of this manual, see the manual on the website.
</div></div><div class="section" title="3. Introducing the Yocto Project Development Environment"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="yp-intro"></a>3. Introducing the Yocto Project Development Environment</h2></div></div></div><p>
The Yocto Project through the OpenEmbedded build system provides an open source development
environment targeting the ARM, MIPS, PowerPC and x86 architectures for a variety of
platforms including x86-64 and emulated ones.
You can use components from the Yocto Project to design, develop, build, debug, simulate,
and test the complete software stack using Linux, the X Window System, GNOME Mobile-based
application frameworks, and Qt frameworks.
</p><div class="mediaobject" align="center"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="100%"><tr><td align="center"><img src="figures/yocto-environment.png" align="middle" width="100%" /></td></tr></table><div class="caption"><p>The Yocto Project Development Environment</p></div></div><p>
Here are some highlights for the Yocto Project:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Provides a recent Linux kernel along with a set of system commands and libraries suitable for the embedded environment.</p></li><li class="listitem"><p>Makes available system components such as X11, Matchbox, GTK+, Pimlico, Clutter,
GuPNP and Qt (among others) so you can create a richer user interface experience on
devices that use displays or have a GUI.
For devices that don't have a GUI or display, you simply would not employ these
components.</p></li><li class="listitem"><p>Creates a focused and stable core compatible with the OpenEmbedded
project with which you can easily and reliably build and develop.</p></li><li class="listitem"><p>Fully supports a wide range of hardware and device emulation through the QEMU
Emulator.</p></li></ul></div><p>
The Yocto Project can generate images for many kinds of devices.
However, the standard example machines target QEMU full-system emulation for x86, x86-64, ARM, MIPS,
and PPC-based architectures as well as specific hardware such as the
<span class="trademark">Intel</span>® Desktop Board DH55TC.
Because an image developed with the Yocto Project can boot inside a QEMU emulator, the
development environment works nicely as a test platform for developing embedded software.
</p><p>
Another important Yocto Project feature is the Sato reference User Interface.
This optional GNOME mobile-based UI, which is intended for devices with
restricted screen sizes, sits neatly on top of a device using the
GNOME Mobile Stack and provides a well-defined user experience.
Implemented in its own layer, it makes it clear to developers how they can implement
their own user interface on top of a Linux image created with the Yocto Project.
</p></div><div class="section" title="4. What You Need and How You Get It"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="yp-resources"></a>4. What You Need and How You Get It</h2></div></div></div><p>
You need these things to develop in the Yocto Project environment:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>A host system running a supported Linux distribution (i.e. recent releases of
Fedora, openSUSE, CentOS, and Ubuntu).
If the host system supports multiple cores and threads, you can configure the
Yocto Project build system to decrease the time needed to build images
significantly.
</p></li><li class="listitem"><p>The right packages.</p></li><li class="listitem"><p>A release of the Yocto Project.</p></li></ul></div><div class="section" title="4.1. The Linux Distribution"><div class="titlepage"><div><div><h3 class="title"><a id="the-linux-distro"></a>4.1. The Linux Distribution</h3></div></div></div><p>
The Yocto Project team is continually verifying more and more Linux
distributions with each release.
In general, if you have the current release minus one of the following
distributions you should have no problems.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Ubuntu</p></li><li class="listitem"><p>Fedora</p></li><li class="listitem"><p>openSUSE</p></li><li class="listitem"><p>CentOS</p></li></ul></div><p>
For a list of the distributions under validation and their status, see the
<a class="ulink" href="https://wiki.yoctoproject.org/wiki/Distribution_Support" target="_top">Distribution
Support</a> wiki page.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
For notes about using the Yocto Project on a RHEL 4-based host, see the
<a class="ulink" href="https://wiki.yoctoproject.org/wiki/BuildingOnRHEL4" target="_top">BuildingOnRHEL4</a>
wiki page.
</div><p>
</p><p>
The OpenEmbedded build system should be able to run on any modern distribution with Python 2.6 or 2.7.
Earlier releases of Python are known to not work and the system does not support Python 3 at this time.
This document assumes you are running one of the previously noted distributions on your Linux-based
host systems.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
If you attempt to use a distribution not in the above list, you may or may not have success - you
are venturing into untested territory.
Refer to
<a class="ulink" href="http://www.openembedded.org/index.php?title=OEandYourDistro&amp;action=historysubmit&amp;diff=4309&amp;okdid=4225" target="_top">OE and Your Distro</a> and
<a class="ulink" href="http://www.openembedded.org/index.php?title=Required_software&amp;action=historysubmit&amp;diff=4311&amp;oldid=4251" target="_top">Required Software</a>
for information for other distributions used with the OpenEmbedded project, which might be
a starting point for exploration.
If you go down this path, you should expect problems.
When you do, please go to <a class="ulink" href="http://bugzilla.yoctoproject.org" target="_top">Yocto Project Bugzilla</a>
and submit a bug.
We are interested in hearing about your experience.
</p></div></div><div class="section" title="4.2. The Packages"><div class="titlepage"><div><div><h3 class="title"><a id="packages"></a>4.2. The Packages</h3></div></div></div><p>
Packages and package installation vary depending on your development system.
In general, you need to have root access and then install the required packages.
The next few sections show you how to get set up with the right packages for
Ubuntu, Fedora, openSUSE, and CentOS.
</p><div class="section" title="4.2.1. Ubuntu"><div class="titlepage"><div><div><h4 class="title"><a id="ubuntu"></a>4.2.1. Ubuntu</h4></div></div></div><p>
The packages you need for a supported Ubuntu distribution are shown in the following command:
</p><pre class="literallayout">
$ sudo apt-get install sed wget subversion git-core coreutils \
unzip texi2html texinfo libsdl1.2-dev docbook-utils fop gawk \
python-pysqlite2 diffstat make gcc build-essential xsltproc \
g++ desktop-file-utils chrpath libgl1-mesa-dev libglu1-mesa-dev \
autoconf automake groff libtool xterm libxml-parser-perl dblatex
</pre></div><div class="section" title="4.2.2. Fedora"><div class="titlepage"><div><div><h4 class="title"><a id="fedora"></a>4.2.2. Fedora</h4></div></div></div><p>
The packages you need for a supported Fedora distribution are shown in the following
commands:
</p><pre class="literallayout">
$ sudo yum groupinstall "development tools"
$ sudo yum install python m4 make wget curl ftp tar bzip2 gzip \
unzip perl texinfo texi2html diffstat openjade \
docbook-style-dsssl sed docbook-style-xsl docbook-dtds fop libxslt \
docbook-utils sed bc eglibc-devel ccache pcre pcre-devel quilt \
groff linuxdoc-tools patch cmake \
perl-ExtUtils-MakeMaker tcl-devel gettext chrpath ncurses apr \
SDL-devel mesa-libGL-devel mesa-libGLU-devel gnome-doc-utils \
autoconf automake libtool xterm dblatex
</pre></div><div class="section" title="4.2.3. openSUSE"><div class="titlepage"><div><div><h4 class="title"><a id="opensuse"></a>4.2.3. openSUSE</h4></div></div></div><p>
The packages you need for a supported openSUSE distribution are shown in the following
command:
</p><pre class="literallayout">
$ sudo zypper install python gcc gcc-c++ libtool fop \
subversion git chrpath automake make wget xsltproc \
diffstat texinfo freeglut-devel libSDL-devel dblatex
</pre></div><div class="section" title="4.2.4. CentOS"><div class="titlepage"><div><div><h4 class="title"><a id="centos"></a>4.2.4. CentOS</h4></div></div></div><p>
The packages you need for a supported CentOS distribution are shown in the following
commands:
</p><pre class="literallayout">
$ sudo yum -y groupinstall "development tools"
$ sudo yum -y install tetex gawk sqlite-devel vim-common redhat-lsb xz \
m4 make wget curl ftp tar bzip2 gzip python-devel \
unzip perl texinfo texi2html diffstat openjade zlib-devel \
docbook-style-dsssl sed docbook-style-xsl docbook-dtds \
docbook-utils bc glibc-devel pcre pcre-devel \
groff linuxdoc-tools patch cmake \
tcl-devel gettext ncurses apr \
SDL-devel mesa-libGL-devel mesa-libGLU-devel gnome-doc-utils \
autoconf automake libtool xterm dblatex
</pre><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
Depending on the CentOS version you are using, other requirements and dependencies
might exist.
For details, you should look at the CentOS sections on the
<a class="ulink" href="https://wiki.yoctoproject.org/wiki/Poky/GettingStarted/Dependencies" target="_top">Poky/GettingStarted/Dependencies</a>
wiki page.
</p></div></div></div><div class="section" title="4.3. Yocto Project Release"><div class="titlepage"><div><div><h3 class="title"><a id="releases"></a>4.3. Yocto Project Release</h3></div></div></div><p>
You can download the latest Yocto Project release by going to the
<a class="ulink" href="http://www.yoctoproject.org/download" target="_top">Yocto Project Download page</a>.
Just go to the page and click the "Yocto Downloads" link found in the "Download"
navigation pane to the right to view all available Yocto Project releases.
Then, click the "Yocto Release" link for the release you want from the list to
begin the download.
Nightly and developmental builds are also maintained at
<a class="ulink" href="http://autobuilder.yoctoproject.org/nightly/" target="_top">http://autobuilder.yoctoproject.org/nightly/</a>.
However, for this document a released version of Yocto Project is used.
</p><p>
You can also get the Yocto Project files you need by setting up (cloning in Git terms)
a local copy of the <code class="filename">poky</code> Git repository on your host development
system.
Doing so allows you to contribute back to the Yocto Project project.
For information on how to get set up using this method, see the
"<a class="link" href="#local-yp-release" target="_top">Yocto
Project Release</a>" item in the Yocto Project Development Manual.
</p></div></div><div class="section" title="5. A Quick Test Run"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="test-run"></a>5. A Quick Test Run</h2></div></div></div><p>
Now that you have your system requirements in order, you can give the Yocto Project a try.
This section presents some steps that let you do the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Build an image and run it in the QEMU emulator</p></li><li class="listitem"><p>Use a pre-built image and run it in the QEMU emulator</p></li></ul></div><div class="section" title="5.1. Building an Image"><div class="titlepage"><div><div><h3 class="title"><a id="building-image"></a>5.1. Building an Image</h3></div></div></div><p>
In the development environment you will need to build an image whenever you change hardware
support, add or change system libraries, or add or change services that have dependencies.
</p><div class="mediaobject" align="center"><img src="figures/building-an-image.png" align="middle" /><div class="caption"><p>Building an Image</p></div></div><p>
Use the following commands to build your image.
The OpenEmbedded build process creates an entire Linux distribution, including the toolchain,
from source.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
The build process using Sato currently consumes about 50GB of disk space.
To allow for variations in the build process and for future package expansion, we
recommend having at least 100GB of free disk space.
</p></div><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
By default, the build process searches for source code using a pre-determined order
through a set of locations.
If you encounter problems with the build process finding and downloading source code, see the
"<a class="link" href="#how-does-the-yocto-project-obtain-source-code-and-will-it-work-behind-my-firewall-or-proxy-server" target="_top">How does the OpenEmbedded build system obtain source code and will it work behind my
firewall or proxy server?</a>" in the Yocto Project Reference Manual.
</p></div><p>
</p><pre class="literallayout">
$ wget http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/poky-1.2+snapshot-8.0.tar.bz2
$ tar xjf poky-1.2+snapshot-8.0.tar.bz2
$ source poky-1.2+snapshot-8.0/oe-init-build-env poky-1.2+snapshot-8.0-build
</pre><p>
</p><div class="tip" title="Tip" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Tip</h3><p>
To help conserve disk space during builds, you can add the following statement
to your project's configuration file, which for this example
is <code class="filename">poky-1.2+snapshot-8.0-build/conf/local.conf</code>.
Adding this statement deletes the work directory used for building a package
once the package is built.
</p><pre class="literallayout">
INHERIT += "rm_work"
</pre><p>
</p></div><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>In the previous example, the first command retrieves the Yocto Project
release tarball from the source repositories using the
<code class="filename">wget</code> command.
Alternatively, you can go to the
<a class="ulink" href="http://www.yoctoproject.org/download" target="_top">Yocto Project website's Downloads page</a>
to retrieve the tarball.</p></li><li class="listitem"><p>The second command extracts the files from the tarball and places
them into a directory named <code class="filename">poky-1.2+snapshot-8.0</code> in the current
directory.</p></li><li class="listitem"><p>The third command runs the Yocto Project environment setup script.
Running this script defines OpenEmbedded build environment settings needed to
complete the build.
The script also creates the
<a class="link" href="#build-directory" target="_top">build directory</a>,
which is <code class="filename">poky-1.2+snapshot-8.0-build</code> in this case.
After the script runs, your current working directory is set
to the build directory.
Later, when the build completes, the build directory contains all the files
created during the build.
</p></li></ul></div><p>
Take some time to examine your <code class="filename">local.conf</code> file
in your project's configuration directory.
The defaults in that file should work fine.
However, there are some variables of interest at which you might look.
</p><p>
By default, the target architecture for the build is <code class="filename">qemux86</code>,
which produces an image that can be used in the QEMU emulator and is targeted at an
<span class="trademark">Intel</span>® 32-bit based architecture.
To change this default, edit the value of the <code class="filename">MACHINE</code> variable
in the configuration file before launching the build.
</p><p>
Another couple of variables of interest are the
<a class="link" href="#var-BB_NUMBER_THREADS" target="_top"><code class="filename">BB_NUMBER_THREADS</code></a> and the
<a class="link" href="#var-PARALLEL_MAKE" target="_top"><code class="filename">PARALLEL_MAKE</code></a> variables.
By default, these variables are commented out.
However, if you have a multi-core CPU you might want to uncomment
the lines and set both variables equal to twice the number of your
host's processor cores.
Setting these variables can significantly shorten your build time.
</p><p>
Another consideration before you build is the package manager used when creating
the image.
By default, the OpenEmbedded build system uses the RPM package manager.
You can control this configuration by using the
<code class="filename"><a class="link" href="#var-PACKAGE_CLASSES" target="_top"><code class="filename">PACKAGE_CLASSES</code></a></code> variable.
For additional package manager selection information, see
"<a class="link" href="#ref-classes-package" target="_top">Packaging - <code class="filename">package*.bbclass</code></a>"
in the Yocto Project Reference Manual.
</p><p>
Continue with the following command to build an OS image for the target, which is
<code class="filename">core-image-sato</code> in this example.
For information on the <code class="filename">-k</code> option use the
<code class="filename">bitbake --help</code> command or see the
"<a class="link" href="#usingpoky-components-bitbake" target="_top">BitBake</a>" section in
the Yocto Project Reference Manual.
</p><pre class="literallayout">
$ bitbake -k core-image-sato
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
BitBake requires Python 2.6 or 2.7. For more information on this requirement,
see the
<a class="link" href="#faq" target="_top">FAQ</a> in the Yocto Project Reference
Manual.
</p></div><p>
The final command runs the image:
</p><pre class="literallayout">
$ runqemu qemux86
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
Depending on the number of processors and cores, the amount or RAM, the speed of your
Internet connection and other factors, the build process could take several hours the first
time you run it.
Subsequent builds run much faster since parts of the build are cached.
</p></div><p>
</p></div><div class="section" title="5.2. Using Pre-Built Binaries and QEMU"><div class="titlepage"><div><div><h3 class="title"><a id="using-pre-built"></a>5.2. Using Pre-Built Binaries and QEMU</h3></div></div></div><p>
If hardware, libraries and services are stable, you can get started by using a pre-built binary
of the filesystem image, kernel, and toolchain and run it using the QEMU emulator.
This scenario is useful for developing application software.
</p><div class="mediaobject" align="center"><img src="figures/using-a-pre-built-image.png" align="middle" /><div class="caption"><p>Using a Pre-Built Image</p></div></div><p>
For this scenario, you need to do several things:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Install the appropriate stand-alone toolchain tarball.</p></li><li class="listitem"><p>Download the pre-built image that will boot with QEMU.
You need to be sure to get the QEMU image that matches your target machine’s
architecture (e.g. x86, ARM, etc.).</p></li><li class="listitem"><p>Download the filesystem image for your target machine's architecture.
</p></li><li class="listitem"><p>Set up the environment to emulate the hardware and then start the QEMU emulator.
</p></li></ul></div><div class="section" title="5.2.1. Installing the Toolchain"><div class="titlepage"><div><div><h4 class="title"><a id="installing-the-toolchain"></a>5.2.1. Installing the Toolchain</h4></div></div></div><p>
You can download a tarball with the pre-built toolchain, which includes the
<code class="filename">runqemu</code>
script and support files, from the appropriate directory under
<a class="ulink" href="http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/toolchain/" target="_top">http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/toolchain/</a>.
Toolchains are available for 32-bit and 64-bit development systems from the
<code class="filename">i686</code> and <code class="filename">x86-64</code> directories, respectively.
Each type of development system supports five target architectures.
The names of the tarballs are such that a string representing the host system appears
first in the filename and then is immediately followed by a string representing
the target architecture.
</p><pre class="literallayout">
poky-eglibc-&lt;<span class="emphasis"><em>host_system</em></span>&gt;-&lt;<span class="emphasis"><em>arch</em></span>&gt;-toolchain-gmae-&lt;<span class="emphasis"><em>release</em></span>&gt;.tar.bz2
Where:
&lt;<span class="emphasis"><em>host_system</em></span>&gt; is a string representing your development system:
i686 or x86_64.
&lt;<span class="emphasis"><em>arch</em></span>&gt; is a string representing the target architecture:
i586, x86_64, powerpc, mips, or arm.
&lt;<span class="emphasis"><em>release</em></span>&gt; is the version of Yocto Project.
</pre><p>
For example, the following toolchain tarball is for a 64-bit development
host system and a 32-bit target architecture:
</p><pre class="literallayout">
poky-eglibc-x86_64-i586-toolchain-gmae-1.3.tar.bz2
</pre><p>
The toolchain tarballs are self-contained and must be installed into <code class="filename">/opt/poky</code>.
The following commands show how you install the toolchain tarball given a 64-bit development
host system and a 32-bit target architecture.
The example assumes the toolchain tarball is located in <code class="filename">~/toolchains/</code>.
You must have your working directory set to root before unpacking the tarball:
</p><p>
</p><pre class="literallayout">
$ cd /
$ sudo tar -xvjf ~/toolchains/poky-eglibc-x86_64-i586-toolchain-gmae-1.3.tar.bz2
</pre><p>
</p><p>
For more information on how to install tarballs, see the
"<a class="link" href="#using-an-existing-toolchain-tarball" target="_top">Using a Cross-Toolchain Tarball</a>" and
"<a class="link" href="#using-the-toolchain-from-within-the-build-tree" target="_top">Using BitBake and the Build Directory</a>" sections in the Yocto Project Application Developer's Guide.
</p></div><div class="section" title="5.2.2. Downloading the Pre-Built Linux Kernel"><div class="titlepage"><div><div><h4 class="title"><a id="downloading-the-pre-built-linux-kernel"></a>5.2.2. Downloading the Pre-Built Linux Kernel</h4></div></div></div><p>
You can download the pre-built Linux kernel suitable for running in the QEMU emulator from
<a class="ulink" href="http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/machines/qemu" target="_top">http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/machines/qemu</a>.
Be sure to use the kernel that matches the architecture you want to simulate.
Download areas exist for the five supported machine architectures:
<code class="filename">qemuarm</code>, <code class="filename">qemumips</code>, <code class="filename">qemuppc</code>,
<code class="filename">qemux86</code>, and <code class="filename">qemux86-64</code>.
</p><p>
Most kernel files have one of the following forms:
</p><pre class="literallayout">
*zImage-qemu&lt;<span class="emphasis"><em>arch</em></span>&gt;.bin
vmlinux-qemu&lt;<span class="emphasis"><em>arch</em></span>&gt;.bin
Where:
&lt;<span class="emphasis"><em>arch</em></span>&gt; is a string representing the target architecture:
x86, x86-64, ppc, mips, or arm.
</pre><p>
</p><p>
You can learn more about downloading a Yocto Project kernel in the
"<a class="link" href="#local-kernel-files" target="_top">Yocto Project Kernel</a>"
bulleted item in the Yocto Project Development Manual.
</p></div><div class="section" title="5.2.3. Downloading the Filesystem"><div class="titlepage"><div><div><h4 class="title"><a id="downloading-the-filesystem"></a>5.2.3. Downloading the Filesystem</h4></div></div></div><p>
You can also download the filesystem image suitable for your target architecture from
<a class="ulink" href="http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/machines/qemu" target="_top">http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/machines/qemu</a>.
Again, be sure to use the filesystem that matches the architecture you want
to simulate.
</p><p>
The filesystem image has two tarball forms: <code class="filename">ext3</code> and
<code class="filename">tar</code>.
You must use the <code class="filename">ext3</code> form when booting an image using the
QEMU emulator.
The <code class="filename">tar</code> form can be flattened out in your host development system
and used for build purposes with the Yocto Project.
</p><pre class="literallayout">
core-image-&lt;<span class="emphasis"><em>profile</em></span>&gt;-qemu&lt;<span class="emphasis"><em>arch</em></span>&gt;.ext3
core-image-&lt;<span class="emphasis"><em>profile</em></span>&gt;-qemu&lt;<span class="emphasis"><em>arch</em></span>&gt;.tar.bz2
Where:
&lt;<span class="emphasis"><em>profile</em></span>&gt; is the filesystem image's profile:
lsb, lsb-dev, lsb-sdk, lsb-qt3, minimal, minimal-dev, sato, sato-dev, or sato-sdk.
For information on these types of image profiles, see the
"<a class="link" href="#ref-images" target="_top">Images</a>" chapter
in the Yocto Project Reference Manual.
&lt;<span class="emphasis"><em>arch</em></span>&gt; is a string representing the target architecture:
x86, x86-64, ppc, mips, or arm.
</pre><p>
</p></div><div class="section" title="5.2.4. Setting Up the Environment and Starting the QEMU Emulator"><div class="titlepage"><div><div><h4 class="title"><a id="setting-up-the-environment-and-starting-the-qemu-emulator"></a>5.2.4. Setting Up the Environment and Starting the QEMU Emulator</h4></div></div></div><p>
Before you start the QEMU emulator, you need to set up the emulation environment.
The following command form sets up the emulation environment.
</p><pre class="literallayout">
$ source /opt/poky/1.3/environment-setup-&lt;<span class="emphasis"><em>arch</em></span>&gt;-poky-linux-&lt;<span class="emphasis"><em>if</em></span>&gt;
Where:
&lt;<span class="emphasis"><em>arch</em></span>&gt; is a string representing the target architecture:
i586, x86_64, ppc603e, mips, or armv5te.
&lt;<span class="emphasis"><em>if</em></span>&gt; is a string representing an embedded application binary interface.
Not all setup scripts include this string.
</pre><p>
</p><p>
Finally, this command form invokes the QEMU emulator
</p><pre class="literallayout">
$ runqemu &lt;<span class="emphasis"><em>qemuarch</em></span>&gt; &lt;<span class="emphasis"><em>kernel-image</em></span>&gt; &lt;<span class="emphasis"><em>filesystem-image</em></span>&gt;
Where:
&lt;<span class="emphasis"><em>qemuarch</em></span>&gt; is a string representing the target architecture: qemux86, qemux86-64,
qemuppc, qemumips, or qemuarm.
&lt;<span class="emphasis"><em>kernel-image</em></span>&gt; is the architecture-specific kernel image.
&lt;<span class="emphasis"><em>filesystem-image</em></span>&gt; is the .ext3 filesystem image.
</pre><p>
</p><p>
Continuing with the example, the following two commands setup the emulation
environment and launch QEMU.
This example assumes the root filesystem (<code class="filename">.ext3</code> file) and
the pre-built kernel image file both reside in your home directory.
The kernel and filesystem are for a 32-bit target architecture.
</p><pre class="literallayout">
$ cd $HOME
$ source /opt/poky/1.3/environment-setup-i586-poky-linux
$ runqemu qemux86 bzImage-qemux86.bin \
core-image-sato-qemux86.ext3
</pre><p>
</p><p>
The environment in which QEMU launches varies depending on the filesystem image and on the
target architecture.
For example, if you source the environment for the ARM target
architecture and then boot the minimal QEMU image, the emulator comes up in a new
shell in command-line mode.
However, if you boot the SDK image, QEMU comes up with a GUI.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>Booting the PPC image results in QEMU launching in the same shell in
command-line mode.</div><p>
</p></div></div></div><div class="section" title="6. Super User"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="super-user"></a>6. Super User
</h2></div></div></div><p>
This section
<sup>[<a id="id1482592" href="#ftn.id1482592" class="footnote">1</a>]</sup>
gives you a very fast description of how to use the Yocto Project to build images
for a BeagleBoard xM starting from scratch.
The steps were performed on a 64-bit Ubuntu 10.04 system.
</p><div class="section" title="6.1. Getting the Yocto Project"><div class="titlepage"><div><div><h3 class="title"><a id="getting-yocto"></a>6.1. Getting the Yocto Project</h3></div></div></div><p>
Set up your <a class="link" href="#source-directory" target="_top">source directory</a>
one of two ways:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Tarball:</em></span>
Use if you want the latest stable release:
</p><pre class="literallayout">
$ wget http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/poky-1.2+snapshot-8.0.tar.bz2
$ tar xvjf poky-1.2+snapshot-8.0.tar.bz2
</pre></li><li class="listitem"><p><span class="emphasis"><em>Git Repository:</em></span>
Use if you want to work with cutting edge development content:
</p><pre class="literallayout">
$ git clone git://git.yoctoproject.org/poky
</pre></li></ul></div><p>
The remainder of the section assumes the Git repository method.
</p></div><div class="section" title="6.2. Setting Up Your Host"><div class="titlepage"><div><div><h3 class="title"><a id="setting-up-your-host"></a>6.2. Setting Up Your Host</h3></div></div></div><p>
You need some packages for everything to work.
Rather than duplicate them here, look at the "<a class="link" href="#packages" title="4.2. The Packages">The Packages</a>"
section earlier in this quick start.
</p></div><div class="section" title="6.3. Initializing the Build Environment"><div class="titlepage"><div><div><h3 class="title"><a id="initializing-the-build-environment"></a>6.3. Initializing the Build Environment</h3></div></div></div><p>
From the parent directory of local source directory, initialize your environment
and provide a meaningful
<a class="link" href="#build-directory" target="_top">build directory</a>
name:
</p><pre class="literallayout">
$ source poky/oe-init-build-env mybuilds
</pre><p>
At this point, the <code class="filename">mybuilds</code> directory has been created for you
and it is now your current working directory.
If you don't provide your own directory name it defaults to <code class="filename">build</code>.
</p></div><div class="section" title="6.4. Configuring the local.conf File"><div class="titlepage"><div><div><h3 class="title"><a id="configuring-the-local.conf-file"></a>6.4. Configuring the local.conf File</h3></div></div></div><p>
Initializing the build environment creates a <code class="filename">conf/local.conf</code> configuration file
in the build directory.
You need to manually edit this file to specify the machine you are building and to optimize
your build time.
Here are the minimal changes to make:
</p><pre class="literallayout">
BB_NUMBER_THREADS = "8"
PARALLEL_MAKE = "-j 8"
MACHINE ?= "beagleboard"
</pre><p>
Briefly, set <a class="link" href="#var-BB_NUMBER_THREADS" target="_top"><code class="filename">BB_NUMBER_THREADS</code></a>
and <a class="link" href="#var-PARALLEL_MAKE" target="_top"><code class="filename">PARALLEL_MAKE</code></a> to
twice your host processor's number of cores.
</p><p>
A good deal that goes into a Yocto Project build is simply downloading all of the source
tarballs.
Maybe you have been working with another build system (OpenEmbedded, Angstrom, etc) for which
you've built up a sizable directory of source tarballs.
Or perhaps someone else has such a directory for which you have read access.
If so, you can save time by adding the <code class="filename">PREMIRRORS</code>
statement to your configuration file so that local directories are first checked for existing
tarballs before running out to the net:
</p><pre class="literallayout">
PREMIRRORS_prepend = "\
git://.*/.* file:///home/you/dl/ \n \
svn://.*/.* file:///home/you/dl/ \n \
cvs://.*/.* file:///home/you/dl/ \n \
ftp://.*/.* file:///home/you/dl/ \n \
http://.*/.* file:///home/you/dl/ \n \
https://.*/.* file:///home/you/dl/ \n"
</pre><p>
</p></div><div class="section" title="6.5. Building the Image"><div class="titlepage"><div><div><h3 class="title"><a id="building-the-image"></a>6.5. Building the Image</h3></div></div></div><p>
At this point, you need to select an image to build for the BeagleBoard xM.
If this is your first build using the Yocto Project, you should try the smallest and simplest
image:
</p><pre class="literallayout">
$ bitbake core-image-minimal
</pre><p>
Now you just wait for the build to finish.
</p><p>
Here are some variations on the build process that could be helpful:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Fetch all the necessary sources without starting the build:
</p><pre class="literallayout">
$ bitbake -c fetchall core-image-minimal
</pre><p>
This variation guarantees that you have all the sources for that BitBake target
should you to disconnect from the net and want to do the build later offline.
</p></li><li class="listitem"><p>Specify to continue the build even if BitBake encounters an error.
By default, BitBake aborts the build when it encounters an error.
This command keeps a faulty build going:
</p><pre class="literallayout">
$ bitbake -k core-image-minimal
</pre></li></ul></div><p>
</p><p>
Once you have your image, you can take steps to load and boot it on the target hardware.
</p></div></div><div class="footnotes"><br /><hr width="100" align="left" /><div class="footnote"><p><sup>[<a id="ftn.id1482592" href="#id1482592" class="para">1</a>] </sup>
Kudos and thanks to Robert P. J. Day of
<a class="ulink" href="http://www.crashcourse.ca" target="_top">CrashCourse</a> for providing the basis
for this "expert" section with information from one of his
<a class="ulink" href="http://www.crashcourse.ca/wiki/index.php/Yocto_Project_Quick_Start" target="_top">wiki</a>
pages.
</p></div></div></div>
<table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="100%"><tr><td align="left"><img src="figures/dev-title.png" align="left" width="100%" /></td></tr></table>
<div xml:lang="en" class="book" lang="en"><div class="titlepage"><div><div><h1 class="title"><a id="dev-manual"></a></h1></div><div><div class="authorgroup">
<div class="author"><h3 class="author"><span class="firstname">Scott</span> <span class="surname">Rifenbark</span></h3><div class="affiliation">
<span class="orgname">Intel Corporation<br /></span>
</div><code class="email">&lt;<a class="email" href="mailto:scott.m.rifenbark@intel.com">scott.m.rifenbark@intel.com</a>&gt;</code></div>
</div></div><div><p class="copyright">Copyright © 2010-2012 Linux Foundation</p></div><div><div class="legalnotice" title="Legal Notice"><a id="id1482939"></a>
<p>
Permission is granted to copy, distribute and/or modify this document under
the terms of the <a class="ulink" href="http://creativecommons.org/licenses/by-sa/2.0/uk/" target="_top">
Creative Commons Attribution-Share Alike 2.0 UK: England &amp; Wales</a> as published by
Creative Commons.
</p>
<div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Due to production processes, there could be differences between the Yocto Project
documentation bundled in the release tarball and the
Yocto Project Development Manual on
the <a class="ulink" href="http://www.yoctoproject.org" target="_top">Yocto Project</a> website.
For the latest version of this manual, see the manual on the website.
</div>
</div></div><div><div class="revhistory"><table border="1" width="100%" summary="Revision history"><tr><th align="left" valign="top" colspan="2"><b>Revision History</b></th></tr>
<tr><td align="left">Revision 1.1</td><td align="left">6 October 2011</td></tr><tr><td align="left" colspan="2">The initial document released with the Yocto Project 1.1 Release.</td></tr>
<tr><td align="left">Revision 1.2</td><td align="left">April 2012</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.2 Release.</td></tr>
<tr><td align="left">Revision 1.3</td><td align="left">Sometime in 2012</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.3 Release.</td></tr>
</table></div></div></div><hr /></div>
<div class="chapter" title="Chapter 1. The Yocto Project Development Manual"><div class="titlepage"><div><div><h2 class="title"><a id="dev-manual-intro"></a>Chapter 1. The Yocto Project Development Manual</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#intro">1.1. Introduction</a></span></dt><dt><span class="section"><a href="#what-this-manual-provides">1.2. What this Manual Provides</a></span></dt><dt><span class="section"><a href="#what-this-manual-does-not-provide">1.3. What this Manual Does Not Provide</a></span></dt><dt><span class="section"><a href="#other-information">1.4. Other Information</a></span></dt></dl></div><div class="section" title="1.1. Introduction"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="intro"></a>1.1. Introduction</h2></div></div></div><p>
Welcome to the Yocto Project Development Manual!
This manual gives you an idea of how to use the Yocto Project to develop embedded Linux
images and user-space applications to run on targeted devices.
Reading this manual gives you an overview of image, kernel, and user-space application development
using the Yocto Project.
Because much of the information in this manual is general, it contains many references to other
sources where you can find more detail.
For example, detailed information on Git, repositories and open source in general
can be found in many places.
Another example is how to get set up to use the Yocto Project, which our Yocto Project
Quick Start covers.
</p><p>
The Yocto Project Development Manual, however, does provide detailed examples on how to create a
Board Support Package (BSP), change the kernel source code, and reconfigure the kernel.
You can find this information in the appendices of the manual.
</p></div><div class="section" title="1.2. What this Manual Provides"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="what-this-manual-provides"></a>1.2. What this Manual Provides</h2></div></div></div><p>
The following list describes what you can get from this guide:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Information that lets you get set
up to develop using the Yocto Project.</p></li><li class="listitem"><p>Information to help developers who are new to the open source environment
and to the distributed revision control system Git, which the Yocto Project
uses.</p></li><li class="listitem"><p>An understanding of common end-to-end development models and tasks.</p></li><li class="listitem"><p>Development case overviews for both system development and user-space
applications.</p></li><li class="listitem"><p>An overview and understanding of the emulation environment used with
the Yocto Project (QEMU).</p></li><li class="listitem"><p>An understanding of basic kernel architecture and concepts.</p></li><li class="listitem"><p>Many references to other sources of related information.</p></li></ul></div><p>
</p></div><div class="section" title="1.3. What this Manual Does Not Provide"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="what-this-manual-does-not-provide"></a>1.3. What this Manual Does Not Provide</h2></div></div></div><p>
This manual will not give you the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Step-by-step instructions if those instructions exist in other Yocto
Project documentation.
For example, the Yocto Project Development Manual contains detailed
instruction on how to obtain and configure the
<span class="trademark">Eclipse</span>™ Yocto Plug-in.</p></li><li class="listitem"><p>Reference material.
This type of material resides in an appropriate reference manual.
For example, system variables are documented in the
Yocto Project Reference Manual.</p></li><li class="listitem"><p>Detailed public information that is not specific to the Yocto Project.
For example, exhaustive information on how to use Git is covered better through the
Internet than in this manual.</p></li></ul></div><p>
</p></div><div class="section" title="1.4. Other Information"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="other-information"></a>1.4. Other Information</h2></div></div></div><p>
Because this manual presents overview information for many different topics, you will
need to supplement it with other information.
The following list presents other sources of information you might find helpful:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>The <a class="ulink" href="http://www.yoctoproject.org" target="_top">Yocto Project Website</a>:
</em></span> The home page for the Yocto Project provides lots of information on the project
as well as links to software and documentation.</p></li><li class="listitem"><p><span class="emphasis"><em>
Yocto Project Quick Start:</em></span> This short document lets you get started
with the Yocto Project quickly and start building an image.</p></li><li class="listitem"><p><span class="emphasis"><em>
Yocto Project Reference Manual:</em></span> This manual is a reference
guide to the OpenEmbedded build system known as "Poky."
The manual also contains a reference chapter on Board Support Package (BSP)
layout.</p></li><li class="listitem"><p><span class="emphasis"><em>
Yocto Project Application Developer's Guide:</em></span>
This guide provides information that lets you get going with the Application
Development Toolkit (ADT) and stand-alone cross-development toolchains to
develop projects using the Yocto Project.</p></li><li class="listitem"><p><span class="emphasis"><em>
Yocto Project Board Support Package (BSP) Developer's Guide:</em></span>
This guide defines the structure for BSP components.
Having a commonly understood structure encourages standardization.</p></li><li class="listitem"><p><span class="emphasis"><em>
Yocto Project Kernel Architecture and Use Manual:</em></span>
This manual describes the architecture of the Yocto Project kernel and provides
some work flow examples.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="ulink" href="http://www.youtube.com/watch?v=3ZlOu-gLsh0" target="_top">
Eclipse IDE Yocto Plug-in</a>:</em></span> A step-by-step instructional video that
demonstrates how an application developer uses Yocto Plug-in features within
the Eclipse IDE.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="ulink" href="https://wiki.yoctoproject.org/wiki/FAQ" target="_top">FAQ</a>:</em></span>
A list of commonly asked questions and their answers.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="ulink" href="http://www.yoctoproject.org/download/yocto/yocto-project-1.1-release-notes-poky-8.0" target="_top">
Release Notes</a>:</em></span> Features, updates and known issues for the current
release of the Yocto Project.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="ulink" href="http://www.yoctoproject.org/projects/hob" target="_top">
Hob</a>:</em></span> A graphical user interface for BitBake.
Hob's primary goal is to enable a user to perform common tasks more easily.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="ulink" href="http://www.yoctoproject.org/documentation/build-appliance" target="_top">
Build Appliance</a>:</em></span> A bootable custom embedded Linux image you can
either build using a non-Linux development system (VMware applications) or download
from the Yocto Project website.
See the <a class="ulink" href="http://www.yoctoproject.org/documentation/build-appliance" target="_top">Build Appliance</a>
page for more information.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="ulink" href="http://bugzilla.yoctoproject.org" target="_top">Bugzilla</a>:</em></span>
The bug tracking application the Yocto Project uses.
If you find problems with the Yocto Project, you should report them using this
application.</p></li><li class="listitem"><p><span class="emphasis"><em>
Yocto Project Mailing Lists:</em></span> To subscribe to the Yocto Project mailing
lists, click on the following URLs and follow the instructions:
</p><div class="itemizedlist"><ul class="itemizedlist" type="circle"><li class="listitem"><p><a class="ulink" href="http://lists.yoctoproject.org/listinfo/yocto" target="_top">http://lists.yoctoproject.org/listinfo/yocto</a> for a
Yocto Project Discussions mailing list.</p></li><li class="listitem"><p><a class="ulink" href="http://lists.yoctoproject.org/listinfo/poky" target="_top">http://lists.yoctoproject.org/listinfo/poky</a> for a
Yocto Project Discussions mailing list about the Poky build system.</p></li><li class="listitem"><p><a class="ulink" href="http://lists.yoctoproject.org/listinfo/yocto-announce" target="_top">http://lists.yoctoproject.org/listinfo/yocto-announce</a>
for a mailing list to receive official Yocto Project announcements for developments and
as well as Yocto Project milestones.</p></li></ul></div></li><li class="listitem"><p><span class="emphasis"><em>Internet Relay Chat (IRC):</em></span>
Two IRC channels on freenode are available
for Yocto Project and Poky discussions: <code class="filename">#yocto</code> and
<code class="filename">#poky</code>, respectively.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="ulink" href="http://o-hand.com" target="_top">OpenedHand</a>:</em></span>
The company that initially developed the Poky project, which is the basis
for the OpenEmbedded build system used by the Yocto Project.
OpenedHand was acquired by Intel Corporation in 2008.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="ulink" href="http://www.intel.com/" target="_top">Intel Corporation</a>:</em></span>
A multinational semiconductor chip manufacturer company whose Software and
Services Group created and supports the Yocto Project.
Intel acquired OpenedHand in 2008.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="ulink" href="http://www.openembedded.org" target="_top">OpenEmbedded</a>:</em></span>
The build system used by the Yocto Project.
This project is the upstream, generic, embedded distribution from which the Yocto
Project derives its build system (Poky) from and to which it contributes.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="ulink" href="http://developer.berlios.de/projects/bitbake/" target="_top">
BitBake</a>:</em></span> The tool used by the OpenEmbedded build system
to process project metadata.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="ulink" href="http://docs.openembedded.org/bitbake/html/" target="_top">
BitBake User Manual</a>:</em></span> A comprehensive guide to the BitBake tool.
</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="ulink" href="http://wiki.qemu.org/Index.html" target="_top">QEMU</a>:
</em></span> An open-source machine emulator and virtualizer.</p></li></ul></div><p>
</p></div></div>
<div class="chapter" title="Chapter 2. Getting Started with the Yocto Project"><div class="titlepage"><div><div><h2 class="title"><a id="dev-manual-start"></a>Chapter 2. Getting Started with the Yocto Project</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#introducing-the-yocto-project">2.1. Introducing the Yocto Project</a></span></dt><dt><span class="section"><a href="#getting-setup">2.2. Getting Set Up</a></span></dt><dt><span class="section"><a href="#building-images">2.3. Building Images</a></span></dt><dt><span class="section"><a href="#using-pre-built-binaries-and-qemu">2.4. Using Pre-Built Binaries and QEMU</a></span></dt></dl></div><p>
This chapter introduces the Yocto Project and gives you an idea of what you need to get started.
You can find enough information to set up your development host and build or use images for
hardware supported by the Yocto Project by reading the
Yocto Project Quick Start.
</p><p>
The remainder of this chapter summarizes what is in the Yocto Project Quick Start and provides
some higher-level concepts you might want to consider.
</p><div class="section" title="2.1. Introducing the Yocto Project"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="introducing-the-yocto-project"></a>2.1. Introducing the Yocto Project</h2></div></div></div><p>
The Yocto Project is an open-source collaboration project focused on embedded Linux development.
The project currently provides a build system, which is
referred to as the OpenEmbedded build system in the Yocto Project documentation.
The Yocto Project provides various ancillary tools suitable for the embedded developer
and also features the Sato reference User Interface, which is optimized for
stylus driven, low-resolution screens.
</p><p>
You can use the OpenEmbedded build system, which uses
<a class="ulink" href="http://docs.openembedded.org/bitbake/html/" target="_top">BitBake</a>, to develop complete Linux
images and associated user-space applications for architectures based on ARM, MIPS, PowerPC,
x86 and x86-64.
While the Yocto Project does not provide a strict testing framework,
it does provide or generate for you artifacts that let you perform target-level and
emulated testing and debugging.
Additionally, if you are an <span class="trademark">Eclipse</span>™
IDE user, you can install an Eclipse Yocto Plug-in to allow you to
develop within that familiar environment.
</p></div><div class="section" title="2.2. Getting Set Up"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="getting-setup"></a>2.2. Getting Set Up</h2></div></div></div><p>
Here is what you need to get set up to use the Yocto Project:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Host System:</em></span> You should have a reasonably current
Linux-based host system.
You will have the best results with a recent release of Fedora,
OpenSUSE, Ubuntu, or CentOS as these releases are frequently tested against the Yocto Project
and officially supported.
You should also have about 100 gigabytes of free disk space for building images.
</p></li><li class="listitem"><p><span class="emphasis"><em>Packages:</em></span> The OpenEmbedded build system
requires certain packages exist on your development system (e.g. Python 2.6 or 2.7).
See "<a class="link" href="#packages" target="_top">The Packages</a>"
section in the Yocto Project Quick Start for the exact package
requirements and the installation commands to install them
for the supported distributions.</p></li><li class="listitem"><p><a id="local-yp-release"></a><span class="emphasis"><em>Yocto Project Release:</em></span>
You need a release of the Yocto Project.
You set up a with local <a class="link" href="#source-directory">source directory</a>
one of two ways depending on whether you
are going to contribute back into the Yocto Project or not.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Regardless of the method you use, this manual refers to the resulting local
hierarchical set of files as the "source directory."
</div><p>
</p><div class="itemizedlist"><ul class="itemizedlist" type="circle"><li class="listitem"><p><span class="emphasis"><em>Tarball Extraction:</em></span> If you are not going to contribute
back into the Yocto Project, you can simply download a Yocto Project release you want
from the website’s <a class="ulink" href="http://www.yoctoproject.org/download" target="_top">download page</a>.
Once you have the tarball, just extract it into a directory of your choice.</p><p>For example, the following command extracts the Yocto Project 1.3
release tarball
into the current working directory and sets up the local source directory
with a top-level folder named <code class="filename">poky-1.2+snapshot-8.0</code>:
</p><pre class="literallayout">
$ tar xfj poky-1.2+snapshot-8.0.tar.bz2
</pre><p>This method does not produce a local Git repository.
Instead, you simply end up with a snapshot of the release.</p></li><li class="listitem"><p><span class="emphasis"><em>Git Repository Method:</em></span> If you are going to be contributing
back into the Yocto Project or you simply want to keep up
with the latest developments, you should use Git commands to set up a local
Git repository of the upstream <code class="filename">poky</code> source repository.
Doing so creates a repository with a complete history of changes and allows
you to easily submit your changes upstream to the project.
Because you cloned the repository, you have access to all the Yocto Project development
branches and tag names used in the upstream repository.</p><p>The following transcript shows how to clone the <code class="filename">poky</code>
Git repository into the current working directory.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>You can view the Yocto Project Source Repositories at
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi" target="_top">http://git.yoctoproject.org/cgit.cgi</a></div><p>
The command creates the local repository in a directory named <code class="filename">poky</code>.
For information on Git used within the Yocto Project, see the
"<a class="link" href="#git" title="3.6. Git">Git</a>" section.
</p><pre class="literallayout">
$ git clone git://git.yoctoproject.org/poky
Initialized empty Git repository in /home/scottrif/poky/.git/
remote: Counting objects: 141863, done.
remote: Compressing objects: 100% (38624/38624), done.
remote: Total 141863 (delta 99661), reused 141816 (delta 99614)
Receiving objects: 100% (141863/141863), 76.64 MiB | 126 KiB/s, done.
Resolving deltas: 100% (99661/99661), done.
</pre><p>For another example of how to set up your own local Git repositories, see this
<a class="ulink" href="https://wiki.yoctoproject.org/wiki/Transcript:_from_git_checkout_to_meta-intel_BSP" target="_top">
wiki page</a>, which describes how to create both <code class="filename">poky</code>
and <code class="filename">meta-intel</code> Git repositories.</p></li></ul></div></li><li class="listitem"><p><a id="local-kernel-files"></a><span class="emphasis"><em>Yocto Project Kernel:</em></span>
If you are going to be making modifications to a supported Yocto Project kernel, you
need to establish local copies of the source.
You can find Git repositories of supported Yocto Project Kernels organized under
"Yocto Project Linux Kernel" in the Yocto Project Source Repositories at
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi" target="_top">http://git.yoctoproject.org/cgit.cgi</a>.</p><p>This setup involves creating a bare clone of the Yocto Project kernel and then
copying that cloned repository.
You can create the bare clone and the copy of the bare clone anywhere you like.
For simplicity, it is recommended that you create these structures outside of the
source directory (usually <code class="filename">poky</code>).</p><p>As an example, the following transcript shows how to create the bare clone
of the <code class="filename">linux-yocto-3.2</code> kernel and then create a copy of
that clone.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>When you have a local Yocto Project kernel Git repository, you can
reference that repository rather than the upstream Git repository as
part of the <code class="filename">clone</code> command.
Doing so can speed up the process.</div><p>In the following example, the bare clone is named
<code class="filename">linux-yocto-3.2.git</code>, while the
copy is named <code class="filename">my-linux-yocto-3.2-work</code>:
</p><pre class="literallayout">
$ git clone --bare git://git.yoctoproject.org/linux-yocto-3.2 linux-yocto-3.2.git
Initialized empty Git repository in /home/scottrif/linux-yocto-3.2.git/
remote: Counting objects: 2468027, done.
remote: Compressing objects: 100% (392255/392255), done.
remote: Total 2468027 (delta 2071693), reused 2448773 (delta 2052498)
Receiving objects: 100% (2468027/2468027), 530.46 MiB | 129 KiB/s, done.
Resolving deltas: 100% (2071693/2071693), done.
</pre><p>Now create a clone of the bare clone just created:
</p><pre class="literallayout">
$ git clone linux-yocto-3.2.git my-linux-yocto-3.2-work
Initialized empty Git repository in /home/scottrif/my-linux-yocto-3.2-work/.git/
Checking out files: 100% (37619/37619), done.
</pre></li><li class="listitem"><p><a id="poky-extras-repo"></a><span class="emphasis"><em>
The <code class="filename">poky-extras</code> Git Repository</em></span>:
The <code class="filename">poky-extras</code> Git repository contains metadata needed
only if you are modifying and building the kernel image.
In particular, it contains the kernel BitBake append (<code class="filename">.bbappend</code>)
files that you
edit to point to your locally modified kernel source files and to build the kernel
image.
Pointing to these local files is much more efficient than requiring a download of the
kernel's source files from upstream each time you make changes to the kernel.</p><p>You can find the <code class="filename">poky-extras</code> Git Repository in the
"Yocto Metadata Layers" area of the Yocto Project Source Repositories at
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi" target="_top">http://git.yoctoproject.org/cgit.cgi</a>.
It is good practice to create this Git repository inside the source directory.</p><p>Following is an example that creates the <code class="filename">poky-extras</code> Git
repository inside the source directory, which is named <code class="filename">poky</code>
in this case:
</p><pre class="literallayout">
$ git clone git://git.yoctoproject.org/poky-extras poky-extras
Initialized empty Git repository in /home/scottrif/poky/poky-extras/.git/
remote: Counting objects: 618, done.
remote: Compressing objects: 100% (558/558), done.
remote: Total 618 (delta 192), reused 307 (delta 39)
Receiving objects: 100% (618/618), 526.26 KiB | 111 KiB/s, done.
Resolving deltas: 100% (192/192), done.
</pre></li><li class="listitem"><p><a id="supported-board-support-packages-(bsps)"></a><span class="emphasis"><em>Supported Board
Support Packages (BSPs):</em></span>
The Yocto Project provides a layer called <code class="filename">meta-intel</code> and
it is maintained in its own separate Git repository.
The <code class="filename">meta-intel</code> layer contains many supported
<a class="link" href="#bsp-layers" target="_top">BSP Layers</a>.</p><p>Similar considerations exist for setting up the <code class="filename">meta-intel</code>
layer.
You can get set up for BSP development one of two ways: tarball extraction or
with a local Git repository.
It is a good idea to use the same method that you used to set up the source directory.
Regardless of the method you use, the Yocto Project uses the following BSP layer
naming scheme:
</p><pre class="literallayout">
meta-&lt;BSP_name&gt;
</pre><p>
where &lt;BSP_name&gt; is the recognized BSP name.
Here are some examples:
</p><pre class="literallayout">
meta-crownbay
meta-emenlow
meta-n450
</pre><p>
See the
"<a class="link" href="#bsp-layers" target="_top">BSP Layers</a>"
section in the Yocto Project Board Support Package (BSP) Developer's Guide for more
information on BSP Layers.
</p><div class="itemizedlist"><ul class="itemizedlist" type="circle"><li class="listitem"><p><span class="emphasis"><em>Tarball Extraction:</em></span> You can download any released
BSP tarball from the same
<a class="ulink" href="http://www.yoctoproject.org/download" target="_top">download site</a> used
to get the Yocto Project release.
Once you have the tarball, just extract it into a directory of your choice.
Again, this method just produces a snapshot of the BSP layer in the form
of a hierarchical directory structure.</p></li><li class="listitem"><p><span class="emphasis"><em>Git Repository Method:</em></span> If you are working
with a local Git repository for your source directory, you should also use this method
to set up the <code class="filename">meta-intel</code> Git repository.
You can locate the <code class="filename">meta-intel</code> Git repository in the
"Yocto Metadata Layers" area of the Yocto Project Source Repositories at
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi" target="_top">http://git.yoctoproject.org/cgit.cgi</a>.</p><p>Typically, you set up the <code class="filename">meta-intel</code> Git repository inside
the source directory.
For example, the following transcript shows the steps to clone the
<code class="filename">meta-intel</code>
Git repository inside the local <code class="filename">poky</code> Git repository.
</p><pre class="literallayout">
$ git clone git://git.yoctoproject.org/meta-intel.git
Initialized empty Git repository in /home/scottrif/poky/meta-intel/.git/
remote: Counting objects: 3380, done.
remote: Compressing objects: 100% (2750/2750), done.
remote: Total 3380 (delta 1689), reused 227 (delta 113)
Receiving objects: 100% (3380/3380), 1.77 MiB | 128 KiB/s, done.
Resolving deltas: 100% (1689/1689), done.
</pre><p>The same
<a class="ulink" href="https://wiki.yoctoproject.org/wiki/Transcript:_from_git_checkout_to_meta-intel_BSP" target="_top">
wiki page</a> referenced earlier covers how to
set up the <code class="filename">meta-intel</code> Git repository.</p></li></ul></div></li><li class="listitem"><p><span class="emphasis"><em>Eclipse Yocto Plug-in:</em></span> If you are developing
applications using the Eclipse Integrated Development Environment (IDE),
you will need this plug-in.
See the
"<a class="link" href="#setting-up-the-eclipse-ide" title="5.2.2.1. Setting Up the Eclipse IDE">Setting up the Eclipse IDE</a>"
section for more information.</p></li></ul></div><p>
</p></div><div class="section" title="2.3. Building Images"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="building-images"></a>2.3. Building Images</h2></div></div></div><p>
The build process creates an entire Linux distribution, including the toolchain, from source.
For more information on this topic, see the
"<a class="link" href="#building-image" target="_top">Building an Image</a>"
section in the Yocto Project Quick Start.
</p><p>
The build process is as follows:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Make sure you have set up the source directory described in the
previous section.</p></li><li class="listitem"><p>Initialize the build environment by sourcing a build environment
script.</p></li><li class="listitem"><p>Optionally ensure the <code class="filename">conf/local.conf</code> configuration file,
which is found in the
<a class="link" href="#build-directory">build directory</a>,
is set up how you want it.
This file defines many aspects of the build environment including
the target machine architecture through the
<code class="filename"><a class="link" href="#var-MACHINE" target="_top">MACHINE</a></code> variable,
the development machine's processor use through the
<code class="filename"><a class="link" href="#var-BB_NUMBER_THREADS" target="_top">BB_NUMBER_THREADS</a></code> and
<code class="filename"><a class="link" href="#var-PARALLEL_MAKE" target="_top">PARALLEL_MAKE</a></code> variables, and
a centralized tarball download directory through the
<code class="filename"><a class="link" href="#var-DL_DIR" target="_top">DL_DIR</a></code> variable.</p></li><li class="listitem"><p>Build the image using the <code class="filename">bitbake</code> command.
If you want information on BitBake, see the user manual at
<a class="ulink" href="http://docs.openembedded.org/bitbake/html" target="_top">http://docs.openembedded.org/bitbake/html</a>.</p></li><li class="listitem"><p>Run the image either on the actual hardware or using the QEMU
emulator.</p></li></ol></div><p>
</p></div><div class="section" title="2.4. Using Pre-Built Binaries and QEMU"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="using-pre-built-binaries-and-qemu"></a>2.4. Using Pre-Built Binaries and QEMU</h2></div></div></div><p>
Another option you have to get started is to use pre-built binaries.
The Yocto Project provides many types of binaries with each release.
See the <a class="link" href="#ref-images" target="_top">Images</a>
chapter in the Yocto Project Reference Manual
for descriptions of the types of binaries that ship with a Yocto Project
release.
</p><p>
Using a pre-built binary is ideal for developing software applications to run on your
target hardware.
To do this, you need to be able to access the appropriate cross-toolchain tarball for
the architecture on which you are developing.
If you are using an SDK type image, the image ships with the complete toolchain native to
the architecture.
If you are not using an SDK type image, you need to separately download and
install the stand-alone Yocto Project cross-toolchain tarball.
</p><p>
Regardless of the type of image you are using, you need to download the pre-built kernel
that you will boot in the QEMU emulator and then download and extract the target root
filesystem for your target machine’s architecture.
You can get architecture-specific binaries and filesystem from
<a class="ulink" href="http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/machines" target="_top">machines</a>.
You can get stand-alone toolchains from
<a class="ulink" href="http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/toolchain/" target="_top">toolchains</a>.
Once you have all your files, you set up the environment to emulate the hardware
by sourcing an environment setup script.
Finally, you start the QEMU emulator.
You can find details on all these steps in the
"<a class="link" href="#using-pre-built" target="_top">Using Pre-Built Binaries and QEMU</a>"
section of the Yocto Project Quick Start.
</p><p>
Using QEMU to emulate your hardware can result in speed issues
depending on the target and host architecture mix.
For example, using the <code class="filename">qemux86</code> image in the emulator
on an Intel-based 32-bit (x86) host machine is fast because the target and
host architectures match.
On the other hand, using the <code class="filename">qemuarm</code> image on the same Intel-based
host can be slower.
But, you still achieve faithful emulation of ARM-specific issues.
</p><p>
To speed things up, the QEMU images support using <code class="filename">distcc</code>
to call a cross-compiler outside the emulated system.
If you used <code class="filename">runqemu</code> to start QEMU, and the
<code class="filename">distccd</code> application is present on the host system, any
BitBake cross-compiling toolchain available from the build system is automatically
used from within QEMU simply by calling <code class="filename">distcc</code>.
You can accomplish this by defining the cross-compiler variable
(e.g. <code class="filename">export CC="distcc"</code>).
Alternatively, if you are using a suitable SDK image or the appropriate
stand-alone toolchain is present in <code class="filename">/opt/poky</code>,
the toolchain is also automatically used.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Several mechanisms exist that let you connect to the system running on the
QEMU emulator:
<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>QEMU provides a framebuffer interface that makes standard
consoles available.</p></li><li class="listitem"><p>Generally, headless embedded devices have a serial port.
If so, you can configure the operating system of the running image
to use that port to run a console.
The connection uses standard IP networking.</p></li><li class="listitem"><p>SSH servers exist in some QEMU images.
The <code class="filename">core-image-sato</code> QEMU image has a Dropbear secure
shell (ssh) server that runs with the root password disabled.
The <code class="filename">core-image-basic</code> and <code class="filename">core-image-lsb</code> QEMU images
have OpenSSH instead of Dropbear.
Including these SSH servers allow you to use standard <code class="filename">ssh</code> and
<code class="filename">scp</code> commands.
The <code class="filename">core-image-minimal</code> QEMU image, however, contains no ssh
server.</p></li><li class="listitem"><p>You can use a provided, user-space NFS server to boot the QEMU session
using a local copy of the root filesystem on the host.
In order to make this connection, you must extract a root filesystem tarball by using the
<code class="filename">runqemu-extract-sdk</code> command.
After running the command, you must then point the <code class="filename">runqemu</code>
script to the extracted directory instead of a root filesystem image file.</p></li></ul></div></div></div></div>
<div class="chapter" title="Chapter 3. The Yocto Project Open Source Development Environment"><div class="titlepage"><div><div><h2 class="title"><a id="dev-manual-newbie"></a>Chapter 3. The Yocto Project Open Source Development Environment</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#open-source-philosophy">3.1. Open Source Philosophy</a></span></dt><dt><span class="section"><a href="#usingpoky-changes-collaborate">3.2. Using the Yocto Project in a Team Environment</a></span></dt><dt><span class="section"><a href="#yocto-project-repositories">3.3. Yocto Project Source Repositories</a></span></dt><dt><span class="section"><a href="#yocto-project-terms">3.4. Yocto Project Terms</a></span></dt><dt><span class="section"><a href="#licensing">3.5. Licensing</a></span></dt><dt><span class="section"><a href="#git">3.6. Git</a></span></dt><dd><dl><dt><span class="section"><a href="#repositories-tags-and-branches">3.6.1. Repositories, Tags, and Branches</a></span></dt><dt><span class="section"><a href="#basic-commands">3.6.2. Basic Commands</a></span></dt></dl></dd><dt><span class="section"><a href="#workflows">3.7. Workflows</a></span></dt><dt><span class="section"><a href="#tracking-bugs">3.8. Tracking Bugs</a></span></dt><dt><span class="section"><a href="#how-to-submit-a-change">3.9. How to Submit a Change</a></span></dt><dd><dl><dt><span class="section"><a href="#pushing-a-change-upstream">3.9.1. Using Scripts to Push a Change Upstream and Request a Pull</a></span></dt><dt><span class="section"><a href="#submitting-a-patch">3.9.2. Using Email to Submit a Patch</a></span></dt></dl></dd></dl></div><p>
This chapter helps you understand the Yocto Project as an open source development project.
In general, working in an open source environment is very different from working in a
closed, proprietary environment.
Additionally, the Yocto Project uses specific tools and constructs as part of its development
environment.
This chapter specifically addresses open source philosophy, licensing issues, code repositories,
the open source distributed version control system Git, and best practices using the Yocto Project.
</p><div class="section" title="3.1. Open Source Philosophy"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="open-source-philosophy"></a>3.1. Open Source Philosophy</h2></div></div></div><p>
Open source philosophy is characterized by software development directed by peer production
and collaboration through an active community of developers.
Contrast this to the more standard centralized development models used by commercial software
companies where a finite set of developers produces a product for sale using a defined set
of procedures that ultimately result in an end product whose architecture and source material
are closed to the public.
</p><p>
Open source projects conceptually have differing concurrent agendas, approaches, and production.
These facets of the development process can come from anyone in the public (community) that has a
stake in the software project.
The open source environment contains new copyright, licensing, domain, and consumer issues
that differ from the more traditional development environment.
In an open source environment, the end product, source material, and documentation are
all available to the public at no cost.
</p><p>
A benchmark example of an open source project is the Linux Kernel, which was initially conceived
and created by Finnish computer science student Linus Torvalds in 1991.
Conversely, a good example of a non-open source project is the
<span class="trademark">Windows</span>® family of operating
systems developed by <span class="trademark">Microsoft</span>® Corporation.
</p><p>
Wikipedia has a good historical description of the Open Source Philosophy
<a class="ulink" href="http://en.wikipedia.org/wiki/Open_source" target="_top">here</a>.
You can also find helpful information on how to participate in the Linux Community
<a class="ulink" href="http://ldn.linuxfoundation.org/book/how-participate-linux-community" target="_top">here</a>.
</p></div><div class="section" title="3.2. Using the Yocto Project in a Team Environment"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="usingpoky-changes-collaborate"></a>3.2. Using the Yocto Project in a Team Environment</h2></div></div></div><p>
It might not be immediately clear how you can use the Yocto Project in a team environment,
or scale it for a large team of developers.
The specifics of any situation determine the best solution.
Granted that the Yocto Project offers immense flexibility regarding this, practices do exist
that experience has shown work well.
</p><p>
The core component of any development effort with the Yocto Project is often an
automated build and testing framework along with an image generation process.
You can use these core components to check that the metadata can be built,
highlight when commits break the build, and provide up-to-date images that
allow developers to test the end result and use it as a base platform for further
development.
Experience shows that buildbot is a good fit for this role.
What works well is to configure buildbot to make two types of builds:
incremental and full (from scratch).
See <a class="ulink" href="http://autobuilder.yoctoproject.org:8010/" target="_top">the buildbot for the
Yocto Project</a> for an example implementation that uses buildbot.
</p><p>
You can tie incremental builds to a commit hook that triggers the build
each time a commit is made to the metadata.
This practice results in useful acid tests that determine whether a given commit
breaks the build in some serious way.
Associating a build to a commit can catch a lot of simple errors.
Furthermore, the tests are fast so developers can get quick feedback on changes.
</p><p>
Full builds build and test everything from the ground up.
These types of builds usually happen at predetermined times like during the
night when the machine load is low.
</p><p>
Most teams have many pieces of software undergoing active development at any given time.
You can derive large benefits by putting these pieces under the control of a source
control system that is compatible (i.e. Git or Subversion (SVN)) with the OpenEmbeded
build system that the Yocto Project uses.
You can then set the autobuilder to pull the latest revisions of the packages
and test the latest commits by the builds.
This practice quickly highlights issues.
The build system easily supports testing configurations that use both a
stable known good revision and a floating revision.
The build system can also take just the changes from specific source control branches.
This capability allows you to track and test specific changes.
</p><p>
Perhaps the hardest part of setting this up is defining the software project or
the metadata policies that surround the different source control systems.
Of course circumstances will be different in each case.
However, this situation reveals one of the Yocto Project's advantages -
the system itself does not
force any particular policy on users, unlike a lot of build systems.
The system allows the best policies to be chosen for the given circumstances.
</p></div><div class="section" title="3.3. Yocto Project Source Repositories"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="yocto-project-repositories"></a>3.3. Yocto Project Source Repositories</h2></div></div></div><p>
The Yocto Project team maintains complete source repositories for all Yocto Project files
at <a class="ulink" href="http://git.yoctoproject.org/cgit/cgit.cgi" target="_top">http://git.yoctoproject.org/cgit/cgit.cgi</a>.
This web-based source code browser is organized into categories by function such as
IDE Plugins, Matchbox, Poky, Yocto Linux Kernel, and so forth.
From the interface, you can click on any particular item in the "Name" column and
see the URL at the bottom of the page that you need to set up a Git repository for
that particular item.
Having a local Git repository of the source directory (poky) allows you to
make changes, contribute to the history, and ultimately enhance the Yocto Project's
tools, Board Support Packages, and so forth.
</p><p>
Conversely, if you are a developer that is not interested in contributing back to the
Yocto Project, you have the ability to simply download and extract release tarballs
and use them within the Yocto Project environment.
All that is required is a particular release of the Yocto Project and
your application source code.
</p><p>
For any supported release of Yocto Project, you can go to the Yocto Project website’s
<a class="ulink" href="http://www.yoctoproject.org/download" target="_top">download page</a> and get a
tarball of the release.
You can also go to this site to download any supported BSP tarballs.
Unpacking the tarball gives you a hierarchical source directory that lets you develop
using the Yocto Project.
</p><p>
Once you are set up through either tarball extraction or creation of Git repositories,
you are ready to develop.
</p><p>
In summary, here is where you can get the project files needed for development:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><a id="source-repositories"></a><span class="emphasis"><em><a class="ulink" href="http://git.yoctoproject.org/cgit/cgit.cgi" target="_top">Source Repositories:</a></em></span>
This area contains IDE Plugins, Matchbox, Poky, Poky Support, Tools, Yocto Linux Kernel, and Yocto
Metadata Layers.
You can create local copies of Git repositories for each of these areas.</p><p>
</p><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr style="height: 360px"><td align="center"><img src="figures/source-repos.png" align="middle" width="540" /></td></tr></table><p>
</p></li><li class="listitem"><p><a id="index-downloads"></a><span class="emphasis"><em><a class="ulink" href="http://downloads.yoctoproject.org/releases/" target="_top">Index of /releases:</a></em></span>
This area contains index releases such as
the <span class="trademark">Eclipse</span>™
Yocto Plug-in, miscellaneous support, poky, pseudo, cross-development toolchains,
and all released versions of Yocto Project in the form of images or tarballs.
Downloading and extracting these files does not produce a local copy of the
Git repository but rather a snapshot of a particular release or image.</p><p>
</p><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr style="height: 360px"><td align="center"><img src="figures/index-downloads.png" align="middle" width="540" /></td></tr></table><p>
</p></li><li class="listitem"><p><span class="emphasis"><em><a class="ulink" href="http://www.yoctoproject.org/download" target="_top">Yocto Project Download Page</a></em></span>
This page on the Yocto Project website allows you to download any Yocto Project
release or Board Support Package (BSP) in tarball form.
The tarballs are similar to those found in the
<a class="ulink" href="http://downloads.yoctoproject.org/releases/" target="_top">Index of /releases:</a> area.</p><p>
</p><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr style="height: 360px"><td align="center"><img src="figures/yp-download.png" align="middle" width="540" /></td></tr></table><p>
</p></li></ul></div><p>
</p></div><div class="section" title="3.4. Yocto Project Terms"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="yocto-project-terms"></a>3.4. Yocto Project Terms</h2></div></div></div><p>
Following is a list of terms and definitions users new to the Yocto Project development
environment might find helpful.
While some of these terms are universal, the list includes them just in case:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Append Files:</em></span> Files that append build information to
a recipe file.
Append files are known as BitBake append files and <code class="filename">.bbappend</code> files.
The OpenEmbedded build system expects every append file to have a corresponding and
underlying recipe (<code class="filename">.bb</code>) file.
Furthermore, the append file and the underlying recipe must have the same root filename.
The filenames can differ only in the file type suffix used (e.g.
<code class="filename">formfactor_0.0.bb</code> and <code class="filename">formfactor_0.0.bbappend</code>).
</p><p>Information in append files overrides the information in the similarly-named recipe file.
For examples of <code class="filename">.bbappend</code> file in use, see the
"<a class="link" href="#using-bbappend-files" title="4.1.4. Using .bbappend Files">Using .bbappend Files</a>" and
"<a class="link" href="#changing-recipes-kernel" title="A.5.2.4. Changing  recipes-kernel">Changing <code class="filename">recipes-kernel</code></a>"
sections.</p></li><li class="listitem"><p><span class="emphasis"><em>BitBake:</em></span> The task executor and scheduler used by
the OpenEmbedded build system to build images.
For more information on BitBake, see the <a class="ulink" href="http://docs.openembedded.org/bitbake/html/" target="_top">
BitBake documentation</a>.</p></li><li class="listitem"><p><a id="build-directory"></a><span class="emphasis"><em>Build Directory:</em></span>
This term refers to the area used by the OpenEmbedded build system for builds.
The area is created when you <code class="filename">source</code> the setup
environment script that is found in the source directory
(i.e. <code class="filename">oe-init-build-env</code>).
The <a class="link" href="#var-TOPDIR" target="_top"><code class="filename">TOPDIR</code></a>
variable points to the build directory.</p><p>You have a lot of flexibility when creating the build directory.
Following are some examples that show how to create the directory:
</p><div class="itemizedlist"><ul class="itemizedlist" type="circle"><li class="listitem"><p>Create the build directory in your current working directory
and name it <code class="filename">build</code>.
This is the default behavior.
</p><pre class="literallayout">
$ source oe-init-build-env
</pre></li><li class="listitem"><p>Provide a directory path and specifically name the build
directory.
This next example creates a build directory named <code class="filename">YP-8.0</code>
in your home directory within the directory <code class="filename">mybuilds</code>.
If <code class="filename">mybuilds</code> does not exist, the directory is created for you:
</p><pre class="literallayout">
$ source poky-1.2+snapshot-8.0/oe-init-build-env $HOME/mybuilds/YP-8.0
</pre></li><li class="listitem"><p>Provide an existing directory to use as the build directory.
This example uses the existing <code class="filename">mybuilds</code> directory
as the build directory.
</p><pre class="literallayout">
$ source poky-1.2+snapshot-8.0/oe-init-build-env $HOME/mybuilds/
</pre></li></ul></div><p>
</p></li><li class="listitem"><p><span class="emphasis"><em>Build System:</em></span> In the context of the Yocto Project
this term refers to the OpenEmbedded build system used by the project.
This build system is based on the project known as "Poky."
For some historical information about Poky, see the
<a class="link" href="#poky">poky</a> term further along in this section.
</p></li><li class="listitem"><p><span class="emphasis"><em>Classes:</em></span> Files that provide for logic encapsulation
and inheritance allowing commonly used patterns to be defined once and easily used
in multiple recipes.
Class files end with the <code class="filename">.bbclass</code> filename extension.
</p></li><li class="listitem"><p><span class="emphasis"><em>Configuration File:</em></span> Configuration information in various
<code class="filename">.conf</code> files provides global definitions of variables.
The <code class="filename">conf/local.conf</code> configuration file in the
<a class="link" href="#build-directory">build directory</a>
contains user-defined variables that affect each build.
The <code class="filename">meta-yocto/conf/distro/poky.conf</code> configuration file
defines Yocto ‘distro’ configuration
variables used only when building with this policy.
Machine configuration files, which
are located throughout the
<a class="link" href="#source-directory">source directory</a>, define
variables for specific hardware and are only used when building for that target
(e.g. the <code class="filename">machine/beagleboard.conf</code> configuration file defines
variables for the Texas Instruments ARM Cortex-A8 development board).
Configuration files end with a <code class="filename">.conf</code> filename extension.
</p></li><li class="listitem"><p><span class="emphasis"><em>Cross-Development Toolchain:</em></span>
A collection of software development
tools and utilities that allow you to develop software for targeted architectures.
This toolchain contains cross-compilers, linkers, and debuggers that are specific to
an architecture.
You can use the OpenEmbedded build system to build cross-development toolchains in tarball
form that, when
unpacked, contain the development tools you need to cross-compile and test your software.
The Yocto Project ships with images that contain toolchains for supported architectures
as well.
Sometimes this toolchain is referred to as the meta-toolchain.</p></li><li class="listitem"><p><span class="emphasis"><em>Image:</em></span> An image is the result produced when
BitBake processes a given collection of recipes and related metadata.
Images are the binary output that run on specific hardware and for specific
use cases.
For a list of the supported image types that the Yocto Project provides, see the
"<a class="link" href="#ref-images" target="_top">Images</a>"
chapter in the Yocto Project Reference Manual.</p></li><li class="listitem"><p><a id="layer"></a><span class="emphasis"><em>Layer:</em></span> A collection of recipes representing the core,
a BSP, or an application stack.
For a discussion on BSP Layers, see the
"<a class="link" href="#bsp-layers" target="_top">BSP Layers</a>"
section in the Yocto Project Board Support Packages (BSP) Developer's Guide.</p></li><li class="listitem"><p><a id="metadata"></a><span class="emphasis"><em>Metadata:</em></span> The files that BitBake parses when
building an image.
Metadata includes recipes, classes, and configuration files.</p></li><li class="listitem"><p><span class="emphasis"><em>OE-Core:</em></span> A core set of metadata originating
with OpenEmbedded (OE) that is shared between OE and the Yocto Project.
This metadata is found in the <code class="filename">meta</code> directory of the source
directory.</p></li><li class="listitem"><p><span class="emphasis"><em>Package:</em></span> The packaged output from a baked recipe.
A package is generally the compiled binaries produced from the recipe's sources.
You ‘bake’ something by running it through BitBake.</p></li><li class="listitem"><p><a id="poky"></a><span class="emphasis"><em>Poky:</em></span> The term "poky" can mean several things.
In its most general sence, it is an open-source project that was initially developed
by OpenedHand. With OpenedHand, poky was developed off of the existing OpenEmbedded
build system becoming a build system for embedded images.
After Intel Corporation aquired OpenedHand, the project poky became the basis for
the Yocto Project's build system.
Within the Yocto Project source repositories, poky exists as a separate Git repository
that can be cloned to yield a local copy on the host system.
Thus, "poky" can refer to the local copy of the source directory used to develop within
the Yocto Project.</p></li><li class="listitem"><p><span class="emphasis"><em>Recipe:</em></span> A set of instructions for building packages.
A recipe describes where you get source code and which patches to apply.
Recipes describe dependencies for libraries or for other recipes, and they
also contain configuration and compilation options.
Recipes contain the logical unit of execution, the software/images to build, and
use the <code class="filename">.bb</code> file extension.</p></li><li class="listitem"><p><a id="source-directory"></a><span class="emphasis"><em>Source Directory:</em></span>
This term refers to the directory structure created as a result of either downloading
and unpacking a Yocto Project release tarball or creating a local copy of
<code class="filename">poky</code> Git repository <code class="filename">git://git.yoctoproject.org/poky</code>.
Sometimes you might here the term "poky directory" used to refer to this
directory structure.</p><p>The source directory contains BitBake, Documentation, metadata and
other files that all support the Yocto Project.
Consequently, you must have the source directory in place on your development
system in order to do any development using the Yocto Project.</p><p>For tarball expansion, the name of the top-level directory of the source directory
is derived from the Yocto Project release tarball.
For example, downloading and unpacking <code class="filename">poky-1.2+snapshot-8.0.tar.bz2</code>
results in a source directory whose top-level folder is named
<code class="filename">poky-1.2+snapshot-8.0</code>.
If you create a local copy of the Git repository, then you can name the repository
anything you like.
Throughout much of the documentation, <code class="filename">poky</code> is used as the name of
the top-level folder of the local copy of the poky Git repository.
So, for example, cloning the <code class="filename">poky</code> Git repository results in a
local Git repository whose top-level folder is also named <code class="filename">poky</code>.</p><p>It is important to understand the differences between the source directory created
by unpacking a released tarball as compared to cloning
<code class="filename">git://git.yoctoproject.org/poky</code>.
When you unpack a tarball, you have an exact copy of the files based on the time of
release - a fixed release point.
Any changes you make to your local files in the source directory are on top of the release.
On the other hand, when you clone the <code class="filename">poky</code> Git repository, you have an
active development repository.
In this case, any local changes you make to the source directory can be later applied
to active development branches of the upstream <code class="filename">poky</code> Git
repository.</p><p>Finally, if you want to track a set of local changes while starting from the same point
as a release tarball, you can create a local Git branch that
reflects the exact copy of the files at the time of their release.
You do this using Git tags that are part of the repository.</p><p>For more information on concepts around Git repositories, branches, and tags,
see the
"<a class="link" href="#repositories-tags-and-branches" title="3.6.1. Repositories, Tags, and Branches">Repositories, Tags, and Branches</a>"
section.</p></li><li class="listitem"><p><span class="emphasis"><em>Tasks:</em></span> Arbitrary groups of software Recipes.
You simply use Tasks to hold recipes that, when built, usually accomplish a single task.
For example, a task could contain the recipes for a company’s proprietary or value-add software.
Or, the task could contain the recipes that enable graphics.
A task is really just another recipe.
Because task files are recipes, they end with the <code class="filename">.bb</code> filename
extension.</p></li><li class="listitem"><p><span class="emphasis"><em>Upstream:</em></span> A reference to source code or repositories
that are not local to the development system but located in a master area that is controlled
by the maintainer of the source code.
For example, in order for a developer to work on a particular piece of code, they need to
first get a copy of it from an "upstream" source.</p></li></ul></div><p>
</p></div><div class="section" title="3.5. Licensing"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="licensing"></a>3.5. Licensing</h2></div></div></div><p>
Because open source projects are open to the public, they have different licensing structures in place.
License evolution for both Open Source and Free Software has an interesting history.
If you are interested in this history, you can find basic information here:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><a class="ulink" href="http://en.wikipedia.org/wiki/Open-source_license" target="_top">Open source license history</a>
</p></li><li class="listitem"><p><a class="ulink" href="http://en.wikipedia.org/wiki/Free_software_license" target="_top">Free software license
history</a></p></li></ul></div><p>
</p><p>
In general, the Yocto Project is broadly licensed under the Massachusetts Institute of Technology
(MIT) License.
MIT licensing permits the reuse of software within proprietary software as long as the
license is distributed with that software.
MIT is also compatible with the GNU General Public License (GPL).
Patches to the Yocto Project follow the upstream licensing scheme.
You can find information on the MIT license at
<a class="ulink" href="http://www.opensource.org/licenses/mit-license.php" target="_top">here</a>.
You can find information on the GNU GPL <a class="ulink" href="http://www.opensource.org/licenses/LGPL-3.0" target="_top">
here</a>.
</p><p>
When you build an image using Yocto Project, the build process uses a known list of licenses to
ensure compliance.
You can find this list in the Yocto Project files directory at
<code class="filename">meta/files/common-licenses</code>.
Once the build completes, the list of all licenses found and used during that build are
kept in the
<a class="link" href="#build-directory">build directory</a> at
<code class="filename">tmp/deploy/images/licenses</code>.
</p><p>
If a module requires a license that is not in the base list, the build process
generates a warning during the build.
These tools make it easier for a developer to be certain of the licenses with which
their shipped products must comply.
However, even with these tools it is still up to the developer to resolve potential licensing issues.
</p><p>
The base list of licenses used by the build process is a combination of the Software Package
Data Exchange (SPDX) list and the Open Source Initiative (OSI) projects.
<a class="ulink" href="http://spdx.org" target="_top">SPDX Group</a> is a working group of the Linux Foundation
that maintains a specification
for a standard format for communicating the components, licenses, and copyrights
associated with a software package.
<a class="ulink" href="http://opensource.org" target="_top">OSI</a> is a corporation dedicated to the Open Source
Definition and the effort for reviewing and approving licenses that are OSD-conformant.
</p><p>
You can find a list of the combined SPDX and OSI licenses that the Yocto Project uses
<a class="ulink" href="http://git.yoctoproject.org/cgit/cgit.cgi/poky/tree/meta/files/common-licenses" target="_top">here</a>.
This wiki page discusses the license infrastructure used by the Yocto Project.
</p></div><div class="section" title="3.6. Git"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="git"></a>3.6. Git</h2></div></div></div><p>
The Yocto Project uses Git, which is a free, open source distributed version control system.
Git supports distributed development, non-linear development, and can handle large projects.
It is best that you have some fundamental understanding of how Git tracks projects and
how to work with Git if you are going to use Yocto Project for development.
This section provides a quick overview of how Git works and provides you with a summary
of some essential Git commands.
</p><p>
For more information on Git, see
<a class="ulink" href="http://git-scm.com/documentation" target="_top">http://git-scm.com/documentation</a>.
If you need to download Git, go to <a class="ulink" href="http://git-scm.com/download" target="_top">http://git-scm.com/download</a>.
</p><div class="section" title="3.6.1. Repositories, Tags, and Branches"><div class="titlepage"><div><div><h3 class="title"><a id="repositories-tags-and-branches"></a>3.6.1. Repositories, Tags, and Branches</h3></div></div></div><p>
As mentioned earlier in section
"<a class="link" href="#yocto-project-repositories" title="3.3. Yocto Project Source Repositories">Yocto Project Source Repositories</a>",
the Yocto Project maintains source repositories at
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi" target="_top">http://git.yoctoproject.org/cgit.cgi</a>.
If you look at this web-interface of the repositories, each item is a separate
Git repository.
</p><p>
Git repositories use branching techniques that track content change (not files)
within a project (e.g. a new feature or updated documentation).
Creating a tree-like structure based on project divergence allows for excellent historical
information over the life of a project.
This methodology also allows for an environment in which you can do lots of
local experimentation on a project as you develop changes or new features.
</p><p>
A Git repository represents all development efforts for a given project.
For example, the Git repository <code class="filename">poky</code> contains all changes
and developments for Poky over the course of its entire life.
That means that all changes that make up all releases are captured.
The repository maintains a complete history of changes.
</p><p>
You can create a local copy of any repository by "cloning" it with the Git
<code class="filename">clone</code> command.
When you clone a Git repository, you end up with an identical copy of the
repository on your development system.
Once you have a local copy of a repository, you can take steps to develop locally.
For examples on how to clone Git repositories, see the section
"<a class="link" href="#getting-setup" title="2.2. Getting Set Up">Getting Set Up</a>" earlier in this manual.
</p><p>
It is important to understand that Git tracks content change and not files.
Git uses "branches" to organize different development efforts.
For example, the <code class="filename">poky</code> repository has
<code class="filename">laverne</code>, <code class="filename">bernard</code>,
<code class="filename">edison</code>, <code class="filename">denzil</code> and
<code class="filename">master</code> branches among
others.
You can see all the branches by going to
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi/poky/" target="_top">http://git.yoctoproject.org/cgit.cgi/poky/</a> and
clicking on the
<code class="filename"><a class="ulink" href="http://git.yoctoproject.org/cgit.cgi/poky/refs/heads" target="_top">[...]</a></code>
link beneath the "Branch" heading.
</p><p>
Each of these branches represents a specific area of development.
The <code class="filename">master</code> branch represents the current or most recent
development.
All other branches represent off-shoots of the <code class="filename">master</code>
branch.
</p><p>
When you create a local copy of a Git repository, the copy has the same set
of branches as the original.
This means you can use Git to create a local working area (also called a branch)
that tracks a specific development branch from the source Git repository.
in other words, you can define your local Git environment to work on any development
branch in the repository.
To help illustrate, here is a set of commands that creates a local copy of the
<code class="filename">poky</code> Git repository and then creates and checks out a local
Git branch that tracks the Yocto Project 1.3 Release (1.2+snapshot) development:
</p><pre class="literallayout">
$ cd ~
$ git clone git://git.yoctoproject.org/poky
$ cd poky
$ git checkout -b 1.2+snapshot origin/1.2+snapshot
</pre><p>
In this example, the name of the top-level directory of your local Yocto Project
Files Git repository is <code class="filename">poky</code>,
and the name of the local working area (or local branch) you have created and checked
out is <code class="filename">1.2+snapshot</code>.
The files in your repository now reflect the same files that are in the
<code class="filename">1.2+snapshot</code> development branch of the Yocto Project's
<code class="filename">poky</code> repository.
It is important to understand that when you create and checkout a
local working branch based on a branch name,
your local environment matches the "tip" of that development branch
at the time you created your local branch, which could be
different than the files at the time of a similarly named release.
In other words, creating and checking out a local branch based on the
<code class="filename">1.2+snapshot</code> branch name is not the same as creating and
checking out a local branch based on the <code class="filename">1.2+snapshot-1.3</code>
release.
Keep reading to see how you create a local snapshot of a Yocto Project Release.
</p><p>
Git uses "tags" to mark specific changes in a repository.
Typically, a tag is used to mark a special point such as the final change
before a project is released.
You can see the tags used with the <code class="filename">poky</code> Git repository
by going to <a class="ulink" href="http://git.yoctoproject.org/cgit.cgi/poky/" target="_top">http://git.yoctoproject.org/cgit.cgi/poky/</a> and
clicking on the
<code class="filename"><a class="ulink" href="http://git.yoctoproject.org/cgit.cgi/poky/refs/tags" target="_top">[...]</a></code>
link beneath the "Tag" heading.
</p><p>
Some key tags are <code class="filename">laverne-4.0</code>, <code class="filename">bernard-5.0</code>,
and <code class="filename">1.2+snapshot-8.0</code>.
These tags represent Yocto Project releases.
</p><p>
When you create a local copy of the Git repository, you also have access to all the
tags.
Similar to branches, you can create and checkout a local working Git branch based
on a tag name.
When you do this, you get a snapshot of the Git repository that reflects
the state of the files when the change was made associated with that tag.
The most common use is to checkout a working branch that matches a specific
Yocto Project release.
Here is an example:
</p><pre class="literallayout">
$ cd ~
$ git clone git://git.yoctoproject.org/poky
$ cd poky
$ git checkout -b my-1.2+snapshot-8.0 1.2+snapshot-8.0
</pre><p>
In this example, the name of the top-level directory of your local Yocto Project
Files Git repository is <code class="filename">poky</code>.
And, the name of the local branch you have created and checked out is
<code class="filename">my-1.2+snapshot-8.0</code>.
The files in your repository now exactly match the Yocto Project 1.3
Release tag (<code class="filename">1.2+snapshot-8.0</code>).
It is important to understand that when you create and checkout a local
working branch based on a tag, your environment matches a specific point
in time and not a development branch.
</p></div><div class="section" title="3.6.2. Basic Commands"><div class="titlepage"><div><div><h3 class="title"><a id="basic-commands"></a>3.6.2. Basic Commands</h3></div></div></div><p>
Git has an extensive set of commands that lets you manage changes and perform
collaboration over the life of a project.
Conveniently though, you can manage with a small set of basic operations and workflows
once you understand the basic philosophy behind Git.
You do not have to be an expert in Git to be functional.
A good place to look for instruction on a minimal set of Git commands is
<a class="ulink" href="http://git-scm.com/documentation" target="_top">here</a>.
If you need to download Git, you can do so
<a class="ulink" href="http://git-scm.com/download" target="_top">here</a>.
</p><p>
If you don’t know much about Git, we suggest you educate
yourself by visiting the links previously mentioned.
</p><p>
The following list briefly describes some basic Git operations as a way to get started.
As with any set of commands, this list (in most cases) simply shows the base command and
omits the many arguments they support.
See the Git documentation for complete descriptions and strategies on how to use these commands:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><code class="filename">git init</code>:</em></span> Initializes an empty Git repository.
You cannot use Git commands unless you have a <code class="filename">.git</code> repository.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">git clone</code>:</em></span> Creates a clone of a repository.
During collaboration, this command allows you to create a local repository that is on
equal footing with a fellow developer’s repository.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">git add</code>:</em></span> Adds updated file contents
to the index that
Git uses to track changes.
You must add all files that have changed before you can commit them.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">git commit</code>:</em></span> Creates a “commit” that documents
the changes you made.
Commits are used for historical purposes, for determining if a maintainer of a project
will allow the change, and for ultimately pushing the change from your local Git repository
into the project’s upstream (or master) repository.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">git status</code>:</em></span> Reports any modified files that
possibly need to be added and committed.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">git checkout &lt;branch-name&gt;</code>:</em></span> Changes
your working branch.
This command is analogous to “cd”.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">git checkout –b &lt;working-branch&gt;</code>:</em></span> Creates
a working branch on your local machine where you can isolate work.
It is a good idea to use local branches when adding specific features or changes.
This way if you don’t like what you have done you can easily get rid of the work.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">git branch</code>:</em></span> Reports existing branches and
tells you which branch in which you are currently working.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">git branch -D &lt;branch-name&gt;</code>:</em></span>
Deletes an existing branch.
You need to be in a branch other than the one you are deleting
in order to delete &lt;branch-name&gt;.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">git pull</code>:</em></span> Retrieves information
from an upstream Git
repository and places it in your local Git repository.
You use this command to make sure you are synchronized with the repository
from which you are basing changes (.e.g. the master repository).</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">git push</code>:</em></span> Sends all your local changes you
have committed to an upstream Git repository (e.g. a contribution repository).
The maintainer of the project draws from these repositories when adding your changes to the
project’s master repository.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">git merge</code>:</em></span> Combines or adds changes from one
local branch of your repository with another branch.
When you create a local Git repository, the default branch is named “master”.
A typical workflow is to create a temporary branch for isolated work, make and commit your
changes, switch to your local master branch, merge the changes from the temporary branch into the
local master branch, and then delete the temporary branch.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">git cherry-pick</code>:</em></span> Choose and apply specific
commits from one branch into another branch.
There are times when you might not be able to merge all the changes in one branch with
another but need to pick out certain ones.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">gitk</code>:</em></span> Provides a GUI view of the branches
and changes in your local Git repository.
This command is a good way to graphically see where things have diverged in your
local repository.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">git log</code>:</em></span> Reports a history of your changes to the
repository.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">git diff</code>:</em></span> Displays line-by-line differences
between your local working files and the same files in the upstream Git repository that your
branch currently tracks.</p></li></ul></div><p>
</p></div></div><div class="section" title="3.7. Workflows"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="workflows"></a>3.7. Workflows</h2></div></div></div><p>
This section provides some overview on workflows using Git.
In particular, the information covers basic practices that describe roles and actions in a
collaborative development environment.
Again, if you are familiar with this type of development environment, you might want to just
skip this section.
</p><p>
The Yocto Project files are maintained using Git in a "master" branch whose Git history
tracks every change and whose structure provides branches for all diverging functionality.
Although there is no need to use Git, many open source projects do so.
For the Yocto Project, a key individual called the "maintainer" is responsible for the "master"
branch of the Git repository.
The "master" branch is the “upstream” repository where the final builds of the project occur.
The maintainer is responsible for allowing changes in from other developers and for
organizing the underlying branch structure to reflect release strategies and so forth.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>You can see who is the maintainer for Yocto Project files by examining the
<code class="filename">distro_tracking_fields.inc</code> file in the Yocto Project
<code class="filename">meta/conf/distro/include</code> directory.</div><p>
</p><p>
The project also has contribution repositories known as “contrib” areas.
These areas temporarily hold changes to the project that have been submitted or committed
by the Yocto Project development team and by community members that contribute to the project.
The maintainer determines if the changes are qualified to be moved from the "contrib" areas
into the "master" branch of the Git repository.
</p><p>
Developers (including contributing community members) create and maintain cloned repositories
of the upstream "master" branch.
These repositories are local to their development platforms and are used to develop changes.
When a developer is satisfied with a particular feature or change, they “push” the changes
to the appropriate "contrib" repository.
</p><p>
Developers are responsible for keeping their local repository up-to-date with "master".
They are also responsible for straightening out any conflicts that might arise within files
that are being worked on simultaneously by more than one person.
All this work is done locally on the developer’s machine before anything is pushed to a
"contrib" area and examined at the maintainer’s level.
</p><p>
A somewhat formal method exists by which developers commit changes and push them into the
"contrib" area and subsequently request that the maintainer include them into "master"
This process is called “submitting a patch” or “submitting a change.”
</p><p>
To summarize the environment: we have a single point of entry for changes into the project’s
"master" branch of the Git repository, which is controlled by the project’s maintainer.
And, we have a set of developers who independently develop, test, and submit changes
to "contrib" areas for the maintainer to examine.
The maintainer then chooses which changes are going to become a permanent part of the project.
</p><p>
</p><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr style="height: 270px"><td align="left"><img src="figures/git-workflow.png" align="left" height="270" /></td></tr></table><p>
</p><p>
While each development environment is unique, there are some best practices or methods
that help development run smoothly.
The following list describes some of these practices.
For more information about Git workflows, see the workflow topics in the
<a class="ulink" href="http://book.git-scm.com" target="_top">Git Community Book</a>.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Make Small Changes:</em></span> It is best to keep the changes you commit
small as compared to bundling many disparate changes into a single commit.
This practice not only keeps things manageable but also allows the maintainer
to more easily include or refuse changes.</p><p>It is also good practice to leave the repository in a state that allows you to
still successfully build your project. In other words, do not commit half of a feature,
then add the other half in a separate, later commit.
Each commit should take you from one buildable project state to another
buildable state.</p></li><li class="listitem"><p><span class="emphasis"><em>Use Branches Liberally:</em></span> It is very easy to create, use, and
delete local branches in your working Git repository.
You can name these branches anything you like.
It is helpful to give them names associated with the particular feature or change
on which you are working.
Once you are done with a feature or change, simply discard the branch.</p></li><li class="listitem"><p><span class="emphasis"><em>Merge Changes:</em></span> The <code class="filename">git merge</code>
command allows you to take the
changes from one branch and fold them into another branch.
This process is especially helpful when more than a single developer might be working
on different parts of the same feature.
Merging changes also automatically identifies any collisions or “conflicts”
that might happen as a result of the same lines of code being altered by two different
developers.</p></li><li class="listitem"><p><span class="emphasis"><em>Manage Branches:</em></span> Because branches are easy to use, you should
use a system where branches indicate varying levels of code readiness.
For example, you can have a “work” branch to develop in, a “test” branch where the code or
change is tested, a “stage” branch where changes are ready to be committed, and so forth.
As your project develops, you can merge code across the branches to reflect ever-increasing
stable states of the development.</p></li><li class="listitem"><p><span class="emphasis"><em>Use Push and Pull:</em></span> The push-pull workflow is based on the
concept of developers “pushing” local commits to a remote repository, which is
usually a contribution repository.
This workflow is also based on developers “pulling” known states of the project down into their
local development repositories.
The workflow easily allows you to pull changes submitted by other developers from the
upstream repository into your work area ensuring that you have the most recent software
on which to develop.
The Yocto Project has two scripts named <code class="filename">create-pull-request</code> and
<code class="filename">send-pull-request</code> that ship with the release to facilitate this
workflow.
You can find these scripts in the local Yocto Project files Git repository in
the <code class="filename">scripts</code> directory.</p></li><li class="listitem"><p><span class="emphasis"><em>Patch Workflow:</em></span> This workflow allows you to notify the
maintainer through an email that you have a change (or patch) you would like considered
for the "master" branch of the Git repository.
To send this type of change you format the patch and then send the email using the Git commands
<code class="filename">git format-patch</code> and <code class="filename">git send-email</code>.
You can find information on how to submit later in this chapter.</p></li></ul></div><p>
</p></div><div class="section" title="3.8. Tracking Bugs"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="tracking-bugs"></a>3.8. Tracking Bugs</h2></div></div></div><p>
The Yocto Project uses its own implementation of
<a class="ulink" href="http://www.bugzilla.org/about/" target="_top">Bugzilla</a> to track bugs.
Implementations of Bugzilla work well for group development because they track bugs and code
changes, can be used to communicate changes and problems with developers, can be used to
submit and review patches, and can be used to manage quality assurance.
The home page for the Yocto Project implementation of Bugzilla is
<a class="ulink" href="http://bugzilla.yoctoproject.org" target="_top">http://bugzilla.yoctoproject.org</a>.
</p><p>
Sometimes it is helpful to submit, investigate, or track a bug against the Yocto Project itself
such as when discovering an issue with some component of the build system that acts contrary
to the documentation or your expectations.
Following is the general procedure for submitting a new bug using the Yocto Project
Bugzilla.
You can find more information on defect management, bug tracking, and feature request
processes all accomplished through the Yocto Project Bugzilla on the wiki page
<a class="ulink" href="https://wiki.yoctoproject.org/wiki/Bugzilla_Configuration_and_Bug_Tracking" target="_top">here</a>.
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Always use the Yocto Project implementation of Bugzilla to submit
a bug.</p></li><li class="listitem"><p>When submitting a new bug, be sure to choose the appropriate
Classification, Product, and Component for which the issue was found.
Defects for Yocto Project fall into one of four classifications: Yocto Projects,
Infrastructure, Poky, and Yocto Metadata Layers.
Each of these Classifications break down into multiple Products and, in some
cases, multiple Components.</p></li><li class="listitem"><p>Use the bug form to choose the correct Hardware and Architecture
for which the bug applies.</p></li><li class="listitem"><p>Indicate the Yocto Project version you were using when the issue
occurred.</p></li><li class="listitem"><p>Be sure to indicate the Severity of the bug.
Severity communicates how the bug impacted your work.</p></li><li class="listitem"><p>Provide a brief summary of the issue.
Try to limit your summary to just a line or two and be sure to capture the
essence of the issue.</p></li><li class="listitem"><p>Provide a detailed description of the issue.
You should provide as much detail as you can about the context, behavior, output,
and so forth that surround the issue.
You can even attach supporting files for output or log by using the "Add an attachment"
button.</p></li><li class="listitem"><p>Submit the bug by clicking the "Submit Bug" button.</p></li></ol></div><p>
</p></div><div class="section" title="3.9. How to Submit a Change"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="how-to-submit-a-change"></a>3.9. How to Submit a Change</h2></div></div></div><p>
Contributions to the Yocto Project and OpenEmbedded are very welcome.
Because the system is extremely configurable and flexible, we recognize that developers
will want to extend, configure or optimize it for their specific uses.
You should send patches to the appropriate mailing list so that they
can be reviewed and merged by the appropriate maintainer.
For a list of the Yocto Project and related mailing lists, see the
"<a class="link" href="#resources-mailinglist" target="_top">Mailing lists</a>" section in
the Yocto Project Reference Manual.
</p><p>
The following is some guidance on which mailing list to use for what type of change:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>For changes to the core metadata, send your patch to the
<a class="ulink" href="http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/openembedded-core" target="_top">openembedded-core</a> mailing list.
For example, a change to anything under the <code class="filename">meta</code> or
<code class="filename">scripts</code> directories
should be sent to this mailing list.</p></li><li class="listitem"><p>For changes to BitBake (anything under the <code class="filename">bitbake</code>
directory), send your patch to the
<a class="ulink" href="http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/bitbake-devel" target="_top">bitbake-devel</a> mailing list.</p></li><li class="listitem"><p>For changes to <code class="filename">meta-yocto</code>, send your patch to the
<a class="ulink" href="http://lists.yoctoproject.org/listinfo/poky" target="_top">poky</a> mailing list.</p></li><li class="listitem"><p>For changes to other layers hosted on yoctoproject.org (unless the
layer's documentation specifies otherwise), tools, and Yocto Project
documentation, use the
<a class="ulink" href="http://lists.yoctoproject.org/listinfo/yocto" target="_top">yocto</a> mailing list.</p></li><li class="listitem"><p>For additional recipes that do not fit into the core metadata,
you should determine which layer the recipe should go into and submit the
change in the manner recommended by the documentation (e.g. README) supplied
with the layer. If in doubt, please ask on the
<a class="ulink" href="http://lists.yoctoproject.org/listinfo/yocto" target="_top">yocto</a> or
<a class="ulink" href="http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/openembedded-devel" target="_top">openembedded-devel</a>
mailing lists.</p></li></ul></div><p>
</p><p>
When you send a patch, be sure to include a "Signed-off-by:"
line in the same style as required by the Linux kernel.
Adding this line signifies that you, the submitter, have agreed to the Developer's Certificate of Origin 1.1
as follows:
</p><pre class="literallayout">
Developer's Certificate of Origin 1.1
By making a contribution to this project, I certify that:
(a) The contribution was created in whole or in part by me and I
have the right to submit it under the open source license
indicated in the file; or
(b) The contribution is based upon previous work that, to the best
of my knowledge, is covered under an appropriate open source
license and I have the right under that license to submit that
work with modifications, whether created in whole or in part
by me, under the same open source license (unless I am
permitted to submit under a different license), as indicated
in the file; or
(c) The contribution was provided directly to me by some other
person who certified (a), (b) or (c) and I have not modified
it.
(d) I understand and agree that this project and the contribution
are public and that a record of the contribution (including all
personal information I submit with it, including my sign-off) is
maintained indefinitely and may be redistributed consistent with
this project or the open source license(s) involved.
</pre><p>
</p><p>
In a collaborative environment, it is necessary to have some sort of standard
or method through which you submit changes.
Otherwise, things could get quite chaotic.
One general practice to follow is to make small, controlled changes.
Keeping changes small and isolated aids review, makes merging/rebasing easier
and keeps the change history clean when anyone needs to refer to it in future.
</p><p>
When you make a commit, you must follow certain standards established by the
OpenEmbedded and Yocto Project development teams.
For each commit, you must provide a single-line summary of the change and you
should almost always provide a more detailed description of what you did (i.e.
the body of the commit message).
The only exceptions for not providing a detailed description would be if your
change is a simple, self-explanatory change that needs no description.
Here are the guidelines for composing a commit message:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Provide a single-line, short summary of the change.
This summary is typically viewable in the "shortlist" of changes.
Thus, providing something short and descriptive that gives the reader
a summary of the change is useful when viewing a list of many commits.
This should be prefixed by the recipe name (if changing a recipe), or
else the short form path to the file being changed.
</p></li><li class="listitem"><p>For the body of the commit message, provide detailed information
that describes what you changed, why you made the change, and the approach
you used. It may also be helpful if you mention how you tested the change.
Provide as much detail as you can in the body of the commit message.
</p></li><li class="listitem"><p>If the change addresses a specific bug or issue that is
associated with a bug-tracking ID, include a reference to that ID in
your detailed description.
For example, the Yocto Project uses a specific convention for bug
references - any commit that addresses a specific bug should include the
bug ID in the description (typically at the beginning) as follows:
</p><pre class="literallayout">
[YOCTO #&lt;bug-id&gt;]
&lt;detailed description of change&gt;
</pre></li></ul></div><p>
</p><p>
You can find more guidance on creating well-formed commit messages at this OpenEmbedded
wiki page:
<a class="ulink" href="http://www.openembedded.org/wiki/Commit_Patch_Message_Guidelines" target="_top">http://www.openembedded.org/wiki/Commit_Patch_Message_Guidelines</a>.
</p><p>
Following are general instructions for both pushing changes upstream and for submitting
changes as patches.
</p><div class="section" title="3.9.1. Using Scripts to Push a Change Upstream and Request a Pull"><div class="titlepage"><div><div><h3 class="title"><a id="pushing-a-change-upstream"></a>3.9.1. Using Scripts to Push a Change Upstream and Request a Pull</h3></div></div></div><p>
The basic flow for pushing a change to an upstream "contrib" Git repository is as follows:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Make your changes in your local Git repository.</p></li><li class="listitem"><p>Stage your changes by using the <code class="filename">git add</code>
command on each file you changed.</p></li><li class="listitem"><p>Commit the change by using the <code class="filename">git commit</code>
command and push it to the "contrib" repository.
Be sure to provide a commit message that follows the project’s commit message standards
as described earlier.</p></li><li class="listitem"><p>Notify the maintainer that you have pushed a change by making a pull
request.
The Yocto Project provides two scripts that conveniently let you generate and send
pull requests to the Yocto Project.
These scripts are <code class="filename">create-pull-request</code> and
<code class="filename">send-pull-request</code>.
You can find these scripts in the <code class="filename">scripts</code> directory of the
Yocto Project file structure.</p><p>Using these scripts correctly formats the requests without introducing any
whitespace or HTML formatting.
The maintainer that receives your patches needs to be able to save and apply them
directly from your emails.
Using these scripts is the preferred method for sending patches.</p><p>For help on using these scripts, simply provide the
<code class="filename">-h</code> argument as follows:
</p><pre class="literallayout">
$ ~/poky/scripts/create-pull-request -h
$ ~/poky/scripts/send-pull-request -h
</pre></li></ul></div><p>
</p><p>
You can find general Git information on how to push a change upstream in the
<a class="ulink" href="http://book.git-scm.com/3_distributed_workflows.html" target="_top">Git Community Book</a>.
</p></div><div class="section" title="3.9.2. Using Email to Submit a Patch"><div class="titlepage"><div><div><h3 class="title"><a id="submitting-a-patch"></a>3.9.2. Using Email to Submit a Patch</h3></div></div></div><p>
You can submit patches without using the <code class="filename">create-pull-request</code> and
<code class="filename">send-pull-request</code> scripts described in the previous section.
Keep in mind, the preferred method is to use the scripts, however.
</p><p>
Depending on the components changed, you need to submit the email to a specific
mailing list.
For some guidance on which mailing list to use, see the list in the
"<a class="link" href="#how-to-submit-a-change" title="3.9. How to Submit a Change">How to Submit a Change</a>" section
earlier in this manual.
For a description of the available mailing lists, see
"<a class="link" href="#resources-mailinglist" target="_top">Mailing Lists</a>"
section in the Yocto Project Reference Manual.
</p><p>
Here is the general procedure on how to submit a patch through email without using the
scripts:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Make your changes in your local Git repository.</p></li><li class="listitem"><p>Stage your changes by using the <code class="filename">git add</code>
command on each file you changed.</p></li><li class="listitem"><p>Commit the change by using the
<code class="filename">git commit --signoff</code> command.
Using the <code class="filename">--signoff</code> option identifies you as the person
making the change and also satisfies the Developer's Certificate of
Origin (DCO) shown earlier.</p><p>When you form a commit you must follow certain standards established by the
Yocto Project development team.
See the earlier section
"<a class="link" href="#how-to-submit-a-change" title="3.9. How to Submit a Change">How to Submit a Change</a>"
for Yocto Project commit message standards.</p></li><li class="listitem"><p>Format the commit into an email message.
To format commits, use the <code class="filename">git format-patch</code> command.
When you provide the command, you must include a revision list or a number of patches
as part of the command.
For example, these two commands each take the most recent single commit and
format it as an email message in the current directory:
</p><pre class="literallayout">
$ git format-patch -1
$ git format-patch HEAD~
</pre><p>After the command is run, the current directory contains a
numbered <code class="filename">.patch</code> file for the commit.</p><p>If you provide several commits as part of the command,
the <code class="filename">git format-patch</code> command produces a numbered
series of files in the current directory – one for each commit.
If you have more than one patch, you should also use the
<code class="filename">--cover</code> option with the command, which generates a
cover letter as the first "patch" in the series.
You can then edit the cover letter to provide a description for
the series of patches.
For information on the <code class="filename">git format-patch</code> command,
see <code class="filename">GIT_FORMAT_PATCH(1)</code> displayed using the
<code class="filename">man git-format-patch</code> command.</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>If you are or will be a frequent contributor to the Yocto Project
or to OpenEmbedded, you might consider requesting a contrib area and the
necessary associated rights.</div></li><li class="listitem"><p>Import the files into your mail client by using the
<code class="filename">git send-email</code> command.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>In order to use <code class="filename">git send-email</code>, you must have the
the proper Git packages installed.
For Ubuntu and Fedora the package is <code class="filename">git-email</code>.</div><p>The <code class="filename">git send-email</code> command sends email by using a local
or remote Mail Transport Agent (MTA) such as
<code class="filename">msmtp</code>, <code class="filename">sendmail</code>, or through a direct
<code class="filename">smtp</code> configuration in your Git <code class="filename">config</code>
file.
If you are submitting patches through email only, it is very important
that you submit them without any whitespace or HTML formatting that
either you or your mailer introduces.
The maintainer that receives your patches needs to be able to save and
apply them directly from your emails.
A good way to verify that what you are sending will be applicable by the
maintainer is to do a dry run and send them to yourself and then
save and apply them as the maintainer would.</p><p>The <code class="filename">git send-email</code> command is the preferred method
for sending your patches since there is no risk of compromising whitespace
in the body of the message, which can occur when you use your own mail client.
The command also has several options that let you
specify recipients and perform further editing of the email message.
For information on how to use the <code class="filename">git send-email</code> command,
use the <code class="filename">man git-send-email</code> command.</p></li></ul></div><p>
</p></div></div></div>
<div class="chapter" title="Chapter 4. Common Tasks"><div class="titlepage"><div><div><h2 class="title"><a id="extendpoky"></a>Chapter 4. Common Tasks</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#understanding-and-creating-layers">4.1. Understanding and Creating Layers</a></span></dt><dd><dl><dt><span class="section"><a href="#yocto-project-layers">4.1.1. Layers</a></span></dt><dt><span class="section"><a href="#creating-your-own-layer">4.1.2. Creating Your Own Layer</a></span></dt><dt><span class="section"><a href="#enabling-your-layer">4.1.3. Enabling Your Layer</a></span></dt><dt><span class="section"><a href="#using-bbappend-files">4.1.4. Using .bbappend Files</a></span></dt><dt><span class="section"><a href="#prioritizing-your-layer">4.1.5. Prioritizing Your Layer</a></span></dt><dt><span class="section"><a href="#managing-layers">4.1.6. Managing Layers</a></span></dt></dl></dd><dt><span class="section"><a href="#usingpoky-extend-customimage">4.2. Customizing Images</a></span></dt><dd><dl><dt><span class="section"><a href="#usingpoky-extend-customimage-custombb">4.2.1. Customizing Images Using Custom .bb Files</a></span></dt><dt><span class="section"><a href="#usingpoky-extend-customimage-customtasks">4.2.2. Customizing Images Using Custom Tasks</a></span></dt><dt><span class="section"><a href="#usingpoky-extend-customimage-imagefeatures">4.2.3. Customizing Images Using Custom <code class="filename">IMAGE_FEATURES</code> and
<code class="filename">EXTRA_IMAGE_FEATURES</code></a></span></dt><dt><span class="section"><a href="#usingpoky-extend-customimage-localconf">4.2.4. Customizing Images Using <code class="filename">local.conf</code></a></span></dt></dl></dd><dt><span class="section"><a href="#usingpoky-extend-addpkg">4.3. Adding a Package</a></span></dt><dd><dl><dt><span class="section"><a href="#usingpoky-extend-addpkg-singlec">4.3.1. Single .c File Package (Hello World!)</a></span></dt><dt><span class="section"><a href="#usingpoky-extend-addpkg-autotools">4.3.2. Autotooled Package</a></span></dt><dt><span class="section"><a href="#usingpoky-extend-addpkg-makefile">4.3.3. Makefile-Based Package</a></span></dt><dt><span class="section"><a href="#splitting-an-application-into-multiple-packages">4.3.4. Splitting an Application into Multiple Packages</a></span></dt><dt><span class="section"><a href="#including-static-library-files">4.3.5. Including Static Library Files</a></span></dt><dt><span class="section"><a href="#usingpoky-extend-addpkg-postinstalls">4.3.6. Post Install Scripts</a></span></dt></dl></dd><dt><span class="section"><a href="#platdev-newmachine">4.4. Adding a New Machine</a></span></dt><dd><dl><dt><span class="section"><a href="#platdev-newmachine-conffile">4.4.1. Adding the Machine Configuration File</a></span></dt><dt><span class="section"><a href="#platdev-newmachine-kernel">4.4.2. Adding a Kernel for the Machine</a></span></dt><dt><span class="section"><a href="#platdev-newmachine-formfactor">4.4.3. Adding a Formfactor Configuration File</a></span></dt></dl></dd><dt><span class="section"><a href="#building-multiple-architecture-libraries-into-one-image">4.5. Combining Multiple Versions of Library Files into One Image</a></span></dt><dd><dl><dt><span class="section"><a href="#preparing-to-use-multilib">4.5.1. Preparing to use Multilib</a></span></dt><dt><span class="section"><a href="#using-multilib">4.5.2. Using Multilib</a></span></dt><dt><span class="section"><a href="#additional-implementation-details">4.5.3. Additional Implementation Details</a></span></dt></dl></dd><dt><span class="section"><a href="#configuring-the-kernel">4.6. Configuring the Kernel</a></span></dt><dd><dl><dt><span class="section"><a href="#using-menuconfig">4.6.1. Using  <code class="filename">menuconfig</code></a></span></dt><dt><span class="section"><a href="#creating-config-fragments">4.6.2. Creating Configuration Fragments</a></span></dt><dt><span class="section"><a href="#fine-tuning-the-kernel-configuration-file">4.6.3. Fine-tuning the Kernel Configuration File</a></span></dt></dl></dd><dt><span class="section"><a href="#usingpoky-changes-updatingimages">4.7. Updating Existing Images</a></span></dt><dt><span class="section"><a href="#usingpoky-changes-prbump">4.8. Incrementing a Package Revision Number</a></span></dt><dt><span class="section"><a href="#usingpoky-configuring-DISTRO_PN_ALIAS">4.9. Handling a Package Name Alias</a></span></dt><dt><span class="section"><a href="#building-software-from-an-external-source">4.10. Building Software from an External Source</a></span></dt><dt><span class="section"><a href="#excluding-recipes-from-the-build">4.11. Excluding Recipes From the Build</a></span></dt><dt><span class="section"><a href="#platdev-appdev-srcrev">4.12. Using an External SCM</a></span></dt><dt><span class="section"><a href="#platdev-gdb-remotedebug">4.13. Debugging With the GNU Project Debugger (GDB) Remotely</a></span></dt><dd><dl><dt><span class="section"><a href="#platdev-gdb-remotedebug-launch-gdbserver">4.13.1. Launching Gdbserver on the Target</a></span></dt><dt><span class="section"><a href="#platdev-gdb-remotedebug-launch-gdb">4.13.2. Launching GDB on the Host Computer</a></span></dt></dl></dd><dt><span class="section"><a href="#platdev-oprofile">4.14. Profiling with OProfile</a></span></dt><dd><dl><dt><span class="section"><a href="#platdev-oprofile-target">4.14.1. Profiling on the Target</a></span></dt><dt><span class="section"><a href="#platdev-oprofile-oprofileui">4.14.2. Using OProfileUI</a></span></dt></dl></dd></dl></div><p>
This chapter describes standard tasks such as adding new
software packages, extending or customizing images, and porting work to
new hardware (adding a new machine).
The chapter also describes how to combine multiple
versions of library files into a single image, how to handle a package name alias, and
gives advice about how to make changes to the Yocto Project to achieve the best results.
</p><div class="section" title="4.1. Understanding and Creating Layers"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="understanding-and-creating-layers"></a>4.1. Understanding and Creating Layers</h2></div></div></div><p>
The OpenEmbedded build system supports organizing <a class="link" href="#metadata">metadata</a>
into multiple layers.
Layers allow you to isolate different types of customizations from each other.
You might find it tempting to keep everything in one layer when working on a single project.
However, the more modular you organize your metadata, the easier it is to cope with future changes.
</p><p>
To illustrate how layers are used to keep things modular, consider machine customizations.
These types of customizations typically reside in a BSP Layer.
Furthermore, the machine customizations should be isolated from recipes and metadata that support
a new GUI environment, for example.
This situation gives you a couple a layers: one for the machine configurations, and one for the
GUI environment.
It is important to understand, however, that the BSP layer can still make machine-specific
additions to recipes within the GUI environment layer without polluting the GUI layer itself
with those machine-specific changes.
You can accomplish this through a recipe that is a BitBake append
(<code class="filename">.bbappend</code>) file, which is described later in this section.
</p><p>
</p><div class="section" title="4.1.1. Layers"><div class="titlepage"><div><div><h3 class="title"><a id="yocto-project-layers"></a>4.1.1. Layers</h3></div></div></div><p>
The source directory contains several layers right out of the box.
You can easily identify a layer in the source directory by its folder name.
Folders that are layers begin with the string <code class="filename">meta</code>.
For example, when you set up the <a class="link" href="#source-directory">source directory</a>
structure, you will see several layers: <code class="filename">meta</code>, <code class="filename">meta-demoapps</code>,
<code class="filename">meta-skeleton</code>, and <code class="filename">meta-yocto</code>.
Each of these folders is a layer.
</p><p>
Furthermore, if you set up a local copy of the <code class="filename">meta-intel</code> Git repository
and then explore that folder, you will discover many BSP layers within the
<code class="filename">meta-intel</code> layer.
For more information on BSP layers, see the
"<a class="link" href="#bsp-layers" target="_top">BSP Layers</a>"
section in the Yocto Project Board Support Package (BSP) Developer's Guide.
</p></div><div class="section" title="4.1.2. Creating Your Own Layer"><div class="titlepage"><div><div><h3 class="title"><a id="creating-your-own-layer"></a>4.1.2. Creating Your Own Layer</h3></div></div></div><p>
It is very easy to create your own layer to use with the OpenEmbedded build system.
Follow these general steps to create your layer:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p><span class="emphasis"><em>Check Existing Layers:</em></span> Before creating a new layer,
you should be sure someone has not already created a layer containing the metadata
you need.
You can see the
<a class="ulink" href="http://www.openembedded.org/wiki/LayerIndex" target="_top"><code class="filename">LayerIndex</code></a>
for a list of layers from the OpenEmbedded community that can be used in the
Yocto Project.</p></li><li class="listitem"><p><span class="emphasis"><em>Create a Directory:</em></span> Create the directory
for your layer.
Traditionally, prepend the name of the folder with the string
<code class="filename">meta</code>.
For example:
</p><pre class="literallayout">
meta-mylayer
meta-GUI_xyz
meta-mymachine
</pre></li><li class="listitem"><p><span class="emphasis"><em>Create a Layer Configuration File:</em></span> Inside your new
layer folder, you need to create a <code class="filename">conf/layer.conf</code> file.
It is easiest to take an existing layer configuration file and copy that to your
layer's <code class="filename">conf</code> directory and then modify the file as needed.</p><p>The <code class="filename">meta-yocto/conf/layer.conf</code> file demonstrates the
required syntax:
</p><pre class="literallayout">
# We have a conf and classes directory, add to BBPATH
BBPATH := "${LAYERDIR}:${BBPATH}"
# We have recipes-* directories, add to BBFILES
BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb \
${LAYERDIR}/recipes-*/*/*.bbappend"
BBFILE_COLLECTIONS += "yocto"
BBFILE_PATTERN_yocto := "^${LAYERDIR}/"
BBFILE_PRIORITY_yocto = "5"
</pre><p>In the previous example, the recipes for the layers are added to
<code class="filename"><a class="link" href="#var-BBFILES" target="_top">BBFILES</a></code>.
The
<code class="filename"><a class="link" href="#var-BBFILE_COLLECTIONS" target="_top">BBFILE_COLLECTIONS</a></code>
variable is then appended with the layer name.
The
<code class="filename"><a class="link" href="#var-BBFILE_PATTERN" target="_top">BBFILE_PATTERN</a></code>
variable is set to a regular expression and is used to match files
from <code class="filename">BBFILES</code> into a particular layer.
In this case, immediate expansion of
<code class="filename"><a class="link" href="#var-LAYERDIR" target="_top">LAYERDIR</a></code>
sets <code class="filename">BBFILE_PATTERN</code> to the layer's path.
The
<code class="filename"><a class="link" href="#var-BBFILE_PRIORITY" target="_top">BBFILE_PRIORITY</a></code>
variable then assigns a priority to the layer.
Applying priorities is useful in situations where the same package might appear in multiple
layers and allows you to choose what layer should take precedence.</p><p>Note the use of the
<code class="filename"><a class="link" href="#var-LAYERDIR" target="_top">LAYERDIR</a></code>
variable with the immediate expansion operator.
The <code class="filename">LAYERDIR</code> variable expands to the directory of the current layer and
requires the immediate expansion operator so that BitBake does not wait to expand the variable
when it's parsing a different directory.</p><p>Through the use of the <code class="filename">BBPATH</code> variable,
BitBake locates <code class="filename">.bbclass</code> files, configuration
files, and files that are included with <code class="filename">include</code>
and <code class="filename">require</code> statements.
For these cases, BitBake uses the first file with the matching name found in
<code class="filename">BBPATH</code>.
This is similar to the way the <code class="filename">PATH</code> variable is used for binaries.
We recommend, therefore, that you use unique <code class="filename">.bbclass</code>
and configuration file names in your custom layer.</p></li><li class="listitem"><p><span class="emphasis"><em>Add Content:</em></span> Depending on the type of layer,
add the content.
If the layer adds support for a machine, add the machine configuration in
a <code class="filename">conf/machine/</code> file within the layer.
If the layer adds distro policy, add the distro configuration in a
<code class="filename">conf/distro/</code> file with the layer.
If the layer introduces new recipes, put the recipes you need in
<code class="filename">recipes-*</code> subdirectories within the layer.</p></li></ol></div><p>
</p><p>
To create layers that are easier to maintain, you should consider the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Avoid "overlaying" entire recipes from other layers in your
configuration.
In other words, don't copy an entire recipe into your layer and then modify it.
Use <code class="filename">.bbappend</code> files to override the parts of the
recipe you need to modify.</p></li><li class="listitem"><p>Avoid duplicating include files.
Use <code class="filename">.bbappend</code> files for each recipe that uses an include
file.
Or, if you are introducing a new recipe that requires the included file, use the
path relative to the original layer directory to refer to the file.
For example, use <code class="filename">require recipes-core/somepackage/somefile.inc</code>
instead of <code class="filename">require somefile.inc</code>.
If you're finding you have to overlay the include file, it could indicate a
deficiency in the include file in the layer to which it originally belongs.
If this is the case, you need to address that deficiency instead of overlaying
the include file.
For example, consider how Qt 4 database support plugins are configured.
The source directory does not have
MySQL or PostgreSQL, however OpenEmbedded's
layer <code class="filename">meta-oe</code> does.
Consequently, <code class="filename">meta-oe</code> uses <code class="filename">.bbappend</code>
files to modify the <code class="filename">QT_SQL_DRIVER_FLAGS</code> variable to enable
the appropriate plugins.
This variable was added to the <code class="filename">qt4.inc</code> include file in
the source directory specifically to allow the <code class="filename">meta-oe</code> layer
to be able to control which plugins are built.</p></li></ul></div><p>
</p><p>
We also recommend the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Store custom layers in a Git repository that uses the
<code class="filename">meta-&lt;layer_name&gt;</code> format.</p></li><li class="listitem"><p>Clone the repository alongside other <code class="filename">meta</code>
directories in the
<a class="link" href="#source-directory">source directory</a>.</p></li></ul></div><p>
Following these recommendations keeps your source directory and
its configuration entirely inside the Yocto Project's core base.
</p></div><div class="section" title="4.1.3. Enabling Your Layer"><div class="titlepage"><div><div><h3 class="title"><a id="enabling-your-layer"></a>4.1.3. Enabling Your Layer</h3></div></div></div><p>
Before the OpenEmbedded build system can use your new layer, you need to enable it.
To enable your layer, simply add your layer's path to the
<code class="filename"><a class="link" href="#var-BBLAYERS" target="_top">BBLAYERS</a></code>
variable in your <code class="filename">conf/bblayers.conf</code> file, which is found in the
<a class="link" href="#build-directory">build directory</a>.
The following example shows how to enable a layer named <code class="filename">meta-mylayer</code>:
</p><pre class="literallayout">
LCONF_VERSION = "1"
BBFILES ?= ""
BBLAYERS = " \
/path/to/poky/meta \
/path/to/poky/meta-yocto \
/path/to/poky/meta-mylayer \
"
</pre><p>
</p><p>
BitBake parses each <code class="filename">conf/layer.conf</code> file as specified in the
<code class="filename">BBLAYERS</code> variable within the <code class="filename">conf/bblayers.conf</code>
file.
During the processing of each <code class="filename">conf/layer.conf</code> file, BitBake adds the
recipes, classes and configurations contained within the particular layer to the source
directory.
</p></div><div class="section" title="4.1.4. Using .bbappend Files"><div class="titlepage"><div><div><h3 class="title"><a id="using-bbappend-files"></a>4.1.4. Using .bbappend Files</h3></div></div></div><p>
Recipes used to append metadata to other recipes are called BitBake append files.
BitBake append files use the <code class="filename">.bbappend</code> file type suffix, while
underlying recipes to which metadata is being appended use the
<code class="filename">.bb</code> file type suffix.
</p><p>
A <code class="filename">.bbappend</code> file allows your layer to make additions or
changes to the content of another layer's recipe without having to copy the other
recipe into your layer.
Your <code class="filename">.bbappend</code> file resides in your layer, while the underlying
<code class="filename">.bb</code> recipe file to which you are appending metadata
resides in a different layer.
</p><p>
Append files files must have the same name as the underlying recipe.
For example, the append file <code class="filename">someapp_1.3.bbappend</code> must
apply to <code class="filename">someapp_1.3.bb</code>.
This means the original recipe and append file names are version number specific.
If the underlying recipe is renamed to update to a newer version, the
corresponding <code class="filename">.bbappend</code> file must be renamed as well.
During the build process, BitBake displays an error on starting if it detects a
<code class="filename">.bbappend</code> file that does not have an underlying recipe
with a matching name.
</p><p>
Being able to append information to an existing recipe not only avoids duplication,
but also automatically applies recipe changes in a different layer to your layer.
If you were copying recipes, you would have to manually merge changes as they occur.
</p><p>
As an example, consider the main formfactor recipe and a corresponding formfactor
append file both from the
<a class="link" href="#source-directory">source directory</a>.
Here is the main formfactor recipe, which is named <code class="filename">formfactor_0.0.bb</code> and
located in the meta layer at <code class="filename">meta/recipes-bsp/formfactor</code>:
</p><pre class="literallayout">
DESCRIPTION = "Device formfactor information"
SECTION = "base"
LICENSE = "MIT"
LIC_FILES_CHKSUM = "file://${COREBASE}/LICENSE;md5=3f40d7994397109285ec7b81fdeb3b58 \
file://${COREBASE}/meta/COPYING.MIT;md5=3da9cfbcb788c80a0384361b4de20420"
PR = "r20"
SRC_URI = "file://config file://machconfig"
S = "${WORKDIR}"
PACKAGE_ARCH = "${MACHINE_ARCH}"
INHIBIT_DEFAULT_DEPS = "1"
do_install() {
# Only install file if it has a contents
install -d ${D}${sysconfdir}/formfactor/
install -m 0644 ${S}/config ${D}${sysconfdir}/formfactor/
if [ -s "${S}/machconfig" ]; then
install -m 0644 ${S}/machconfig ${D}${sysconfdir}/formfactor/
fi
}
</pre><p>
Here is the append file, which is named <code class="filename">formfactor_0.0.bbappend</code> and is from the
Crown Bay BSP Layer named <code class="filename">meta-intel/meta-crownbay</code>.
The file is in <code class="filename">recipes-bsp/formfactor</code>:
</p><pre class="literallayout">
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
PRINC = "1"
</pre><p>
This example adds or overrides files in
<a class="link" href="#var-SRC_URI" target="_top"><code class="filename">SRC_URI</code></a>
within a <code class="filename">.bbappend</code> by extending the path BitBake uses to search for files.
The most reliable way to do this is by prepending the
<code class="filename">FILESEXTRAPATHS</code> variable.
For example, if you have your files in a directory that is named the same as your package
(<a class="link" href="#var-PN" target="_top"><code class="filename">PN</code></a>),
you can add this directory by adding the following to your <code class="filename">.bbappend</code> file:
</p><pre class="literallayout">
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
</pre><p>
Using the immediate expansion assignment operator <code class="filename">:=</code> is important because
of the reference to <code class="filename">THISDIR</code>.
The trailing colon character is important as it ensures that items in the list remain
colon-separated.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>BitBake automatically defines the <code class="filename">THISDIR</code> variable.
You should never set this variable yourself.
Using <code class="filename">_prepend</code> ensures your path will be searched prior to other
paths in the final list.
</div><p>
</p><p>
For another example on how to use a <code class="filename">.bbappend</code> file, see the
"<a class="link" href="#changing-recipes-kernel" title="A.5.2.4. Changing  recipes-kernel">Changing <code class="filename">recipes-kernel</code></a>"
section.
</p></div><div class="section" title="4.1.5. Prioritizing Your Layer"><div class="titlepage"><div><div><h3 class="title"><a id="prioritizing-your-layer"></a>4.1.5. Prioritizing Your Layer</h3></div></div></div><p>
Each layer is assigned a priority value.
Priority values control which layer takes precedence if there are recipe files with
the same name in multiple layers.
For these cases, the recipe file from the layer with a higher priority number taking precedence.
Priority values also affect the order in which multiple <code class="filename">.bbappend</code> files
for the same recipe are applied.
You can either specify the priority manually, or allow the build system to calculate it
based on the layer's dependencies.
</p><p>
To specify the layer's priority manually, use the
<a class="link" href="#var-BBFILE_PRIORITY" target="_top"><code class="filename">BBFILE_PRIORITY</code></a>
variable.
For example:
</p><pre class="literallayout">
BBFILE_PRIORITY := "1"
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>It is possible for a recipe with a lower version number
<a class="link" href="#var-PV" target="_top"><code class="filename">PV</code></a>
in a layer that has a higher priority to take precedence.</p><p>Also, the layer priority does not currently affect the precedence order of
<code class="filename">.conf</code> or <code class="filename">.bbclass</code> files.
Future versions of BitBake might address this.</p></div></div><div class="section" title="4.1.6. Managing Layers"><div class="titlepage"><div><div><h3 class="title"><a id="managing-layers"></a>4.1.6. Managing Layers</h3></div></div></div><p>
You can use the BitBake layer management tool to provide a view into the structure of
recipes across a multi-layer project.
Being able to generate output that reports on configured layers with their paths and
priorities and on <code class="filename">.bbappend</code> files and their applicable recipes
can help to reveal potential problems.
</p><p>
Use the following form when running the layer management tool.
</p><pre class="literallayout">
$ bitbake-layers &lt;command&gt; [arguments]
</pre><p>
The following list describes the available commands:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><span class="emphasis"><em>help:</em></span></code>
Displays general help or help on a specified command.</p></li><li class="listitem"><p><code class="filename"><span class="emphasis"><em>show-layers:</em></span></code>
Show the current configured layers.</p></li><li class="listitem"><p><code class="filename"><span class="emphasis"><em>show-recipes:</em></span></code>
Lists available recipes and the layers that provide them.
</p></li><li class="listitem"><p><code class="filename"><span class="emphasis"><em>show-overlayed:</em></span></code>
Lists overlayed recipes.
A recipe is overlayed when a recipe with the same name exists in another layer
that has a higher layer priority.
</p></li><li class="listitem"><p><code class="filename"><span class="emphasis"><em>show-appends:</em></span></code>
Lists <code class="filename">.bbappend</code> files and the recipe files to which
they apply.</p></li><li class="listitem"><p><code class="filename"><span class="emphasis"><em>flatten:</em></span></code>
Flattens the layer configuration into a separate output directory.
Flattening your layer configuration builds a "flattened" directory that contains
the contents of all layers, with any overlayed recipes removed and any
<code class="filename">.bbappend</code> files appended to the corresponding recipes.
You might have to perform some manual cleanup of the flattened layer as follows:
</p><div class="itemizedlist"><ul class="itemizedlist" type="circle"><li class="listitem"><p>Non-recipe files (such as patches) are overwritten.
The flatten command shows a warning for these files.</p></li><li class="listitem"><p>Anything beyond the normal layer setup has been added to
the <code class="filename">layer.conf</code> file.
Only the lowest priority layer's <code class="filename">layer.conf</code> is used.
</p></li><li class="listitem"><p>Overridden and appended items from <code class="filename">.bbappend</code>
files need to be cleaned up.
The contents of each <code class="filename">.bbappend</code> end up in the
flattened recipe.
However, if there are appended or changed variable values, you need to tidy
these up yourself.
Consider the following example.
Here, the <code class="filename">bitbake-layers</code> command adds the line
<code class="filename">#### bbappended ...</code> so that you know where the following
lines originate:
</p><pre class="literallayout">
...
DESCRIPTION = "A useful utility"
...
EXTRA_OECONF = "--enable-something"
...
#### bbappended from meta-anotherlayer ####
DESCRIPTION = "Customized utility"
EXTRA_OECONF += "--enable-somethingelse"
</pre><p>
Ideally, you would tidy up these utilities as follows:
</p><pre class="literallayout">
...
DESCRIPTION = "Customized utility"
...
EXTRA_OECONF = "--enable-something --enable-somethingelse"
...
</pre></li></ul></div></li></ul></div><p>
</p></div></div><div class="section" title="4.2. Customizing Images"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="usingpoky-extend-customimage"></a>4.2. Customizing Images</h2></div></div></div><p>
You can customize images to satisfy particular requirements.
This section describes several methods and provides guidelines for each.
</p><div class="section" title="4.2.1. Customizing Images Using Custom .bb Files"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-extend-customimage-custombb"></a>4.2.1. Customizing Images Using Custom .bb Files</h3></div></div></div><p>
One way to get additional software into an image is to create a custom image.
The following example shows the form for the two lines you need:
</p><pre class="literallayout">
IMAGE_INSTALL = "task-core-x11-base package1 package2"
inherit core-image
</pre><p>
</p><p>
By creating a custom image, a developer has total control
over the contents of the image.
It is important to use the correct names of packages in the
<code class="filename"><a class="link" href="#var-IMAGE_INSTALL" target="_top">IMAGE_INSTALL</a></code>
variable.
You must use the OpenEmbedded notation and not the Debian notation for the names
(e.g. <code class="filename">eglibc-dev</code> instead of <code class="filename">libc6-dev</code>).
</p><p>
The other method for creating a custom image is to base it on an existing image.
For example, if you want to create an image based on <code class="filename">core-image-sato</code>
but add the additional package <code class="filename">strace</code> to the image,
copy the <code class="filename">meta/recipes-sato/images/core-image-sato.bb</code> to a
new <code class="filename">.bb</code> and add the following line to the end of the copy:
</p><pre class="literallayout">
IMAGE_INSTALL += "strace"
</pre><p>
</p></div><div class="section" title="4.2.2. Customizing Images Using Custom Tasks"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-extend-customimage-customtasks"></a>4.2.2. Customizing Images Using Custom Tasks</h3></div></div></div><p>
For complex custom images, the best approach is to create a custom task package
that is used to build the image or images.
A good example of a tasks package is
<code class="filename">meta/recipes-core/tasks/task-core-boot.bb</code>
The
<code class="filename"><a class="link" href="#var-PACKAGES" target="_top">PACKAGES</a></code>
variable lists the task packages to build along with the complementary
<code class="filename">-dbg</code> and <code class="filename">-dev</code> packages.
For each package added, you can use
<code class="filename"><a class="link" href="#var-RDEPENDS" target="_top">RDEPENDS</a></code>
and
<code class="filename"><a class="link" href="#var-RRECOMMENDS" target="_top">RRECOMMENDS</a></code>
entries to provide a list of packages the parent task package should contain.
Following is an example:
</p><pre class="literallayout">
DESCRIPTION = "My Custom Tasks"
PACKAGES = "\
task-custom-apps \
task-custom-apps-dbg \
task-custom-apps-dev \
task-custom-tools \
task-custom-tools-dbg \
task-custom-tools-dev \
"
RDEPENDS_task-custom-apps = "\
dropbear \
portmap \
psplash"
RDEPENDS_task-custom-tools = "\
oprofile \
oprofileui-server \
lttng-control \
lttng-viewer"
RRECOMMENDS_task-custom-tools = "\
kernel-module-oprofile"
</pre><p>
</p><p>
In the previous example, two task packages are created with their dependencies and their
recommended package dependencies listed: <code class="filename">task-custom-apps</code>, and
<code class="filename">task-custom-tools</code>.
To build an image using these task packages, you need to add
<code class="filename">task-custom-apps</code> and/or
<code class="filename">task-custom-tools</code> to
<code class="filename"><a class="link" href="#var-IMAGE_INSTALL" target="_top">IMAGE_INSTALL</a></code>.
For other forms of image dependencies see the other areas of this section.
</p></div><div class="section" title="4.2.3. Customizing Images Using Custom IMAGE_FEATURES and EXTRA_IMAGE_FEATURES"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-extend-customimage-imagefeatures"></a>4.2.3. Customizing Images Using Custom <code class="filename">IMAGE_FEATURES</code> and
<code class="filename">EXTRA_IMAGE_FEATURES</code></h3></div></div></div><p>
Ultimately users might want to add extra image features to the set by using the
<code class="filename"><a class="link" href="#var-IMAGE_FEATURES" target="_top">IMAGE_FEATURES</a></code>
variable.
To create these features, the best reference is
<code class="filename">meta/classes/core-image.bbclass</code>, which shows how to achieve this.
In summary, the file looks at the contents of the
<code class="filename">IMAGE_FEATURES</code>
variable and then maps that into a set of tasks or packages.
Based on this information the
<code class="filename"><a class="link" href="#var-IMAGE_INSTALL" target="_top"> IMAGE_INSTALL</a></code>
variable is generated automatically.
Users can add extra features by extending the class or creating a custom class for use
with specialized image <code class="filename">.bb</code> files.
You can also add more features by configuring the
<code class="filename"><a class="link" href="#var-EXTRA_IMAGE_FEATURES" target="_top">EXTRA_IMAGE_FEATURES</a></code>
variable in the <code class="filename">local.conf</code> file found in the source directory
located in the build directory.
</p><p>
The Yocto Project ships with two SSH servers you can use in your images:
Dropbear and OpenSSH.
Dropbear is a minimal SSH server appropriate for resource-constrained environments,
while OpenSSH is a well-known standard SSH server implementation.
By default, the <code class="filename">core-image-sato</code> image is configured to use Dropbear.
The <code class="filename">core-image-basic</code> and <code class="filename">core-image-lsb</code>
images both include OpenSSH.
The <code class="filename">core-image-minimal</code> image does not contain an SSH server.
To change these defaults, edit the <code class="filename">IMAGE_FEATURES</code> variable
so that it sets the image you are working with to include
<code class="filename">ssh-server-dropbear</code> or <code class="filename">ssh-server-openssh</code>.
</p></div><div class="section" title="4.2.4. Customizing Images Using local.conf"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-extend-customimage-localconf"></a>4.2.4. Customizing Images Using <code class="filename">local.conf</code></h3></div></div></div><p>
It is possible to customize image contents by using variables from your
local configuration in your <code class="filename">conf/local.conf</code> file.
Because it is limited to local use, this method generally only allows you to
add packages and is not as flexible as creating your own customized image.
When you add packages using local variables this way, you need to realize that
these variable changes affect all images at the same time and might not be
what you require.
</p><p>
The simplest way to add extra packages to all images is by using the
<code class="filename"><a class="link" href="#var-IMAGE_INSTALL" target="_top">IMAGE_INSTALL</a></code>
variable with the <code class="filename">_append</code> operator:
</p><pre class="literallayout">
IMAGE_INSTALL_append = " strace"
</pre><p>
Use of the syntax is important.
Specifically, the space between the quote and the package name, which is
<code class="filename">strace</code> in this example.
This space is required since the <code class="filename">_append</code>
operator does not add the space.
</p><p>
Furthermore, you must use <code class="filename">_append</code> instead of the <code class="filename">+=</code>
operator if you want to avoid ordering issues.
The reason for this is because doing so unconditionally appends to the variable and
avoids ordering problems due to the variable being set in image recipes and
<code class="filename">.bbclass</code> files with operators like <code class="filename">?=</code>.
Using <code class="filename">_append</code> ensures the operation takes affect.
</p><p>
As shown in its simplest use, <code class="filename">IMAGE_INSTALL_append</code> affects
all images.
It is possible to extend the syntax so that the variable applies to a specific image only.
Here is an example:
</p><pre class="literallayout">
IMAGE_INSTALL_append_pn-core-image-minimal = " strace"
</pre><p>
This example adds <code class="filename">strace</code> to <code class="filename">core-image-minimal</code>
only.
</p><p>
You can add packages using a similar approach through the
<code class="filename"><a class="link" href="#var-CORE_IMAGE_EXTRA_INSTALL" target="_top">CORE_IMAGE_EXTRA_INSTALL</a></code>
variable.
If you use this variable, only <code class="filename">core-image-*</code> images are affected.
</p></div></div><div class="section" title="4.3. Adding a Package"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="usingpoky-extend-addpkg"></a>4.3. Adding a Package</h2></div></div></div><p>
To add a package you need to write a recipe for it.
Writing a recipe means creating a <code class="filename">.bb</code> file that sets some
variables.
For information on variables that are useful for recipes and for information about recipe naming
issues, see the
"<a class="link" href="#ref-varlocality-recipe-required" target="_top">Required</a>"
section of the Yocto Project Reference Manual.
</p><p>
Before writing a recipe from scratch, it is often useful to check
whether someone else has written one already.
OpenEmbedded is a good place to look as it has a wider scope and range of packages.
Because the Yocto Project aims to be compatible with OpenEmbedded, most recipes
you find there should work for you.
</p><p>
For new packages, the simplest way to add a recipe is to base it on a similar
pre-existing recipe.
The sections that follow provide some examples that show how to add standard
types of packages.
</p><div class="section" title="4.3.1. Single .c File Package (Hello World!)"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-extend-addpkg-singlec"></a>4.3.1. Single .c File Package (Hello World!)</h3></div></div></div><p>
Building an application from a single file that is stored locally (e.g. under
<code class="filename">files/</code>) requires a recipe that has the file listed in
the
<code class="filename"><a class="link" href="#var-SRC_URI" target="_top">SRC_URI</a></code>
variable.
Additionally, you need to manually write the <code class="filename">do_compile</code> and
<code class="filename">do_install</code> tasks.
The <code class="filename"><a class="link" href="#var-S" target="_top">S</a></code>
variable defines the
directory containing the source code, which is set to
<code class="filename"><a class="link" href="#var-WORKDIR" target="_top">
WORKDIR</a></code> in this case - the directory BitBake uses for the build.
</p><pre class="literallayout">
DESCRIPTION = "Simple helloworld application"
SECTION = "examples"
LICENSE = "MIT"
LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"
PR = "r0"
SRC_URI = "file://helloworld.c"
S = "${WORKDIR}"
do_compile() {
${CC} helloworld.c -o helloworld
}
do_install() {
install -d ${D}${bindir}
install -m 0755 helloworld ${D}${bindir}
}
</pre><p>
</p><p>
By default, the <code class="filename">helloworld</code>, <code class="filename">helloworld-dbg</code>,
and <code class="filename">helloworld-dev</code> packages are built.
For information on how to customize the packaging process, see the
"<a class="link" href="#splitting-an-application-into-multiple-packages" title="4.3.4. Splitting an Application into Multiple Packages">Splitting an Application
into Multiple Packages</a>" section.
</p></div><div class="section" title="4.3.2. Autotooled Package"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-extend-addpkg-autotools"></a>4.3.2. Autotooled Package</h3></div></div></div><p>
Applications that use Autotools such as <code class="filename">autoconf</code> and
<code class="filename">automake</code> require a recipe that has a source archive listed in
<code class="filename"><a class="link" href="#var-SRC_URI" target="_top">SRC_URI</a></code> and
also inherits Autotools, which instructs BitBake to use the
<code class="filename">autotools.bbclass</code> file, which contains the definitions of all the steps
needed to build an Autotool-based application.
The result of the build is automatically packaged.
And, if the application uses NLS for localization, packages with local information are
generated (one package per language).
Following is one example: (<code class="filename">hello_2.3.bb</code>)
</p><pre class="literallayout">
DESCRIPTION = "GNU Helloworld application"
SECTION = "examples"
LICENSE = "GPLv2+"
LIC_FILES_CHKSUM = "file://COPYING;md5=751419260aa954499f7abaabaa882bbe"
PR = "r0"
SRC_URI = "${GNU_MIRROR}/hello/hello-${PV}.tar.gz"
inherit autotools gettext
</pre><p>
</p><p>
The variable
<code class="filename"><a class="link" href="#var-LIC_FILES_CHKSUM" target="_top">LIC_FILES_CHKSUM</a></code>
is used to track source license changes as described in the
"<a class="link" href="#usingpoky-configuring-LIC_FILES_CHKSUM" target="_top">Track License Changes</a>" section.
You can quickly create Autotool-based recipes in a manner similar to the previous example.
</p></div><div class="section" title="4.3.3. Makefile-Based Package"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-extend-addpkg-makefile"></a>4.3.3. Makefile-Based Package</h3></div></div></div><p>
Applications that use GNU <code class="filename">make</code> also require a recipe that has
the source archive listed in
<code class="filename"><a class="link" href="#var-SRC_URI" target="_top">SRC_URI</a></code>.
You do not need to add a <code class="filename">do_compile</code> step since by default BitBake
starts the <code class="filename">make</code> command to compile the application.
If you need additional <code class="filename">make</code> options you should store them in the
<code class="filename"><a class="link" href="#var-EXTRA_OEMAKE" target="_top">EXTRA_OEMAKE</a></code>
variable.
BitBake passes these options into the <code class="filename">make</code> GNU invocation.
Note that a <code class="filename">do_install</code> task is still required.
Otherwise BitBake runs an empty <code class="filename">do_install</code> task by default.
</p><p>
Some applications might require extra parameters to be passed to the compiler.
For example, the application might need an additional header path.
You can accomplish this by adding to the
<code class="filename"><a class="link" href="#var-CFLAGS" target="_top">CFLAGS</a></code> variable.
The following example shows this:
</p><pre class="literallayout">
CFLAGS_prepend = "-I ${S}/include "
</pre><p>
</p><p>
In the following example, <code class="filename">mtd-utils</code> is a makefile-based package:
</p><pre class="literallayout">
DESCRIPTION = "Tools for managing memory technology devices."
SECTION = "base"
DEPENDS = "zlib lzo e2fsprogs util-linux"
HOMEPAGE = "http://www.linux-mtd.infradead.org/"
LICENSE = "GPLv2+"
LIC_FILES_CHKSUM = "file://COPYING;md5=0636e73ff0215e8d672dc4c32c317bb3 \
file://include/common.h;beginline=1;endline=17;md5=ba05b07912a44ea2bf81ce409380049c"
SRC_URI = "git://git.infradead.org/mtd-utils.git;protocol=git;tag=995cfe51b0a3cf32f381c140bf72b21bf91cef1b \
file://add-exclusion-to-mkfs-jffs2-git-2.patch"
S = "${WORKDIR}/git/"
PR = "r1"
EXTRA_OEMAKE = "'CC=${CC}' 'RANLIB=${RANLIB}' 'AR=${AR}' \
'CFLAGS=${CFLAGS} -I${S}/include -DWITHOUT_XATTR' 'BUILDDIR=${S}'"
do_install () {
oe_runmake install DESTDIR=${D} SBINDIR=${sbindir} MANDIR=${mandir} \
INCLUDEDIR=${includedir}
install -d ${D}${includedir}/mtd/
for f in ${S}/include/mtd/*.h; do
install -m 0644 $f ${D}${includedir}/mtd/
done
}
PARALLEL_MAKE = ""
BBCLASSEXTEND = "native"
</pre><p>
</p><p>
If your sources are available as a tarball instead of a Git repository, you
will need to provide the URL to the tarball as well as an
<code class="filename">md5</code> or <code class="filename">sha256</code> sum of
the download.
Here is an example:
</p><pre class="literallayout">
SRC_URI="ftp://ftp.infradead.org/pub/mtd-utils/mtd-utils-1.4.9.tar.bz2"
SRC_URI[md5sum]="82b8e714b90674896570968f70ca778b"
</pre><p>
You can generate the <code class="filename">md5</code> or <code class="filename">sha256</code> sums
by using the <code class="filename">md5sum</code> or <code class="filename">sha256sum</code> commands
with the target file as the only argument.
Here is an example:
</p><pre class="literallayout">
$ md5sum mtd-utils-1.4.9.tar.bz2
82b8e714b90674896570968f70ca778b mtd-utils-1.4.9.tar.bz2
</pre><p>
</p></div><div class="section" title="4.3.4. Splitting an Application into Multiple Packages"><div class="titlepage"><div><div><h3 class="title"><a id="splitting-an-application-into-multiple-packages"></a>4.3.4. Splitting an Application into Multiple Packages</h3></div></div></div><p>
You can use the variables
<code class="filename"><a class="link" href="#var-PACKAGES" target="_top">PACKAGES</a></code> and
<code class="filename"><a class="link" href="#var-FILES" target="_top">FILES</a></code>
to split an application into multiple packages.
</p><p>
Following is an example that uses the <code class="filename">libXpm</code> recipe.
By default, this recipe generates a single package that contains the library along
with a few binaries.
You can modify the recipe to split the binaries into separate packages:
</p><pre class="literallayout">
require xorg-lib-common.inc
DESCRIPTION = "X11 Pixmap library"
LICENSE = "X-BSD"
LIC_FILES_CHKSUM = "file://COPYING;md5=3e07763d16963c3af12db271a31abaa5"
DEPENDS += "libxext libsm libxt"
PR = "r3"
PE = "1"
XORG_PN = "libXpm"
PACKAGES =+ "sxpm cxpm"
FILES_cxpm = "${bindir}/cxpm"
FILES_sxpm = "${bindir}/sxpm"
</pre><p>
</p><p>
In the previous example, we want to ship the <code class="filename">sxpm</code>
and <code class="filename">cxpm</code> binaries in separate packages.
Since <code class="filename">bindir</code> would be packaged into the main
<code class="filename"><a class="link" href="#var-PN" target="_top">PN</a></code>
package by default, we prepend the
<code class="filename"><a class="link" href="#var-PACKAGES" target="_top">PACKAGES</a>
</code> variable so additional package names are added to the start of list.
This results in the extra
<code class="filename"><a class="link" href="#var-FILES" target="_top">FILES</a>_*</code>
variables then containing information that define which files and
directories go into which packages.
Files included by earlier packages are skipped by latter packages.
Thus, the main
<code class="filename"><a class="link" href="#var-PN" target="_top">PN</a></code> package
does not include the above listed files.
</p></div><div class="section" title="4.3.5. Including Static Library Files"><div class="titlepage"><div><div><h3 class="title"><a id="including-static-library-files"></a>4.3.5. Including Static Library Files</h3></div></div></div><p>
If you are building a library and the library offers static linking, you can control
which static library files (<code class="filename">*.a</code> files) get included in the
built library.
</p><p>
The <code class="filename">PACKAGES</code> and <code class="filename">FILES_*</code> variables in the
<code class="filename">meta/conf/bitbake.conf</code> configuration file define how files installed
by the <code class="filename">do_install</code> task are packaged.
By default, the <code class="filename">PACKAGES</code> variable contains
<code class="filename">${PN}-staticdev</code>, which includes all static library files.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Previously released versions of the Yocto Project defined the static library files
through <code class="filename">${PN}-dev</code>.
</div><p>
Following, is part of the BitBake configuration file.
You can see where the static library files are defined:
</p><pre class="literallayout">
PACKAGES = "${PN}-dbg ${PN} ${PN}-doc ${PN}-dev ${PN}-staticdev ${PN}-locale"
PACKAGES_DYNAMIC = "${PN}-locale-*"
FILES = ""
FILES_${PN} = "${bindir}/* ${sbindir}/* ${libexecdir}/* ${libdir}/lib*${SOLIBS} \
${sysconfdir} ${sharedstatedir} ${localstatedir} \
${base_bindir}/* ${base_sbindir}/* \
${base_libdir}/*${SOLIBS} \
${datadir}/${BPN} ${libdir}/${BPN}/* \
${datadir}/pixmaps ${datadir}/applications \
${datadir}/idl ${datadir}/omf ${datadir}/sounds \
${libdir}/bonobo/servers"
FILES_${PN}-doc = "${docdir} ${mandir} ${infodir} ${datadir}/gtk-doc \
${datadir}/gnome/help"
SECTION_${PN}-doc = "doc"
FILES_${PN}-dev = "${includedir} ${libdir}/lib*${SOLIBSDEV} ${libdir}/*.la \
${libdir}/*.o ${libdir}/pkgconfig ${datadir}/pkgconfig \
${datadir}/aclocal ${base_libdir}/*.o"
SECTION_${PN}-dev = "devel"
ALLOW_EMPTY_${PN}-dev = "1"
RDEPENDS_${PN}-dev = "${PN} (= ${EXTENDPKGV})"
FILES_${PN}-staticdev = "${libdir}/*.a ${base_libdir}/*.a"
SECTION_${PN}-staticdev = "devel"
RDEPENDS_${PN}-staticdev = "${PN}-dev (= ${EXTENDPKGV})"
</pre><p>
</p></div><div class="section" title="4.3.6. Post Install Scripts"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-extend-addpkg-postinstalls"></a>4.3.6. Post Install Scripts</h3></div></div></div><p>
To add a post-installation script to a package, add a <code class="filename">pkg_postinst_PACKAGENAME()
</code> function to the <code class="filename">.bb</code> file and use
<code class="filename">PACKAGENAME</code> as the name of the package you want to attach to the
<code class="filename">postinst</code> script.
Normally
<code class="filename"><a class="link" href="#var-PN" target="_top">PN</a></code>
can be used, which automatically expands to <code class="filename">PACKAGENAME</code>.
A post-installation function has the following structure:
</p><pre class="literallayout">
pkg_postinst_PACKAGENAME () {
#!/bin/sh -e
# Commands to carry out
}
</pre><p>
</p><p>
The script defined in the post-installation function is called when the
root filesystem is created.
If the script succeeds, the package is marked as installed.
If the script fails, the package is marked as unpacked and the script is
executed when the image boots again.
</p><p>
Sometimes it is necessary for the execution of a post-installation
script to be delayed until the first boot.
For example, the script might need to be executed on the device itself.
To delay script execution until boot time, use the following structure in the
post-installation script:
</p><pre class="literallayout">
pkg_postinst_PACKAGENAME () {
#!/bin/sh -e
if [ x"$D" = "x" ]; then
# Actions to carry out on the device go here
else
exit 1
fi
}
</pre><p>
</p><p>
The previous example delays execution until the image boots again because the
<code class="filename"><a class="link" href="#var-D" target="_top">D</a></code>
variable points
to the directory containing the image when the root filesystem is created at build time but
is unset when executed on the first boot.
</p></div></div><div class="section" title="4.4. Adding a New Machine"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="platdev-newmachine"></a>4.4. Adding a New Machine</h2></div></div></div><p>
Adding a new machine to the Yocto Project is a straightforward process.
This section provides information that gives you an idea of the changes you must make.
The information covers adding machines similar to those the Yocto Project already supports.
Although well within the capabilities of the Yocto Project, adding a totally new architecture
might require
changes to <code class="filename">gcc/eglibc</code> and to the site information, which is
beyond the scope of this manual.
</p><p>
For a complete example that shows how to add a new machine,
see the
"<a class="link" href="#dev-manual-bsp-appendix" target="_top">BSP Development Example</a>"
in Appendix A.
</p><div class="section" title="4.4.1. Adding the Machine Configuration File"><div class="titlepage"><div><div><h3 class="title"><a id="platdev-newmachine-conffile"></a>4.4.1. Adding the Machine Configuration File</h3></div></div></div><p>
To add a machine configuration you need to add a <code class="filename">.conf</code> file
with details of the device being added to the <code class="filename">conf/machine/</code> file.
The name of the file determines the name the OpenEmbedded build system
uses to reference the new machine.
</p><p>
The most important variables to set in this file are as follows:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-TARGET_ARCH" target="_top">
TARGET_ARCH</a></code> (e.g. "arm")</p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-PREFERRED_PROVIDER" target="_top">
PREFERRED_PROVIDER</a></code>_virtual/kernel (see below)</p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-MACHINE_FEATURES" target="_top">
MACHINE_FEATURES</a></code> (e.g. "apm screen wifi")</p></li></ul></div><p>
</p><p>
You might also need these variables:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-SERIAL_CONSOLE" target="_top">
SERIAL_CONSOLE</a></code> (e.g. "115200 ttyS0")</p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-KERNEL_IMAGETYPE" target="_top">
KERNEL_IMAGETYPE</a></code> (e.g. "zImage")</p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-IMAGE_FSTYPES" target="_top">
IMAGE_FSTYPES</a></code> (e.g. "tar.gz jffs2")</p></li></ul></div><p>
</p><p>
You can find full details on these variables in the reference section.
You can leverage many existing machine <code class="filename">.conf</code> files from
<code class="filename">meta/conf/machine/</code>.
</p></div><div class="section" title="4.4.2. Adding a Kernel for the Machine"><div class="titlepage"><div><div><h3 class="title"><a id="platdev-newmachine-kernel"></a>4.4.2. Adding a Kernel for the Machine</h3></div></div></div><p>
The OpenEmbedded build system needs to be able to build a kernel for the machine.
You need to either create a new kernel recipe for this machine, or extend an
existing recipe.
You can find several kernel examples in the
source directory at <code class="filename">meta/recipes-kernel/linux</code>
that you can use as references.
</p><p>
If you are creating a new recipe, normal recipe-writing rules apply for setting
up a
<code class="filename"><a class="link" href="#var-SRC_URI" target="_top">SRC_URI</a></code>.
Thus, you need to specify any necessary patches and set
<code class="filename"><a class="link" href="#var-S" target="_top">S</a></code> to point at the source code.
You need to create a <code class="filename">configure</code> task that configures the
unpacked kernel with a defconfig.
You can do this by using a <code class="filename">make defconfig</code> command or,
more commonly, by copying in a suitable <code class="filename">defconfig</code> file and and then running
<code class="filename">make oldconfig</code>.
By making use of <code class="filename">inherit kernel</code> and potentially some of the
<code class="filename">linux-*.inc</code> files, most other functionality is
centralized and the the defaults of the class normally work well.
</p><p>
If you are extending an existing kernel, it is usually a matter of adding a
suitable defconfig file.
The file needs to be added into a location similar to defconfig files
used for other machines in a given kernel.
A possible way to do this is by listing the file in the
<code class="filename">SRC_URI</code> and adding the machine to the expression in
<code class="filename"><a class="link" href="#var-COMPATIBLE_MACHINE" target="_top">COMPATIBLE_MACHINE</a></code>:
</p><pre class="literallayout">
COMPATIBLE_MACHINE = '(qemux86|qemumips)'
</pre><p>
</p></div><div class="section" title="4.4.3. Adding a Formfactor Configuration File"><div class="titlepage"><div><div><h3 class="title"><a id="platdev-newmachine-formfactor"></a>4.4.3. Adding a Formfactor Configuration File</h3></div></div></div><p>
A formfactor configuration file provides information about the
target hardware for which the image is being built and information that
the build system cannot obtain from other sources such as the kernel.
Some examples of information contained in a formfactor configuration file include
framebuffer orientation, whether or not the system has a keyboard,
the positioning of the keyboard in relation to the screen, and
the screen resolution.
</p><p>
The build system uses reasonable defaults in most cases, but if customization is
necessary you need to create a <code class="filename">machconfig</code> file
in the <code class="filename">meta/recipes-bsp/formfactor/files</code>
directory.
This directory contains directories for specific machines such as
<code class="filename">qemuarm</code> and <code class="filename">qemux86</code>.
For information about the settings available and the defaults, see the
<code class="filename">meta/recipes-bsp/formfactor/files/config</code> file found in the
same area.
Following is an example for qemuarm:
</p><pre class="literallayout">
HAVE_TOUCHSCREEN=1
HAVE_KEYBOARD=1
DISPLAY_CAN_ROTATE=0
DISPLAY_ORIENTATION=0
#DISPLAY_WIDTH_PIXELS=640
#DISPLAY_HEIGHT_PIXELS=480
#DISPLAY_BPP=16
DISPLAY_DPI=150
DISPLAY_SUBPIXEL_ORDER=vrgb
</pre><p>
</p></div></div><div class="section" title="4.5. Combining Multiple Versions of Library Files into One Image"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="building-multiple-architecture-libraries-into-one-image"></a>4.5. Combining Multiple Versions of Library Files into One Image</h2></div></div></div><p>
The build system offers the ability to build libraries with different
target optimizations or architecture formats and combine these together
into one system image.
You can link different binaries in the image
against the different libraries as needed for specific use cases.
This feature is called "Multilib."
</p><p>
An example would be where you have most of a system compiled in 32-bit
mode using 32-bit libraries, but you have something large, like a database
engine, that needs to be a 64-bit application and use 64-bit libraries.
Multilib allows you to get the best of both 32-bit and 64-bit libraries.
</p><p>
While the Multilib feature is most commonly used for 32 and 64-bit differences,
the approach the build system uses facilitates different target optimizations.
You could compile some binaries to use one set of libraries and other binaries
to use other different sets of libraries.
The libraries could differ in architecture, compiler options, or other
optimizations.
</p><p>
This section overviews the Multilib process only.
For more details on how to implement Multilib, see the
<a class="ulink" href="https://wiki.yoctoproject.org/wiki/Multilib" target="_top">Multilib</a> wiki
page.
</p><div class="section" title="4.5.1. Preparing to use Multilib"><div class="titlepage"><div><div><h3 class="title"><a id="preparing-to-use-multilib"></a>4.5.1. Preparing to use Multilib</h3></div></div></div><p>
User-specific requirements drive the Multilib feature,
Consequently, there is no one "out-of-the-box" configuration that likely
exists to meet your needs.
</p><p>
In order to enable Multilib, you first need to ensure your recipe is
extended to support multiple libraries.
Many standard recipes are already extended and support multiple libraries.
You can check in the <code class="filename">meta/conf/multilib.conf</code>
configuration file in the source directory to see how this is
done using the <code class="filename">BBCLASSEXTEND</code> variable.
Eventually, all recipes will be covered and this list will be unneeded.
</p><p>
For the most part, the Multilib class extension works automatically to
extend the package name from <code class="filename">${PN}</code> to
<code class="filename">${MLPREFIX}${PN}</code>, where <code class="filename">MLPREFIX</code>
is the particular multilib (e.g. "lib32-" or "lib64-").
Standard variables such as <code class="filename">DEPENDS</code>,
<code class="filename">RDEPENDS</code>, <code class="filename">RPROVIDES</code>,
<code class="filename">RRECOMMENDS</code>, <code class="filename">PACKAGES</code>, and
<code class="filename">PACKAGES_DYNAMIC</code> are automatically extended by the system.
If you are extending any manual code in the recipe, you can use the
<code class="filename">${MLPREFIX}</code> variable to ensure those names are extended
correctly.
This automatic extension code resides in <code class="filename">multilib.bbclass</code>.
</p></div><div class="section" title="4.5.2. Using Multilib"><div class="titlepage"><div><div><h3 class="title"><a id="using-multilib"></a>4.5.2. Using Multilib</h3></div></div></div><p>
After you have set up the recipes, you need to define the actual
combination of multiple libraries you want to build.
You accomplish this through your <code class="filename">local.conf</code>
configuration file in the
<a class="link" href="#build-directory">build directory</a>.
An example configuration would be as follows:
</p><pre class="literallayout">
MACHINE = "qemux86-64"
require conf/multilib.conf
MULTILIBS = "multilib:lib32"
DEFAULTTUNE_virtclass-multilib-lib32 = "x86"
IMAGE_INSTALL = "lib32-connman"
</pre><p>
This example enables an
additional library named <code class="filename">lib32</code> alongside the
normal target packages.
When combining these "lib32" alternatives, the example uses "x86" for tuning.
For information on this particular tuning, see
<code class="filename">meta/conf/machine/include/ia32/arch-ia32.inc</code>.
</p><p>
The example then includes <code class="filename">lib32-connman</code>
in all the images, which illustrates one method of including a
multiple library dependency.
You can use a normal image build to include this dependency,
for example:
</p><pre class="literallayout">
$ bitbake core-image-sato
</pre><p>
You can also build Multilib packages specifically with a command like this:
</p><pre class="literallayout">
$ bitbake lib32-connman
</pre><p>
</p></div><div class="section" title="4.5.3. Additional Implementation Details"><div class="titlepage"><div><div><h3 class="title"><a id="additional-implementation-details"></a>4.5.3. Additional Implementation Details</h3></div></div></div><p>
Different packaging systems have different levels of native Multilib
support.
For the RPM Package Management System, the following implementation details
exist:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>A unique architecture is defined for the Multilib packages,
along with creating a unique deploy folder under
<code class="filename">tmp/deploy/rpm</code> in the
<a class="link" href="#build-directory">build directory</a>.
For example, consider <code class="filename">lib32</code> in a
<code class="filename">qemux86-64</code> image.
The possible architectures in the system are "all", "qemux86_64",
"lib32_qemux86_64", and "lib32_x86".</p></li><li class="listitem"><p>The <code class="filename">${MLPREFIX}</code> variable is stripped from
<code class="filename">${PN}</code> during RPM packaging.
The naming for a normal RPM package and a Multilib RPM package in a
<code class="filename">qemux86-64</code> system resolves to something similar to
<code class="filename">bash-4.1-r2.x86_64.rpm</code> and
<code class="filename">bash-4.1.r2.lib32_x86.rpm</code>, respectively.
</p></li><li class="listitem"><p>When installing a Multilib image, the RPM backend first
installs the base image and then installs the Multilib libraries.
</p></li><li class="listitem"><p>The build system relies on RPM to resolve the identical files in the
two (or more) Multilib packages.</p></li></ul></div><p>
</p><p>
For the IPK Package Management System, the following implementation details exist:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>The <code class="filename">${MLPREFIX}</code> is not stripped from
<code class="filename">${PN}</code> during IPK packaging.
The naming for a normal RPM package and a Multilib IPK package in a
<code class="filename">qemux86-64</code> system resolves to something like
<code class="filename">bash_4.1-r2.x86_64.ipk</code> and
<code class="filename">lib32-bash_4.1-rw_x86.ipk</code>, respectively.
</p></li><li class="listitem"><p>The IPK deploy folder is not modified with
<code class="filename">${MLPREFIX}</code> because packages with and without
the Multilib feature can exist in the same folder due to the
<code class="filename">${PN}</code> differences.</p></li><li class="listitem"><p>IPK defines a sanity check for Multilib installation
using certain rules for file comparison, overridden, etc.
</p></li></ul></div><p>
</p></div></div><div class="section" title="4.6. Configuring the Kernel"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="configuring-the-kernel"></a>4.6. Configuring the Kernel</h2></div></div></div><p>
Configuring the Yocto Project kernel consists of making sure the <code class="filename">.config</code>
file has all the right information in it for the image you are building.
You can use the <code class="filename">menuconfig</code> tool and configuration fragments to
make sure your <code class="filename">.config</code> file is just how you need it.
This section describes how to use <code class="filename">menuconfig</code>, create and use
configuration fragments, and how to interactively tweak your <code class="filename">.config</code>
file to create the leanest kernel configuration file possible.
</p><p>
For concepts on kernel configuration, see the
"<a class="link" href="#kernel-configuration" target="_top">Kernel Configuration</a>"
section in the Yocto Project Kernel Architecture and Use Manual.
</p><div class="section" title="4.6.1. Using  menuconfig"><div class="titlepage"><div><div><h3 class="title"><a id="using-menuconfig"></a>4.6.1. Using  <code class="filename">menuconfig</code></h3></div></div></div><p>
The easiest way to define kernel configurations is to set them through the
<code class="filename">menuconfig</code> tool.
For general information on <code class="filename">menuconfig</code>, see
<a class="ulink" href="http://en.wikipedia.org/wiki/Menuconfig" target="_top">http://en.wikipedia.org/wiki/Menuconfig</a>.
</p><p>
To use the <code class="filename">menuconfig</code> tool in the Yocto Project development
environment, you must build the tool using BitBake.
The following commands build and invoke <code class="filename">menuconfig</code> assuming the
source directory top-level folder is <code class="filename">~/poky</code>:
</p><pre class="literallayout">
$ cd ~/poky
$ source oe-init-build-env
$ bitbake linux-yocto -c menuconfig
</pre><p>
Once <code class="filename">menuconfig</code> comes up, its standard interface allows you to
examine and configure all the kernel configuration parameters.
Once you have made your changes, simply exit the tool and save your changes to
create an updated version of the <code class="filename">.config</code> configuration file.
</p><p>
For an example that shows how to change a specific kernel option
using <code class="filename">menuconfig</code>, see the
"<a class="link" href="#changing-the-config-smp-configuration-using-menuconfig" title="B.2.3. Changing the  CONFIG_SMP Configuration Using  menuconfig">Changing
the <code class="filename">CONFIG_SMP</code> Configuration Using <code class="filename">menuconfig</code></a>"
section.
</p></div><div class="section" title="4.6.2. Creating Configuration Fragments"><div class="titlepage"><div><div><h3 class="title"><a id="creating-config-fragments"></a>4.6.2. Creating Configuration Fragments</h3></div></div></div><p>
Configuration fragments are simply kernel options that appear in a file
placed where the OpenEmbedded build system can find and apply them.
Syntactically, the configuration statement is identical to what would appear
in the <code class="filename">.config</code> file, which is in the
<a class="link" href="#build-directory">build directory</a> in
<code class="filename">tmp/work/&lt;arch&gt;-poky-linux/linux-yocto-&lt;release-specific-string&gt;/linux-&lt;arch&gt;-&lt;build-type&gt;</code>.
</p><p>
It is simple to create a configuration fragment.
For example, issuing the following from the shell creates a configuration fragment
file named <code class="filename">my_smp.cfg</code> that enables multi-processor support
within the kernel:
</p><pre class="literallayout">
$ echo "CONFIG_SMP=y" &gt;&gt; my_smp.cfg
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
All configuration files must use the <code class="filename">.cfg</code> extension in order
for the OpenEmbedded build system to recognize them as a configuration fragment.
</div><p>
</p><p>
Where do you put your configuration files?
You can place these configuration files in the same area pointed to by
<code class="filename">SRC_URI</code>.
The OpenEmbedded build system will pick up the configuration and add it to the
kernel's configuration.
For example, suppose you had a set of configuration options in a file called
<code class="filename">myconfig.cfg</code>.
If you put that file inside a directory named <code class="filename">/linux-yocto</code>
that resides in the same directory as the kernel's append file and then add
a <code class="filename">SRC_URI</code> statement such as the following to the kernel's append file,
those configuration options will be picked up and applied when the kernel is built.
</p><pre class="literallayout">
SRC_URI += "file://myconfig.cfg"
</pre><p>
</p><p>
As mentioned earlier, you can group related configurations into multiple files and
name them all in the <code class="filename">SRC_URI</code> statement as well.
For example, you could group separate configurations specifically for Ethernet and graphics
into their own files and add those by using a <code class="filename">SRC_URI</code> statement like the
following in your append file:
</p><pre class="literallayout">
SRC_URI += "file://myconfig.cfg \
file://eth.cfg \
file://gfx.cfg"
</pre><p>
</p></div><div class="section" title="4.6.3. Fine-tuning the Kernel Configuration File"><div class="titlepage"><div><div><h3 class="title"><a id="fine-tuning-the-kernel-configuration-file"></a>4.6.3. Fine-tuning the Kernel Configuration File</h3></div></div></div><p>
You can make sure the <code class="filename">.config</code> is as lean or efficient as
possible by reading the output of the kernel configuration fragment audit,
noting any issues, making changes to correct the issues, and then repeating.
</p><p>
As part of the kernel build process, the
<code class="filename">kernel_configcheck</code> task runs.
This task validates the kernel configuration by checking the final
<code class="filename">.config</code> file against the input files.
During the check, the task produces warning messages for the following
issues:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Requested options that did not make the final
<code class="filename">.config</code> file.</p></li><li class="listitem"><p>Configuration items that appear twice in the same
configuration fragment.</p></li><li class="listitem"><p>Configuration items tagged as 'required' were overridden.
</p></li><li class="listitem"><p>A board overrides a non-board specific option.</p></li><li class="listitem"><p>Listed options not valid for the kernel being processed.
In other words, the option does not appear anywhere.</p></li></ul></div><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
The <code class="filename">kernel_configcheck</code> task can also optionally report
if an option is overridden during processing.
</div><p>
</p><p>
For each output warning, a message points to the file
that contains a list of the options and a pointer to the config
fragment that defines them.
Collectively, the files are the key to streamlining the configuration.
</p><p>
To streamline the configuration, do the following:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Start with a full configuration that you know
works - it builds and boots successfully.
This configuration file will be your baseline.</p></li><li class="listitem"><p>Separately run the <code class="filename">configme</code> and
<code class="filename">kernel_configcheck</code> tasks.</p></li><li class="listitem"><p>Take the resulting list of files from the
<code class="filename">kernel_configcheck</code> task warnings and do the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Drop values that are redefined in the fragment but do not
change the final <code class="filename">.config</code> file.</p></li><li class="listitem"><p>Analyze and potentially drop values from the
<code class="filename">.config</code> file that override required
configurations.</p></li><li class="listitem"><p>Analyze and potentially remove non-board specific options.
</p></li><li class="listitem"><p>Remove repeated and invalid options.</p></li></ul></div></li><li class="listitem"><p>After you have worked through the output of the kernel configuration
audit, you can re-run the <code class="filename">configme</code>
and <code class="filename">kernel_configcheck</code> tasks to see the results of your
changes.
If you have more issues, you can deal with them as described in the
previous step.</p></li></ol></div><p>
</p><p>
Iteratively working through steps two through four eventually yields
a minimal, streamlined configuration file.
Once you have the best <code class="filename">.config</code>, you can build the Linux
Yocto kernel.
</p></div></div><div class="section" title="4.7. Updating Existing Images"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="usingpoky-changes-updatingimages"></a>4.7. Updating Existing Images</h2></div></div></div><p>
Often, rather than re-flashing a new image, you might wish to install updated
packages into an existing running system.
You can do this by first sharing the <code class="filename">tmp/deploy/ipk/</code> directory
through a web server and then by changing <code class="filename">/etc/opkg/base-feeds.conf</code>
to point at the shared server.
Following is an example:
</p><pre class="literallayout">
$ src/gz all http://www.mysite.com/somedir/deploy/ipk/all
$ src/gz armv7a http://www.mysite.com/somedir/deploy/ipk/armv7a
$ src/gz beagleboard http://www.mysite.com/somedir/deploy/ipk/beagleboard
</pre><p>
</p></div><div class="section" title="4.8. Incrementing a Package Revision Number"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="usingpoky-changes-prbump"></a>4.8. Incrementing a Package Revision Number</h2></div></div></div><p>
If a committed change results in changing the package output,
then the value of the
<code class="filename"><a class="link" href="#var-PR" target="_top">PR</a></code>
variable needs to be increased
(or "bumped") as part of that commit.
This means that for new recipes you must be sure to add the <code class="filename">PR</code>
variable and set its initial value equal to "r0".
Failing to define <code class="filename">PR</code> makes it easy to miss when you bump a package.
Note that you can only use integer values following the "r" in the
<code class="filename">PR</code> variable.
</p><p>
If you are sharing a common <code class="filename">.inc</code> file with multiple recipes,
you can also use the
<code class="filename"><a class="link" href="#var-INC_PR" target="_top">INC_PR</a></code>
variable to ensure that
the recipes sharing the <code class="filename">.inc</code> file are rebuilt when the
<code class="filename">.inc</code> file itself is changed.
The <code class="filename">.inc</code> file must set <code class="filename">INC_PR</code>
(initially to "r0"), and all recipes referring to it should set <code class="filename">PR</code>
to "$(INC_PR).0" initially, incrementing the last number when the recipe is changed.
If the <code class="filename">.inc</code> file is changed then its
<code class="filename">INC_PR</code> should be incremented.
</p><p>
When upgrading the version of a package, assuming the
<code class="filename"><a class="link" href="#var-PV" target="_top">PV</a></code>
changes, the <code class="filename">PR</code> variable should be reset to "r0"
(or "$(INC_PR).0" if you are using <code class="filename">INC_PR</code>).
</p><p>
Usually, version increases occur only to packages.
However, if for some reason <code class="filename">PV</code> changes but does not
increase, you can increase the
<code class="filename"><a class="link" href="#var-PE" target="_top">PE</a></code>
variable (Package Epoch).
The <code class="filename">PE</code> variable defaults to "0".
</p><p>
Version numbering strives to follow the
<a class="ulink" href="http://www.debian.org/doc/debian-policy/ch-controlfields.html" target="_top">
Debian Version Field Policy Guidelines</a>.
These guidelines define how versions are compared and what "increasing" a version means.
</p><p>
There are two reasons for following the previously mentioned guidelines.
First, to ensure that when a developer updates and rebuilds, they get all the changes to
the repository and do not have to remember to rebuild any sections.
Second, to ensure that target users are able to upgrade their
devices using package manager commands such as <code class="filename">opkg upgrade</code>
(or similar commands for dpkg/apt or rpm-based systems).
</p><p>
The goal is to ensure the Yocto Project has packages that can be upgraded in all cases.
</p></div><div class="section" title="4.9. Handling a Package Name Alias"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="usingpoky-configuring-DISTRO_PN_ALIAS"></a>4.9. Handling a Package Name Alias</h2></div></div></div><p>
Sometimes a package name you are using might exist under an alias or as a similarly named
package in a different distribution.
The OpenEmbedded build system implements a <code class="filename">distro_check</code>
task that automatically connects to major distributions
and checks for these situations.
If the package exists under a different name in a different distribution, you get a
<code class="filename">distro_check</code> mismatch.
You can resolve this problem by defining a per-distro recipe name alias using the
<code class="filename"><a class="link" href="#var-DISTRO_PN_ALIAS" target="_top">DISTRO_PN_ALIAS</a></code>
variable.
</p><p>
Following is an example that shows how you specify the <code class="filename">DISTRO_PN_ALIAS</code>
variable:
</p><pre class="literallayout">
DISTRO_PN_ALIAS_pn-PACKAGENAME = "distro1=package_name_alias1 \
distro2=package_name_alias2 \
distro3=package_name_alias3 \
..."
</pre><p>
</p><p>
If you have more than one distribution alias, separate them with a space.
Note that the build system currently automatically checks the
Fedora, OpenSuSE, Debian, Ubuntu,
and Mandriva distributions for source package recipes without having to specify them
using the <code class="filename">DISTRO_PN_ALIAS</code> variable.
For example, the following command generates a report that lists the Linux distributions
that include the sources for each of the recipes.
</p><pre class="literallayout">
$ bitbake world -f -c distro_check
</pre><p>
The results are stored in the <code class="filename">build/tmp/log/distro_check-${DATETIME}.results</code>
file found in the source directory.
</p></div><div class="section" title="4.10. Building Software from an External Source"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="building-software-from-an-external-source"></a>4.10. Building Software from an External Source</h2></div></div></div><p>
By default, the OpenEmbedded build system does its work from within the
<a class="link" href="#build-directory">build directory</a>.
The build process involves fetching the source files, unpacking them, and then patching them
if necessary before the build takes place.
</p><p>
Situations exist where you might want to build software from source files that are external to
and thus outside of the <a class="link" href="#source-directory">source directory</a>.
For example, suppose you have a project that includes a new BSP with a heavily customized
kernel, a very minimal image, and some new user-space recipes.
And, you want to minimize the exposure to the build system to the
development team so that they can focus on their project and maintain everyone's workflow
as much as possible.
In this case, you want a kernel source directory on the development machine where the
development occurs.
You want the recipe's
<a class="link" href="#var-SRC_URI" target="_top"><code class="filename">SRC_URI</code></a>
variable to point to the external directory and use it as is, not copy it.
</p><p>
To build from software that comes from an external source, all you need to do is
change your recipe so that it inherits the
<a class="link" href="#ref-classes-externalsrc" target="_top"><code class="filename">externalsrc.bbclass</code></a>
class and then sets the
<a class="link" href="#var-S" target="_top"><code class="filename">S</code></a>
variable to point to your external source code.
Here are the statements to put in your recipe:
</p><pre class="literallayout">
inherit externalsrc
S = "/some/path/to/your/package/source"
</pre><p>
</p><p>
It is important to know that the <code class="filename">externalsrc.bbclass</code> assumes that the
source directory <code class="filename">S</code> and the build directory
<a class="link" href="#var-B" target="_top"><code class="filename">B</code></a>
are different even though by default these directories are the same.
This assumption is important because it supports building different variants of the recipe
by using the
<a class="link" href="#var-BBCLASSEXTEND" target="_top"><code class="filename">BBCLASSEXTEND</code></a>
variable.
You could allow the build directory to be the same as the source directory but you would
not be able to build more than one variant of the recipe.
Consequently, if you are building multiple variants of the recipe, you need to establish a
build directory that is different than the source directory.
</p></div><div class="section" title="4.11. Excluding Recipes From the Build"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="excluding-recipes-from-the-build"></a>4.11. Excluding Recipes From the Build</h2></div></div></div><p>
You might find that there are groups of recipes you want to filter
out of the build process.
For example, recipes you know you will never use or want should not
be part of the build.
Removing these recipes from parsing speeds up parts of the build.
</p><p>
It is possible to filter or mask out <code class="filename">.bb</code> and
<code class="filename">.bbappend</code> files.
You can do this by providing an expression with the
<code class="filename"><a class="link" href="#var-BBMASK" target="_top">BBMASK</a></code>
variable.
Here is an example:
</p><pre class="literallayout">
BBMASK = ".*/meta-mymachine/recipes-maybe/"
</pre><p>
Here, all <code class="filename">.bb</code> and <code class="filename">.bbappend</code> files
in the directory that match the expression are ignored during the build
process.
</p></div><div class="section" title="4.12. Using an External SCM"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="platdev-appdev-srcrev"></a>4.12. Using an External SCM</h2></div></div></div><p>
If you're working on a recipe that pulls from an external Source Code Manager (SCM), it
is possible to have the OpenEmbedded build system notice new changes added to the
SCM and then build the package that depends on them using the latest version.
This only works for SCMs from which it is possible to get a sensible revision number for changes.
Currently, you can do this with Apache Subversion (SVN), Git, and Bazaar (BZR) repositories.
</p><p>
To enable this behavior, simply add the following to the <code class="filename">local.conf</code>
configuration file found in the
<a class="link" href="#build-directory" target="_top">build directory</a>:
</p><pre class="literallayout">
SRCREV_pn-&lt;PN&gt; = "${AUTOREV}"
</pre><p>
where <code class="filename">PN</code>
is the name of the package for which you want to enable automatic source
revision updating.
</p></div><div class="section" title="4.13. Debugging With the GNU Project Debugger (GDB) Remotely"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="platdev-gdb-remotedebug"></a>4.13. Debugging With the GNU Project Debugger (GDB) Remotely</h2></div></div></div><p>
GDB allows you to examine running programs, which in turn help you to understand and fix problems.
It also allows you to perform post-mortem style analysis of program crashes.
GDB is available as a package within the Yocto Project and by default is
installed in sdk images.
See the "<a class="link" href="#ref-images" target="_top">Images</a>" chapter
in the Yocto Project Reference Manual for a description of these images.
You can find information on GDB at <a class="ulink" href="http://sourceware.org/gdb/" target="_top">http://sourceware.org/gdb/</a>.
</p><div class="tip" title="Tip" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Tip</h3>
For best results, install <code class="filename">-dbg</code> packages for the applications
you are going to debug.
Doing so makes available extra debug symbols that give you more meaningful output.
</div><p>
Sometimes, due to memory or disk space constraints, it is not possible
to use GDB directly on the remote target to debug applications.
These constraints arise because GDB needs to load the debugging information and the
binaries of the process being debugged.
Additionally, GDB needs to perform many computations to locate information such as function
names, variable names and values, stack traces and so forth - even before starting the
debugging process.
These extra computations place more load on the target system and can alter the
characteristics of the program being debugged.
</p><p>
To help get past the previously mentioned constraints, you can use Gdbserver.
Gdbserver runs on the remote target and does not load any debugging information
from the debugged process.
Instead, a GDB instance processes the debugging information that is run on a
remote computer - the host GDB.
The host GDB then sends control commands to Gdbserver to make it stop or start the debugged
program, as well as read or write memory regions of that debugged program.
All the debugging information loaded and processed as well
as all the heavy debugging is done by the host GDB.
Offloading these processes gives the Gdbserver running on the target a chance to remain
small and fast.
</p><p>
Because the host GDB is responsible for loading the debugging information and
for doing the necessary processing to make actual debugging happen, the
user has to make sure the host can access the unstripped binaries complete
with their debugging information and also be sure the target is compiled with no optimizations.
The host GDB must also have local access to all the libraries used by the
debugged program.
Because Gdbserver does not need any local debugging information, the binaries on
the remote target can remain stripped.
However, the binaries must also be compiled without optimization
so they match the host's binaries.
</p><p>
To remain consistent with GDB documentation and terminology, the binary being debugged
on the remote target machine is referred to as the "inferior" binary.
For documentation on GDB see the
<a class="ulink" href="http://sourceware.org/gdb/documentation/" target="_top">GDB site</a>.
</p><div class="section" title="4.13.1. Launching Gdbserver on the Target"><div class="titlepage"><div><div><h3 class="title"><a id="platdev-gdb-remotedebug-launch-gdbserver"></a>4.13.1. Launching Gdbserver on the Target</h3></div></div></div><p>
First, make sure Gdbserver is installed on the target.
If it is not, install the package <code class="filename">gdbserver</code>, which needs the
<code class="filename">libthread-db1</code> package.
</p><p>
As an example, to launch Gdbserver on the target and make it ready to "debug" a
program located at <code class="filename">/path/to/inferior</code>, connect
to the target and launch:
</p><pre class="literallayout">
$ gdbserver localhost:2345 /path/to/inferior
</pre><p>
Gdbserver should now be listening on port 2345 for debugging
commands coming from a remote GDB process that is running on the host computer.
Communication between Gdbserver and the host GDB are done using TCP.
To use other communication protocols, please refer to the
<a class="ulink" href="http://www.gnu.org/software/gdb/" target="_top">Gdbserver documentation</a>.
</p></div><div class="section" title="4.13.2. Launching GDB on the Host Computer"><div class="titlepage"><div><div><h3 class="title"><a id="platdev-gdb-remotedebug-launch-gdb"></a>4.13.2. Launching GDB on the Host Computer</h3></div></div></div><p>
Running GDB on the host computer takes a number of stages.
This section describes those stages.
</p><div class="section" title="4.13.2.1. Building the Cross-GDB Package"><div class="titlepage"><div><div><h4 class="title"><a id="platdev-gdb-remotedebug-launch-gdb-buildcross"></a>4.13.2.1. Building the Cross-GDB Package</h4></div></div></div><p>
A suitable GDB cross-binary is required that runs on your host computer but
also knows about the the ABI of the remote target.
You can get this binary from the meta-toolchain.
Here is an example:
</p><pre class="literallayout">
/usr/local/poky/eabi-glibc/arm/bin/arm-poky-linux-gnueabi-gdb
</pre><p>
where <code class="filename">arm</code> is the target architecture and
<code class="filename">linux-gnueabi</code> the target ABI.
</p><p>
Alternatively, you can use BitBake to build the <code class="filename">gdb-cross</code> binary.
Here is an example:
</p><pre class="literallayout">
$ bitbake gdb-cross
</pre><p>
Once the binary is built, you can find it here:
</p><pre class="literallayout">
tmp/sysroots/&lt;host-arch&gt;/usr/bin/&lt;target-abi&gt;-gdb
</pre><p>
</p></div><div class="section" title="4.13.2.2. Making the Inferior Binaries Available"><div class="titlepage"><div><div><h4 class="title"><a id="platdev-gdb-remotedebug-launch-gdb-inferiorbins"></a>4.13.2.2. Making the Inferior Binaries Available</h4></div></div></div><p>
The inferior binary (complete with all debugging symbols) as well as any
libraries (and their debugging symbols) on which the inferior binary depends
need to be available.
There are a number of ways you can make these available.
</p><p>
Perhaps the easiest way is to have an 'sdk' image that corresponds to the plain
image installed on the device.
In the case of <code class="filename">core-image-sato</code>,
<code class="filename">core-image-sato-sdk</code> would contain suitable symbols.
Because the sdk images already have the debugging symbols installed, it is just a
question of expanding the archive to some location and then informing GDB.
</p><p>
Alternatively, the OpenEmbedded build system can build a custom directory of files
for a specific
debugging purpose by reusing its <code class="filename">tmp/rootfs</code> directory.
This directory contains the contents of the last built image.
This process assumes two things:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>The image running on the target was the last image to
be built.</p></li><li class="listitem"><p>The package (<code class="filename">foo</code> in the following
example) that contains the inferior binary to be debugged has been built
without optimization and has debugging information available.</p></li></ul></div><p>
</p><p>
The following steps show how to build the custom directory of files:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Install the package (<code class="filename">foo</code> in this case) to
<code class="filename">tmp/rootfs</code>:
</p><pre class="literallayout">
$ tmp/sysroots/i686-linux/usr/bin/opkg-cl -f \
tmp/work/&lt;target-abi&gt;/core-image-sato-1.0-r0/temp/opkg.conf -o \
tmp/rootfs/ update
</pre></li><li class="listitem"><p>Install the debugging information:
</p><pre class="literallayout">
$ tmp/sysroots/i686-linux/usr/bin/opkg-cl -f \
tmp/work/&lt;target-abi&gt;/core-image-sato-1.0-r0/temp/opkg.conf \
-o tmp/rootfs install foo
$ tmp/sysroots/i686-linux/usr/bin/opkg-cl -f \
tmp/work/&lt;target-abi&gt;/core-image-sato-1.0-r0/temp/opkg.conf \
-o tmp/rootfs install foo-dbg
</pre></li></ol></div><p>
</p></div><div class="section" title="4.13.2.3. Launch the Host GDB"><div class="titlepage"><div><div><h4 class="title"><a id="platdev-gdb-remotedebug-launch-gdb-launchhost"></a>4.13.2.3. Launch the Host GDB</h4></div></div></div><p>
To launch the host GDB, you run the <code class="filename">cross-gdb</code> binary and provide
the inferior binary as part of the command line.
For example, the following command form continues with the example used in
the previous section.
This command form loads the <code class="filename">foo</code> binary
as well as the debugging information:
</p><pre class="literallayout">
$ &lt;target-abi&gt;-gdb rootfs/usr/bin/foo
</pre><p>
Once the GDB prompt appears, you must instruct GDB to load all the libraries
of the inferior binary from <code class="filename">tmp/rootfs</code> as follows:
</p><pre class="literallayout">
$ set solib-absolute-prefix /path/to/tmp/rootfs
</pre><p>
The pathname <code class="filename">/path/to/tmp/rootfs</code> must either be
the absolute path to <code class="filename">tmp/rootfs</code> or the location at which
binaries with debugging information reside.
</p><p>
At this point you can have GDB connect to the Gdbserver that is running
on the remote target by using the following command form:
</p><pre class="literallayout">
$ target remote remote-target-ip-address:2345
</pre><p>
The <code class="filename">remote-target-ip-address</code> is the IP address of the
remote target where the Gdbserver is running.
Port 2345 is the port on which the GDBSERVER is running.
</p></div><div class="section" title="4.13.2.4. Using the Debugger"><div class="titlepage"><div><div><h4 class="title"><a id="platdev-gdb-remotedebug-launch-gdb-using"></a>4.13.2.4. Using the Debugger</h4></div></div></div><p>
You can now proceed with debugging as normal - as if you were debugging
on the local machine.
For example, to instruct GDB to break in the "main" function and then
continue with execution of the inferior binary use the following commands
from within GDB:
</p><pre class="literallayout">
(gdb) break main
(gdb) continue
</pre><p>
</p><p>
For more information about using GDB, see the project's online documentation at
<a class="ulink" href="http://sourceware.org/gdb/download/onlinedocs/" target="_top">http://sourceware.org/gdb/download/onlinedocs/</a>.
</p></div></div></div><div class="section" title="4.14. Profiling with OProfile"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="platdev-oprofile"></a>4.14. Profiling with OProfile</h2></div></div></div><p>
<a class="ulink" href="http://oprofile.sourceforge.net/" target="_top">OProfile</a> is a
statistical profiler well suited for finding performance
bottlenecks in both userspace software and in the kernel.
This profiler provides answers to questions like "Which functions does my application spend
the most time in when doing X?"
Because the OpenEmbedded build system is well integrated with OProfile, it makes profiling
applications on target hardware straightforward.
</p><p>
To use OProfile, you need an image that has OProfile installed.
The easiest way to do this is with <code class="filename">tools-profile</code> in the
<code class="filename"><a class="link" href="#var-IMAGE_FEATURES" target="_top">IMAGE_FEATURES</a></code> variable.
You also need debugging symbols to be available on the system where the analysis
takes place.
You can gain access to the symbols by using <code class="filename">dbg-pkgs</code> in the
<code class="filename">IMAGE_FEATURES</code> variable or by
installing the appropriate <code class="filename">-dbg</code> packages.
</p><p>
For successful call graph analysis, the binaries must preserve the frame
pointer register and should also be compiled with the
<code class="filename">-fno-omit-framepointer</code> flag.
You can achieve this by setting the
<code class="filename"><a class="link" href="#var-SELECTED_OPTIMIZATION" target="_top">SELECTED_OPTIMIZATION</a></code>
variable to
<code class="filename">-fexpensive-optimizations -fno-omit-framepointer -frename-registers -O2</code>.
You can also achieve it by setting the
<code class="filename"><a class="link" href="#var-DEBUG_BUILD" target="_top">DEBUG_BUILD</a></code>
variable to "1" in the <code class="filename">local.conf</code> configuration file.
If you use the <code class="filename">DEBUG_BUILD</code> variable you will also add extra debug information
that can make the debug packages large.
</p><div class="section" title="4.14.1. Profiling on the Target"><div class="titlepage"><div><div><h3 class="title"><a id="platdev-oprofile-target"></a>4.14.1. Profiling on the Target</h3></div></div></div><p>
Using OProfile you can perform all the profiling work on the target device.
A simple OProfile session might look like the following:
</p><p>
</p><pre class="literallayout">
# opcontrol --reset
# opcontrol --start --separate=lib --no-vmlinux -c 5
.
.
[do whatever is being profiled]
.
.
# opcontrol --stop
$ opreport -cl
</pre><p>
</p><p>
In this example, the <code class="filename">reset</code> command clears any previously profiled data.
The next command starts OProfile.
The options used when starting the profiler separate dynamic library data
within applications, disable kernel profiling, and enable callgraphing up to
five levels deep.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
To profile the kernel, you would specify the
<code class="filename">--vmlinux=/path/to/vmlinux</code> option.
The <code class="filename">vmlinux</code> file is usually in the source directory in the
<code class="filename">/boot/</code> directory and must match the running kernel.
</div><p>
</p><p>
After you perform your profiling tasks, the next command stops the profiler.
After that, you can view results with the <code class="filename">opreport</code> command with options
to see the separate library symbols and callgraph information.
</p><p>
Callgraphing logs information about time spent in functions and about a function's
calling function (parent) and called functions (children).
The higher the callgraphing depth, the more accurate the results.
However, higher depths also increase the logging overhead.
Consequently, you should take care when setting the callgraphing depth.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
On ARM, binaries need to have the frame pointer enabled for callgraphing to work.
To accomplish this use the <code class="filename">-fno-omit-framepointer</code> option
with <code class="filename">gcc</code>.
</div><p>
</p><p>
For more information on using OProfile, see the OProfile
online documentation at
<a class="ulink" href="http://oprofile.sourceforge.net/docs/" target="_top">http://oprofile.sourceforge.net/docs/</a>.
</p></div><div class="section" title="4.14.2. Using OProfileUI"><div class="titlepage"><div><div><h3 class="title"><a id="platdev-oprofile-oprofileui"></a>4.14.2. Using OProfileUI</h3></div></div></div><p>
A graphical user interface for OProfile is also available.
You can download and build this interface from the Yocto Project at
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi/oprofileui/" target="_top">http://git.yoctoproject.org/cgit.cgi/oprofileui/</a>.
If the "tools-profile" image feature is selected, all necessary binaries
are installed onto the target device for OProfileUI interaction.
</p><p>
Even though the source directory usually includes all needed patches on the target device, you
might find you need other OProfile patches for recent OProfileUI features.
If so, see the <a class="ulink" href="http://git.yoctoproject.org/cgit.cgi/oprofileui/tree/README" target="_top">
OProfileUI README</a> for the most recent information.
</p><div class="section" title="4.14.2.1. Online Mode"><div class="titlepage"><div><div><h4 class="title"><a id="platdev-oprofile-oprofileui-online"></a>4.14.2.1. Online Mode</h4></div></div></div><p>
Using OProfile in online mode assumes a working network connection with the target
hardware.
With this connection, you just need to run "oprofile-server" on the device.
By default, OProfile listens on port 4224.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
You can change the port using the <code class="filename">--port</code> command-line
option.
</div><p>
</p><p>
The client program is called <code class="filename">oprofile-viewer</code> and its UI is relatively
straightforward.
You access key functionality through the buttons on the toolbar, which
are duplicated in the menus.
Here are the buttons:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Connect:</em></span> Connects to the remote host.
You can also supply the IP address or hostname.</p></li><li class="listitem"><p><span class="emphasis"><em>Disconnect:</em></span> Disconnects from the target.
</p></li><li class="listitem"><p><span class="emphasis"><em>Start:</em></span> Starts profiling on the device.
</p></li><li class="listitem"><p><span class="emphasis"><em>Stop:</em></span> Stops profiling on the device and
downloads the data to the local host.
Stopping the profiler generates the profile and displays it in the viewer.
</p></li><li class="listitem"><p><span class="emphasis"><em>Download:</em></span> Downloads the data from the
target and generates the profile, which appears in the viewer.</p></li><li class="listitem"><p><span class="emphasis"><em>Reset:</em></span> Resets the sample data on the device.
Resetting the data removes sample information collected from previous
sampling runs.
Be sure you reset the data if you do not want to include old sample information.
</p></li><li class="listitem"><p><span class="emphasis"><em>Save:</em></span> Saves the data downloaded from the
target to another directory for later examination.</p></li><li class="listitem"><p><span class="emphasis"><em>Open:</em></span> Loads previously saved data.
</p></li></ul></div><p>
</p><p>
The client downloads the complete 'profile archive' from
the target to the host for processing.
This archive is a directory that contains the sample data, the object files,
and the debug information for the object files.
The archive is then converted using the <code class="filename">oparchconv</code> script, which is
included in this distribution.
The script uses <code class="filename">opimport</code> to convert the archive from
the target to something that can be processed on the host.
</p><p>
Downloaded archives reside in the build directory in
<code class="filename">/tmp</code> and are cleared up when they are no longer in use.
</p><p>
If you wish to perform kernel profiling, you need to be sure
a <code class="filename">vmlinux</code> file that matches the running kernel is available.
In the source directory, that file is usually located in
<code class="filename">/boot/vmlinux-KERNELVERSION</code>, where
<code class="filename">KERNEL-version</code> is the version of the kernel.
The OpenEmbedded build system generates separate <code class="filename">vmlinux</code>
packages for each kernel it builds.
Thus, it should just be a question of making sure a matching package is
installed (e.g. <code class="filename">opkg install kernel-vmlinux</code>.
The files are automatically installed into development and profiling images
alongside OProfile.
A configuration option exists within the OProfileUI settings page that you can use to
enter the location of the <code class="filename">vmlinux</code> file.
</p><p>
Waiting for debug symbols to transfer from the device can be slow, and it
is not always necessary to actually have them on the device for OProfile use.
All that is needed is a copy of the filesystem with the debug symbols present
on the viewer system.
The "<a class="link" href="#platdev-gdb-remotedebug-launch-gdb" title="4.13.2. Launching GDB on the Host Computer">Launching GDB on the Host Computer</a>"
section covers how to create such a directory with
the source directory and how to use the OProfileUI Settings dialog to specify the location.
If you specify the directory, it will be used when the file checksums
match those on the system you are profiling.
</p></div><div class="section" title="4.14.2.2. Offline Mode"><div class="titlepage"><div><div><h4 class="title"><a id="platdev-oprofile-oprofileui-offline"></a>4.14.2.2. Offline Mode</h4></div></div></div><p>
If network access to the target is unavailable, you can generate
an archive for processing in <code class="filename">oprofile-viewer</code> as follows:
</p><pre class="literallayout">
# opcontrol --reset
# opcontrol --start --separate=lib --no-vmlinux -c 5
.
.
[do whatever is being profiled]
.
.
# opcontrol --stop
# oparchive -o my_archive
</pre><p>
</p><p>
In the above example, <code class="filename">my_archive</code> is the name of the
archive directory where you would like the profile archive to be kept.
After the directory is created, you can copy it to another host and load it
using <code class="filename">oprofile-viewer</code> open functionality.
If necessary, the archive is converted.
</p></div></div></div></div>
<div class="chapter" title="Chapter 5. Common Development Models"><div class="titlepage"><div><div><h2 class="title"><a id="dev-manual-model"></a>Chapter 5. Common Development Models</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#system-development-model">5.1. System Development Workflow</a></span></dt><dd><dl><dt><span class="section"><a href="#developing-a-board-support-package-bsp">5.1.1. Developing a Board Support Package (BSP)</a></span></dt><dt><span class="section"><a href="#modifying-the-kernel">5.1.2. Modifying the Kernel</a></span></dt></dl></dd><dt><span class="section"><a href="#application-development-workflow">5.2. Application Development Workflow</a></span></dt><dd><dl><dt><span class="section"><a href="#workflow-using-the-adt-and-eclipse">5.2.1. Workflow Using the ADT and <span class="trademark">Eclipse</span>™</a></span></dt><dt><span class="section"><a href="#adt-eclipse">5.2.2. Working Within Eclipse</a></span></dt><dt><span class="section"><a href="#workflow-using-stand-alone-cross-development-toolchains">5.2.3. Workflow Using Stand-alone Cross-development Toolchains</a></span></dt></dl></dd><dt><span class="section"><a href="#modifying-temporary-source-code">5.3. Modifying Temporary Source Code</a></span></dt><dd><dl><dt><span class="section"><a href="#finding-the-temporary-source-code">5.3.1. Finding the Temporary Source Code</a></span></dt><dt><span class="section"><a href="#using-a-quilt-workflow">5.3.2. Using a Quilt Workflow</a></span></dt><dt><span class="section"><a href="#using-a-git-workflow">5.3.3. Using a Git Workflow</a></span></dt></dl></dd><dt><span class="section"><a href="#image-development-using-hob">5.4. Image Development Using Hob</a></span></dt><dt><span class="section"><a href="#platdev-appdev-devshell">5.5. Using a Development Shell</a></span></dt></dl></div><p>
Many development models exist for which you can use the Yocto Project.
This chapter overviews the following methods:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>System Development:</em></span>
System Development covers Board Support Package (BSP) development and kernel
modification or configuration.
If you want to examine specific examples of the system development models,
see the "<a class="link" href="#dev-manual-bsp-appendix" title="Appendix A. BSP Development Example">BSP Development Example</a>"
appendix and the
"<a class="link" href="#dev-manual-kernel-appendix" title="Appendix B. Kernel Modification Example">Kernel Modification Example</a>" appendix.
</p></li><li class="listitem"><p><span class="emphasis"><em>User Application Development:</em></span>
User Application Development covers development of applications that you intend
to run on some target hardware.
For a user-space application development example that uses the
<span class="trademark">Eclipse</span>™ IDE,
see the
Yocto Project Application Developer's Guide.
</p></li><li class="listitem"><p><span class="emphasis"><em>Temporary Source Code Modification:</em></span>
Direct modification of temporary source code is a convenient development model
to quickly iterate and develop towards a solution.
Once the solution has been implemented, you should of course take steps to
get the changes upstream and applied in the affected recipes.</p></li><li class="listitem"><p><span class="emphasis"><em>Image Development using Hob:</em></span>
You can use the <a class="ulink" href="http://www.yoctoproject.org/projects/hob" target="_top">Hob</a> to build
custom operating system images within the build environment.
Hob provides an efficient interface to the OpenEmbedded build system.</p></li><li class="listitem"><p><span class="emphasis"><em>Using a Development Shell:</em></span>
You can use a <code class="filename">devshell</code> to efficiently debug commands or simply
edit packages.
Working inside a development shell is a quick way to set up the OpenEmbedded build
environment to work on parts of a project.</p></li></ul></div><p>
</p><div class="section" title="5.1. System Development Workflow"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="system-development-model"></a>5.1. System Development Workflow</h2></div></div></div><p>
System development involves modification or creation of an image that you want to run on
a specific hardware target.
Usually, when you want to create an image that runs on embedded hardware, the image does
not require the same number of features that a full-fledged Linux distribution provides.
Thus, you can create a much smaller image that is designed to use only the hardware
features for your particular hardware.
</p><p>
To help you understand how system development works in the Yocto Project, this section
covers two types of image development: BSP creation and kernel modification or
configuration.
</p><div class="section" title="5.1.1. Developing a Board Support Package (BSP)"><div class="titlepage"><div><div><h3 class="title"><a id="developing-a-board-support-package-bsp"></a>5.1.1. Developing a Board Support Package (BSP)</h3></div></div></div><p>
A BSP is a packageof recipes that, when applied, during a build results in
an image that you can run on a particular board.
Thus, the package, when compiled into the new image, supports the operation of the board.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
For a brief list of terms used when describing the development process in the Yocto Project,
see the "<a class="link" href="#yocto-project-terms" title="3.4. Yocto Project Terms">Yocto Project Terms</a>" section.
</div><p>
The remainder of this section presents the basic steps used to create a BSP
based on an existing BSP that ships with the Yocto Project.
You can reference the "<a class="link" href="#dev-manual-bsp-appendix" title="Appendix A. BSP Development Example">BSP Development Example</a>"
appendix for a detailed example that uses the Crown Bay BSP as a base BSP from which to start.
</p><p>
The following illustration and list summarize the BSP creation general workflow.
</p><p>
</p><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr style="height: 630px"><td align="center"><img src="figures/bsp-dev-flow.png" align="middle" width="540" /></td></tr></table><p>
</p><p>
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p><span class="emphasis"><em>Set up your host development system to support
development using the Yocto Project</em></span>: See the
"<a class="link" href="#the-linux-distro" target="_top">The Linux Distributions</a>"
and the
"<a class="link" href="#packages" target="_top">The Packages</a>" sections both
in the Yocto Project Quick Start for requirements.</p></li><li class="listitem"><p><span class="emphasis"><em>Establish a local copy of the project files on your
system</em></span>: You need this <a class="link" href="#source-directory">source
directory</a> available on your host system.
Having these files on your system gives you access to the build
process and to the tools you need.
For information on how to set up the source directory, see the
"<a class="link" href="#getting-setup" title="2.2. Getting Set Up">Getting Setup</a>" section.</p></li><li class="listitem"><p><span class="emphasis"><em>Establish a local copy of the base BSP files</em></span>: Having
the BSP files on your system gives you access to the build
process and to the tools you need for creating a BSP.
For information on how to get these files, see the
"<a class="link" href="#getting-setup" title="2.2. Getting Set Up">Getting Setup</a>" section.</p></li><li class="listitem"><p><span class="emphasis"><em>Choose a BSP that is supported by the Yocto Project
as your base BSP</em></span>:
The Yocto Project ships with several BSPs that support various hardware.
It is best to base your new BSP on an existing BSP rather than create all the
recipes and configuration files from scratch.
While it is possible to create everything from scratch, basing your new BSP
on something that is close is much easier.
Or, at a minimum, leveraging off an existing BSP
gives you some structure with which to start.</p><p>At this point you need to understand your target hardware well enough to determine which
existing BSP it most closely matches.
Things to consider are your hardware’s on-board features, such as CPU type and graphics support.
You should look at the README files for supported BSPs to get an idea of which one
you could use.
A generic <span class="trademark">Intel</span>®
<span class="trademark">Atom</span>™-based BSP to consider is the
Crown Bay that does not support the <span class="trademark">Intel</span>®
Embedded Media Graphics Driver (EMGD).
The remainder of this example uses that base BSP.</p><p>To see the supported BSPs, go to the
<a class="ulink" href="http://www.yoctoproject.org/download" target="_top">Download</a> page on the Yocto Project
website and click on “BSP Downloads.”</p></li><li class="listitem"><p><span class="emphasis"><em>Create your own BSP layer</em></span>: Layers are ideal for
isolating and storing work for a given piece of hardware.
A layer is really just a location or area in which you place the recipes for your BSP.
In fact, a BSP is, in itself, a special type of layer.
</p><p>
Another example that illustrates a layer is an application.
Suppose you are creating an application that has library or other dependencies in
order for it to compile and run.
The layer, in this case, would be where all the recipes that define those dependencies
are kept.
The key point for a layer is that it is an isolated area that contains
all the relevant information for the project that the OpenEmbedded build
system knows about.
For more information on layers, see the
"<a class="link" href="#understanding-and-creating-layers" title="4.1. Understanding and Creating Layers">Understanding and Creating Layers</a>"
section.
For more information on BSP layers, see the
"<a class="link" href="#bsp-layers" target="_top">BSP Layers</a>" section in the
Yocto Project Board Support Package (BSP) Developer's Guide.</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>Four BSPs exist that are part of the
Yocto Project release: <code class="filename">atom-pc</code>, <code class="filename">beagleboard</code>,
<code class="filename">mpc8315e</code>, and <code class="filename">routerstationpro</code>.
The recipes and configurations for these four BSPs are located and dispersed
within the <a class="link" href="#source-directory">source directory</a>.
On the other hand, BSP layers for Crown Bay, Emenlow, Jasper Forest,
N450, Cedar Trail, Fish River, Fish River Island II, Romley, sys940x, tlk,
and Sugar Bay exist in their own separate layers within the larger
<code class="filename">meta-intel</code> layer.</div><p>When you set up a layer for a new BSP, you should follow a standard layout.
This layout is described in the section
"<a class="link" href="#bsp-filelayout" target="_top">Example Filesystem Layout</a>"
section of the Board Support Package (BSP) Development Guide.
In the standard layout, you will notice a suggested structure for recipes and
configuration information.
You can see the standard layout for the Crown Bay BSP in this example by examining the
directory structure of the <code class="filename">meta-crownbay</code> layer inside the
source directory.</p></li><li class="listitem"><p><span class="emphasis"><em>Make configuration changes to your new BSP
layer</em></span>: The standard BSP layer structure organizes the files you need
to edit in <code class="filename">conf</code> and several <code class="filename">recipes-*</code>
directories within the BSP layer.
Configuration changes identify where your new layer is on the local system
and identify which kernel you are going to use.
</p></li><li class="listitem"><p><span class="emphasis"><em>Make recipe changes to your new BSP layer</em></span>: Recipe
changes include altering recipes (<code class="filename">.bb</code> files), removing
recipes you don't use, and adding new recipes that you need to support your hardware.
</p></li><li class="listitem"><p><span class="emphasis"><em>Prepare for the build</em></span>: Once you have made all the
changes to your BSP layer, there remains a few things
you need to do for the OpenEmbedded build system in order for it to create your image.
You need to get the build environment ready by sourcing an environment setup script
and you need to be sure two key configuration files are configured appropriately.</p><p>The entire process for building an image is overviewed in the section
"<a class="link" href="#building-image" target="_top">Building an Image</a>" section
of the Yocto Project Quick Start.
You might want to reference this information.</p></li><li class="listitem"><p><span class="emphasis"><em>Build the image</em></span>: The OpenEmbedded build system
uses the BitBake tool to build images based on the type of image you want to create.
You can find more information on BitBake
<a class="ulink" href="http://docs.openembedded.org/bitbake/html/" target="_top">here</a>.</p><p>The build process supports several types of images to satisfy different needs.
See the
"<a class="link" href="#ref-images" target="_top">Images</a>" chapter
in the Yocto Project Reference Manual for information on
supported images.</p></li></ol></div><p>
</p><p>
You can view a video presentation on "Building Custom Embedded Images with Yocto"
at <a class="ulink" href="http://free-electrons.com/blog/elc-2011-videos" target="_top">Free Electrons</a>.
You can also find supplemental information in
<a class="ulink" href="http://www.yoctoproject.org/docs/1.3/bsp-guide/bsp-guide.html" target="_top">
The Board Support Package (BSP) Development Guide</a>.
Finally, there is wiki page write up of the example also located
<a class="ulink" href="https://wiki.yoctoproject.org/wiki/Transcript:_creating_one_generic_Atom_BSP_from_another" target="_top">
here</a> that you might find helpful.
</p></div><div class="section" title="5.1.2. Modifying the Kernel"><div class="titlepage"><div><div><h3 class="title"><a id="modifying-the-kernel"></a>5.1.2. <a id="kernel-spot"></a>Modifying the Kernel</h3></div></div></div><p>
Kernel modification involves changing the Yocto Project kernel, which could involve changing
configuration options as well as adding new kernel recipes.
Configuration changes can be added in the form of configuration fragments, while recipe
modification comes through the kernel's <code class="filename">recipes-kernel</code> area
in a kernel layer you create.
</p><p>
The remainder of this section presents a high-level overview of the Yocto Project
kernel architecture and the steps to modify the kernel.
For a complete discussion of the kernel, see the
Yocto Project Kernel Architecture and Use Manual.
You can reference the appendix
"<a class="link" href="#dev-manual-kernel-appendix" title="Appendix B. Kernel Modification Example">Kernel Modification Example</a>"
for a detailed example that changes the configuration of a kernel.
</p><div class="section" title="5.1.2.1. Kernel Overview"><div class="titlepage"><div><div><h4 class="title"><a id="kernel-overview"></a>5.1.2.1. Kernel Overview</h4></div></div></div><p>
Traditionally, when one thinks of a patched kernel, they think of a base kernel
source tree and a fixed structure that contains kernel patches.
The Yocto Project, however, employs mechanisms, that in a sense, result in a kernel source
generator.
By the end of this section, this analogy will become clearer.
</p><p>
You can find a web interface to the Yocto Project kernel source repositories at
<a class="ulink" href="http://git.yoctoproject.org" target="_top">http://git.yoctoproject.org</a>.
If you look at the interface, you will see to the left a grouping of
Git repositories titled "Yocto Linux Kernel."
Within this group, you will find several kernels supported by
the Yocto Project:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><code class="filename">linux-yocto-2.6.34</code></em></span> - The
stable Yocto Project kernel that is based on the Linux 2.6.34 released kernel.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">linux-yocto-2.6.37</code></em></span> - The
stable Yocto Project kernel that is based on the Linux 2.6.37 released kernel.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">linux-yocto-3.0</code></em></span> - The stable
Yocto Project kernel that is based on the Linux 3.0 released kernel.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">linux-yocto-3.0-1.1.x</code></em></span> - The
stable Yocto Project kernel to use with the Yocto Project Release 1.1.x. This kernel
is based on the Linux 3.0 released kernel.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">linux-yocto-3.2</code></em></span> - The
stable Yocto Project kernel to use with the Yocto Project Release 1.2. This kernel
is based on the Linux 3.2 released kernel.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">linux-yocto-dev</code></em></span> - A development
kernel based on the latest upstream release candidate available.</p></li></ul></div><p>
</p><p>
The kernels are maintained using the Git revision control system
that structures them using the familiar "tree", "branch", and "leaf" scheme.
Branches represent diversions from general code to more specific code, while leaves
represent the end-points for a complete and unique kernel whose source files
when gathered from the root of the tree to the leaf accumulate to create the files
necessary for a specific piece of hardware and its features.
The following figure displays this concept:
</p><p>
</p><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr style="height: 540px"><td align="center"><img src="figures/kernel-overview-1.png" align="middle" /></td></tr></table><p>
</p><p>
</p><p>
Within the figure, the "Kernel.org Branch Point" represents the point in the tree
where a supported base kernel is modified from the Linux kernel.
For example, this could be the branch point for the <code class="filename">linux-yocto-3.0</code>
kernel.
Thus, everything further to the right in the structure is based on the
<code class="filename">linux-yocto-3.0</code> kernel.
Branch points to right in the figure represent where the
<code class="filename">linux-yocto-3.0</code> kernel is modified for specific hardware
or types of kernels, such as real-time kernels.
Each leaf thus represents the end-point for a kernel designed to run on a specific
targeted device.
</p><p>
</p><p>
The overall result is a Git-maintained repository from which all the supported
kernel types can be derived for all the supported devices.
A big advantage to this scheme is the sharing of common features by keeping them in
"larger" branches within the tree.
This practice eliminates redundant storage of similar features shared among kernels.
</p><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Keep in mind the figure does not take into account all the supported Yocto
Project kernel types, but rather shows a single generic kernel just for conceptual purposes.
Also keep in mind that this structure represents the Yocto Project source repositories
that are either pulled from during the build or established on the host development system
prior to the build by either cloning a particular kernel's Git repository or by
downloading and unpacking a tarball.
</div><p>
</p><p>
Storage of all the available kernel source code is one thing, while representing the
code on your host development system is another.
Conceptually, you can think of the kernel source repositories as all the
source files necessary for all the supported kernels.
As a developer, you are just interested in the source files for the kernel on
on which you are working.
And, furthermore, you need them available on your host system.
</p><p>
</p><p>
You make kernel source code available on your host development system by using
Git to create a bare clone of the Yocto Project kernel Git repository
in which you are interested.
Then, you use Git again to clone a copy of that bare clone.
This copy represents the directory structure on your host system that is particular
to the kernel you want.
These are the files you actually modify to change the kernel.
See the <a class="link" href="#local-kernel-files">Yocto Project Kernel</a> item earlier
in this manual for an example of how to set up the kernel source directory
structure on your host system.
</p><p>
</p><p>
This next figure illustrates how the kernel source files might be arranged on
your host system.
</p><p>
</p><p>
</p><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr style="height: 360px"><td align="center"><img src="figures/kernel-overview-3-denzil.png" align="middle" /></td></tr></table><p>
</p><p>
</p><p>
In the previous figure, the file structure on the left represents the bare clone
set up to track the Yocto Project kernel Git repository.
The structure on the right represents the copy of the bare clone.
When you make modifcations to the kernel source code, this is the area in which
you work.
Once you make corrections, you must use Git to push the committed changes to the
bare clone.
The example in <a class="xref" href="#modifying-the-kernel-source-code" title="B.1. Modifying the Kernel Source Code">Section B.1, “Modifying the Kernel Source Code”</a> provides a detailed example.
</p><p>
</p><p>
What happens during the build?
When you build the kernel on your development system all files needed for the build
are taken from the source repositories pointed to by the
<code class="filename">SRC_URI</code> variable and gathered in a temporary work area
where they are subsequently used to create the unique kernel.
Thus, in a sense, the process constructs a local source tree specific to your
kernel to generate the new kernel image - a source generator if you will.
</p><p>
The following figure shows the temporary file structure
created on your host system when the build occurs.
This build directory contains all the source files used during the build.
</p><p>
</p><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr style="height: 450px"><td align="center"><img src="figures/kernel-overview-2.png" align="middle" /></td></tr></table><p>
</p><p>
Again, for a complete discussion of the Yocto Project kernel's architecture and its
branching strategy, see the
Yocto Project Kernel Architecture and Use Manual.
You can also reference the
"<a class="link" href="#modifying-the-kernel-source-code" title="B.1. Modifying the Kernel Source Code">Modifying the Kernel Source Code</a>"
section for a detailed example that modifies the kernel.
</p></div><div class="section" title="5.1.2.2. Kernel Modification Workflow"><div class="titlepage"><div><div><h4 class="title"><a id="kernel-modification-workflow"></a>5.1.2.2. Kernel Modification Workflow</h4></div></div></div><p>
This illustration and the following list summarizes the kernel modification general workflow.
</p><p>
</p><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr style="height: 675px"><td align="center"><img src="figures/kernel-dev-flow.png" align="middle" width="540" /></td></tr></table><p>
</p><p>
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p><span class="emphasis"><em>Set up your host development system to support
development using the Yocto Project</em></span>: See
"<a class="link" href="#the-linux-distro" target="_top">The Linux Distributions</a>" and
"<a class="link" href="#packages" target="_top">The Packages</a>" sections both
in the Yocto Project Quick Start for requirements.</p></li><li class="listitem"><p><span class="emphasis"><em>Establish a local copy of project files on your
system</em></span>: Having the <a class="link" href="#source-directory">source
directory</a> on your system gives you access to the build process and tools
you need.
For information on how to get these files, see the bulleted item
"<a class="link" href="#local-yp-release">Yocto Project Release</a>" earlier in this manual.
</p></li><li class="listitem"><p><span class="emphasis"><em>Set up a local copy of the <code class="filename">poky-extras</code> Git
repository</em></span>: This local repository is the area for your configuration
fragments, new kernel recipes, and the kernel <code class="filename">.bbappend</code>
file used during the build.
It is good practice to set this repository up inside your local
source directory.
For information on how to get these files, see the bulleted item
"<a class="link" href="#poky-extras-repo">The <code class="filename">poky-extras</code> Git Repository</a>"
earlier in this manual.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>While it is certainly possible to modify the kernel without involving
a local Git repository, the suggested workflow for kernel modification
using the Yocto Project does use a Git repository.</div></li><li class="listitem"><p><span class="emphasis"><em>Establish a local copy of the Yocto Project kernel files on your
system</em></span>: In order to make modifications to the kernel you need two things:
a bare clone of the Yocto Project kernel you are modifying and
a copy of that bare clone.
The bare clone is required by the build process and is the area to which you
push your kernel source changes (pulling does not work with bare clones).
The copy of the bare clone is a local Git repository that contains all the kernel's
source files.
You make your changes to the files in this copy of the bare clone.
For information on how to set these two items up, see the bulleted item
"<a class="link" href="#local-kernel-files">Yocto Project Kernel</a>"
earlier in this manual.</p></li><li class="listitem"><p><span class="emphasis"><em>Make changes to the kernel source code if
applicable</em></span>: Modifying the kernel does not always mean directly
changing source files.
However, if you have to do this, you make the changes in the local
Git repository you set up to hold the source files (i.e. the copy of the
bare clone).
Once the changes are made, you need to use Git commands to commit the changes
and then push them to the bare clone.</p></li><li class="listitem"><p><span class="emphasis"><em>Make kernel configuration changes
if applicable</em></span>:
If your situation calls for changing the kernel's configuration, you can
use <code class="filename">menuconfig</code>
to enable and disable kernel configurations.
Using <code class="filename">menuconfig</code> allows you to interactively develop and test the
configuration changes you are making to the kernel.
When saved, changes using <code class="filename">menuconfig</code> update the kernel's
<code class="filename">.config</code>.
Try to resist the temptation of directly editing the <code class="filename">.config</code>
file found in the
<a class="link" href="#build-directory">build directory</a> at
<code class="filename">tmp/sysroots/&lt;machine-name&gt;/kernel</code>.
Doing so, can produce unexpected results when the OpenEmbedded build system
regenerates the configuration file.</p><p>Once you are satisfied with the configuration changes made using
<code class="filename">menuconfig</code>, you can directly examine the
<code class="filename">.config</code> file against a saved original and gather those
changes into a config fragment to be referenced from within the kernel's
<code class="filename">.bbappend</code> file.</p></li><li class="listitem"><p><span class="emphasis"><em>Add or extend kernel recipes if applicable</em></span>:
The standard
layer structure organizes recipe files inside the
<code class="filename">meta-kernel-dev</code> layer that is within the local
<code class="filename">poky-extras</code> Git repository.
If you need to add new kernel recipes, you add them within this layer.
Also within this area, you will find the <code class="filename">.bbappend</code>
file that appends information to the kernel's recipe file used during the
build.
</p></li><li class="listitem"><p><span class="emphasis"><em>Prepare for the build</em></span>: Once you have made all the
changes to your kernel (configurations, source code changes, recipe additions,
or recipe changes), there remains a few things
you need to do in order for the build system to create your image.
If you have not done so, you need to get the build environment ready by sourcing
the environment setup script described earlier.
You also need to be sure two key configuration files
(<code class="filename">local.conf</code> and <code class="filename">bblayers.conf</code>)
are configured appropriately.</p><p>The entire process for building an image is overviewed in the
"<a class="link" href="#building-image" target="_top">Building an Image</a>"
section of the Yocto Project Quick Start.
You might want to reference this information.
Also, you should look at the detailed examples found in the appendices at
at the end of this manual.</p></li><li class="listitem"><p><span class="emphasis"><em>Build the image</em></span>: The OpenEmbedded
build system uses the BitBake
tool to build images based on the type of image you want to create.
You can find more information on BitBake
<a class="ulink" href="http://docs.openembedded.org/bitbake/html/" target="_top">here</a>.</p><p>The build process supports several types of images to satisfy different needs.
See the "<a class="link" href="#ref-images" target="_top">Images</a>" chapter in
the Yocto Project Reference Manual for information on supported images.</p></li><li class="listitem"><p><span class="emphasis"><em>Make your configuration changes available
in the kernel layer</em></span>: Up to this point, all the configuration changes to the
kernel have been done and tested iteratively.
Once they are tested and ready to go, you can move them into the kernel layer,
which allows you to distribute the layer.</p></li><li class="listitem"><p><span class="emphasis"><em>If applicable, share your in-tree changes</em></span>:
If the changes you made
are suited for all Yocto Project kernel users, you might want to send them on
for inclusion into the upstream kernel's Git repository.
If the changes are accepted, the Yocto Project Maintainer pulls them into
the master branch of the kernel tree.
Doing so makes them available to everyone using the kernel.</p></li></ol></div><p>
</p></div></div></div><div class="section" title="5.2. Application Development Workflow"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="application-development-workflow"></a>5.2. Application Development Workflow</h2></div></div></div><p>
Application development involves creating an application that you want
to run on your target hardware, which is running a kernel image created using the
OpenEmbedded build system.
The Yocto Project provides an Application Development Toolkit (ADT) and
stand-alone cross-development toolchains that
facilitate quick development and integration of your application into its run-time environment.
Using the ADT and toolchains, you can compile and link your application.
You can then deploy your application to the actual hardware or to the QEMU emulator for testing.
If you are familiar with the popular Eclipse IDE, you can use an Eclipse Yocto Plug-in to
allow you to develop, deploy, and test your application all from within Eclipse.
</p><p>
While we strongly suggest using the ADT to develop your application, this option might not
be best for you.
If this is the case, you can still use pieces of the Yocto Project for your development process.
However, because the process can vary greatly, this manual does not provide detail on the process.
</p><div class="section" title="5.2.1. Workflow Using the ADT and Eclipse™"><div class="titlepage"><div><div><h3 class="title"><a id="workflow-using-the-adt-and-eclipse"></a>5.2.1. Workflow Using the ADT and <span class="trademark">Eclipse</span>™</h3></div></div></div><p>
To help you understand how application development works using the ADT, this section
provides an overview of the general development process and a detailed example of the process
as it is used from within the Eclipse IDE.
</p><p>
The following illustration and list summarize the application development general workflow.
</p><p>
</p><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="630"><tr style="height: 720px"><td align="center"><img src="figures/app-dev-flow.png" align="middle" /></td></tr></table><p>
</p><p>
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p><span class="emphasis"><em>Prepare the Host System for the Yocto Project</em></span>:
See
"<a class="link" href="#the-linux-distro" target="_top">The Linux Distributions</a>" and
"<a class="link" href="#packages" target="_top">The Packages</a>" sections both
in the Yocto Project Quick Start for requirements.</p></li><li class="listitem"><p><span class="emphasis"><em>Secure the Yocto Project Kernel Target Image</em></span>:
You must have a target kernel image that has been built using the OpenEmbeded
build system.</p><p>Depending on whether the Yocto Project has a pre-built image that matches your target
architecture and where you are going to run the image while you develop your application
(QEMU or real hardware), the area from which you get the image differs.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Download the image from
<a class="ulink" href="http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/machines" target="_top">
<code class="filename">machines</code></a> if your target architecture is supported
and you are going to develop and test your application on actual hardware.
</p></li><li class="listitem"><p>Download the image from the
<a class="ulink" href="http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/machines/qemu" target="_top">
<code class="filename">machines/qemu</code></a> if your target architecture is supported
and you are going to develop and test your application using the QEMU
emulator.</p></li><li class="listitem"><p>Build your image if you cannot find a pre-built image that matches
your target architecture.
If your target architecture is similar to a supported architecture, you can
modify the kernel image before you build it.
See the
"<a class="link" href="#kernel-modification-workflow" title="5.1.2.2. Kernel Modification Workflow">Kernel Modification Workflow</a>"
section earlier in this manual for information on how to create a modified
Yocto Project kernel.</p></li></ul></div><p>For information on pre-built kernel image naming schemes for images
that can run on the QEMU emulator, see the
"<a class="link" href="#downloading-the-pre-built-linux-kernel" target="_top">Downloading the Pre-Built Linux Kernel</a>"
section in the Yocto Project Quick Start.</p></li><li class="listitem"><p><span class="emphasis"><em>Install the ADT</em></span>:
The ADT provides a target-specific cross-development toolchain, the root filesystem,
the QEMU emulator, and other tools that can help you develop your application.
While it is possible to get these pieces separately, the ADT Installer provides an
easy method.
You can get these pieces by running an ADT installer script, which is configurable.
For information on how to install the ADT, see the
"<a class="link" href="#using-the-adt-installer" target="_top">Using the ADT Installer</a>"
section
in the Yocto Project Application Developer's Guide.</p></li><li class="listitem"><p><span class="emphasis"><em>If Applicable, Secure the Target Root Filesystem</em></span>:
If you choose not to install the ADT using the ADT Installer,
you need to find and download the
appropriate root filesystems.
You can find these tarballs in the same areas used for the kernel images.
Depending on the type of image you are running, the root filesystem you need differs.
For example, if you are developing an application that runs on an image that
supports Sato, you need to get root filesystem that supports Sato.
</p></li><li class="listitem"><p><span class="emphasis"><em>Create and Build your Application</em></span>:
At this point, you need to have source files for your application.
Once you have the files, you can use the Eclipse IDE to import them and build the
project.
If you are not using Eclipse, you need to use the cross-development tools you have
installed to create the image.</p></li><li class="listitem"><p><span class="emphasis"><em>Deploy the Image with the Application</em></span>:
If you are using the Eclipse IDE, you can deploy your image to the hardware or to
QEMU through the project's preferences.
If you are not using the Eclipse IDE, then you need to deploy the application using
other methods to the hardware.
Or, if you are using QEMU, you need to use that tool and load your image in for testing.
</p></li><li class="listitem"><p><span class="emphasis"><em>Test and Debug the Application</em></span>:
Once your application is deployed, you need to test it.
Within the Eclipse IDE, you can use the debubbing environment along with the
set of user-space tools installed along with the ADT to debug your application.
Of course, the same user-space tools are available separately if you choose
not to use the Eclipse IDE.</p></li></ol></div><p>
</p></div><div class="section" title="5.2.2. Working Within Eclipse"><div class="titlepage"><div><div><h3 class="title"><a id="adt-eclipse"></a>5.2.2. Working Within Eclipse</h3></div></div></div><p>
The Eclipse IDE is a popular development environment and it fully supports
development using the Yocto Project.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>This release of the Yocto Project supports both the Juno and Indigo versions
of the Eclipse IDE.
Thus, the following information provides setup information for both versions.
</div><p>
</p><p>
When you install and configure the Eclipse Yocto Project Plug-in into
the Eclipse IDE, you maximize your Yocto Project experience.
Installing and configuring the Plug-in results in an environment that
has extensions specifically designed to let you more easily develop software.
These extensions allow for cross-compilation, deployment, and execution of
your output into a QEMU emulation session.
You can also perform cross-debugging and profiling.
The environment also supports a suite of tools that allows you to perform
remote profiling, tracing, collection of power data, collection of
latency data, and collection of performance data.
</p><p>
This section describes how to install and configure the Eclipse IDE
Yocto Plug-in and how to use it to develop your application.
</p><div class="section" title="5.2.2.1. Setting Up the Eclipse IDE"><div class="titlepage"><div><div><h4 class="title"><a id="setting-up-the-eclipse-ide"></a>5.2.2.1. Setting Up the Eclipse IDE</h4></div></div></div><p>
To develop within the Eclipse IDE, you need to do the following:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Install the optimal version of the Eclipse IDE.</p></li><li class="listitem"><p>Configure the Eclipse IDE.</p></li><li class="listitem"><p>Install the Eclipse Yocto Plug-in.</p></li><li class="listitem"><p>Configure the Eclipse Yocto Plug-in.</p></li></ol></div><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Do not install Eclipse from your distribution's package repository.
Be sure to install Eclipse from the official Eclipse download site as directed
in the next section.
</div><p>
</p><div class="section" title="5.2.2.1.1. Installing the Eclipse IDE"><div class="titlepage"><div><div><h5 class="title"><a id="installing-eclipse-ide"></a>5.2.2.1.1. Installing the Eclipse IDE</h5></div></div></div><p>
It is recommended that you have the Juno 4.2 version of the
Eclipse IDE installed on your development system.
However, if you currently have the Indigo 3.7.2 version installed and you do
not want to upgrade the IDE, you can configure Indigo to work with the
Yocto Project.
See the
"<a class="link" href="#configuring-the-eclipse-ide-indigo" title="5.2.2.1.3. Configuring the Eclipse IDE (Indigo)">Configuring the Eclipse IDE (Indigo)</a>"
section.
</p><p>
If you don’t have the Juno 4.2 Eclipse IDE installed, you can find the tarball at
<a class="ulink" href="http://www.eclipse.org/downloads" target="_top">http://www.eclipse.org/downloads</a>.
From that site, choose the Eclipse Classic version particular to your development
host.
This version contains the Eclipse Platform, the Java Development
Tools (JDT), and the Plug-in Development Environment.
</p><p>
Once you have downloaded the tarball, extract it into a clean
directory.
For example, the following commands unpack and install the Eclipse IDE
tarball found in the <code class="filename">Downloads</code> area
into a clean directory using the default name <code class="filename">eclipse</code>:
</p><pre class="literallayout">
$ cd ~
$ tar -xzvf ~/Downloads/eclipse-SDK-4.2-linux-gtk-x86_64.tar.gz
</pre><p>
</p><p>
If you have the Indigo 3.7.2 Eclipse IDE already installed and you want to use that
version, one issue exists that you need to be aware of regarding the Java
Virtual machine’s garbage collection (GC) process.
The GC process does not clean up the permanent generation
space (PermGen).
This space stores metadata descriptions of classes.
The default value is set too small and it could trigger an
out-of-memory error such as the following:
</p><pre class="literallayout">
Java.lang.OutOfMemoryError: PermGen space
</pre><p>
</p><p>
This error causes the application to hang.
</p><p>
To fix this issue, you can use the <code class="filename">--vmargs</code>
option when you start the Indigo 3.7.2 Eclipse IDE
to increase the size of the permanent generation space:
</p><pre class="literallayout">
eclipse --vmargs --XX:PermSize=256M
</pre><p>
</p></div><div class="section" title="5.2.2.1.2. Configuring the Eclipse IDE (Juno)"><div class="titlepage"><div><div><h5 class="title"><a id="configuring-the-eclipse-ide-juno"></a>5.2.2.1.2. Configuring the Eclipse IDE (Juno)</h5></div></div></div><p>
This section presents the steps needed to configure the Juno 4.2 Eclipse IDE.
If you are using Indigo 3.7.2, see the
"<a class="link" href="#configuring-the-eclipse-ide-indigo" title="5.2.2.1.3. Configuring the Eclipse IDE (Indigo)">Configuring the Eclipse IDE (Indigo)</a>".
</p><p>
Before installing and configuring the Eclipse Yocto Plug-in, you need to configure
the Juno 4.2 Eclipse IDE.
Follow these general steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Start the Eclipse IDE.</p></li><li class="listitem"><p>Make sure you are in your Workbench and select
"Install New Software" from the "Help" pull-down menu.
</p></li><li class="listitem"><p>Select <code class="filename">Juno - http://download.eclipse.org/releases/juno</code>
from the "Work with:" pull-down menu.</p></li><li class="listitem"><p>Expand the box next to "Linux Tools" and select the
"LTTng - Linux Tracing Toolkit" boxes.</p></li><li class="listitem"><p>Expand the box next to "Mobile and Device Development" and select the
following boxes:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename">C/C++ Remote Launch</code></p></li><li class="listitem"><p><code class="filename">Remote System Explorer End-user Runtime</code></p></li><li class="listitem"><p><code class="filename">Remote System Explorer User Actions</code></p></li><li class="listitem"><p><code class="filename">Target Management Terminal</code></p></li><li class="listitem"><p><code class="filename">TCF Remote System Explorer add-in</code></p></li><li class="listitem"><p><code class="filename">TCF Target Explorer</code></p></li></ul></div></li><li class="listitem"><p>Expand the box next to <code class="filename">Programming Languages</code>
and select the <code class="filename">Autotools Support for CDT</code>
and <code class="filename">C/C++ Development Tools</code> boxes.</p></li><li class="listitem"><p>Complete the installation and restart the Eclipse IDE.</p></li></ol></div><p>
</p></div><div class="section" title="5.2.2.1.3. Configuring the Eclipse IDE (Indigo)"><div class="titlepage"><div><div><h5 class="title"><a id="configuring-the-eclipse-ide-indigo"></a>5.2.2.1.3. Configuring the Eclipse IDE (Indigo)</h5></div></div></div><p>
This section presents the steps needed to configure the Indigo 3.7.2 Eclipse IDE.
If you are using Juno 4.2, see the
"<a class="link" href="#configuring-the-eclipse-ide-juno" title="5.2.2.1.2. Configuring the Eclipse IDE (Juno)">Configuring the Eclipse IDE (Juno)</a>".
</p><p>
Before installing and configuring the Eclipse Yocto Plug-in, you need to configure
the Indigo 3.7.2 Eclipse IDE.
Follow these general steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Start the Eclipse IDE.</p></li><li class="listitem"><p>Make sure you are in your Workbench and select
"Install New Software" from the "Help" pull-down menu.
</p></li><li class="listitem"><p>Select <code class="filename">indigo - http://download.eclipse.org/releases/indigo</code>
from the "Work with:" pull-down menu.</p></li><li class="listitem"><p>Expand the box next to <code class="filename">Programming Languages</code>
and select the <code class="filename">Autotools Support for CDT (incubation)</code>
and <code class="filename">C/C++ Development Tools</code> boxes.</p></li><li class="listitem"><p>Expand the box next to "Linux Tools" and select the
"LTTng - Linux Tracing Toolkit(incubation)" boxes.</p></li><li class="listitem"><p>Complete the installation and restart the Eclipse IDE.</p></li><li class="listitem"><p>After the Eclipse IDE restarts and from the Workbench, select
"Install New Software" from the "Help" pull-down menu.</p></li><li class="listitem"><p>Click the
"Available Software Sites" link.</p></li><li class="listitem"><p>Check the box next to
<code class="filename">http://download.eclipse.org/tm/updates/3.3</code>
and click "OK".</p></li><li class="listitem"><p>Select <code class="filename">http://download.eclipse.org/tm/updates/3.3</code>
from the "Work with:" pull-down menu.</p></li><li class="listitem"><p>Check the box next to <code class="filename">TM and RSE Main Features</code>.
</p></li><li class="listitem"><p>Expand the box next to <code class="filename">TM and RSE Optional Add-ons</code>
and select every item except <code class="filename">RSE Unit Tests</code> and
<code class="filename">RSE WinCE Services (incubation)</code>.</p></li><li class="listitem"><p>Complete the installation and restart the Eclipse IDE.</p></li><li class="listitem"><p>If necessary, select
"Install New Software" from the "Help" pull-down menu so you can click the
"Available Software Sites" link again.</p></li><li class="listitem"><p>After clicking "Available Software Sites", check the box next to
<code class="filename">http://download.eclipse.org/tools/cdt/releases/indigo</code>
and click "OK".</p></li><li class="listitem"><p>Select <code class="filename">http://download.eclipse.orgtools/cdt/releases/indigo</code>
from the "Work with:" pull-down menu.</p></li><li class="listitem"><p>Check the box next to <code class="filename">CDT Main Features</code>.
</p></li><li class="listitem"><p>Expand the box next to <code class="filename">CDT Optional Features</code>
and select <code class="filename">C/C++ Remote Launch</code> and
<code class="filename">Target Communication Framework (incubation)</code>.</p></li><li class="listitem"><p>Complete the installation and restart the Eclipse IDE.</p></li></ol></div><p>
</p></div><div class="section" title="5.2.2.1.4. Installing or Accessing the Eclipse Yocto Plug-in"><div class="titlepage"><div><div><h5 class="title"><a id="installing-the-eclipse-yocto-plug-in"></a>5.2.2.1.4. Installing or Accessing the Eclipse Yocto Plug-in</h5></div></div></div><p>
You can install the Eclipse Yocto Plug-in into the Eclipse IDE
one of two ways: use the Yocto Project's Eclipse Update site to install the pre-built plug-in,
or build and install the plug-in from the latest source code.
If you don't want to permanently install the plug-in but just want to try it out
within the Eclipse environment, you can import the plug-in project from the
Yocto Project source repositories.
</p><div class="section" title="5.2.2.1.4.1. Installing the Pre-built Plug-in from the Yocto Project Eclipse Update Site"><div class="titlepage"><div><div><h6 class="title"><a id="new-software"></a>5.2.2.1.4.1. Installing the Pre-built Plug-in from the Yocto Project Eclipse Update Site</h6></div></div></div><p>
To install the Eclipse Yocto Plug-in from the update site,
follow these steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Start up the Eclipse IDE.</p></li><li class="listitem"><p>In Eclipse, select "Install New Software" from the "Help" menu.</p></li><li class="listitem"><p>Click "Add..." in the "Work with:" area.</p></li><li class="listitem"><p>Enter
<code class="filename">http://downloads.yoctoproject.org/releases/eclipse-plugin/1.3</code>
in the URL field and provide a meaningful name in the "Name" field.</p></li><li class="listitem"><p>Click "OK" to have the entry added to the "Work with:"
drop-down list.</p></li><li class="listitem"><p>Select the entry for the plug-in from the "Work with:" drop-down
list.</p></li><li class="listitem"><p>Check the box next to <code class="filename">Development tools and SDKs for Yocto Linux</code>.
</p></li><li class="listitem"><p>Complete the remaining software installation steps and
then restart the Eclipse IDE to finish the installation of the plug-in.
</p></li></ol></div><p>
</p></div><div class="section" title="5.2.2.1.4.2. Installing the Plug-in Using the Latest Source Code"><div class="titlepage"><div><div><h6 class="title"><a id="zip-file-method"></a>5.2.2.1.4.2. Installing the Plug-in Using the Latest Source Code</h6></div></div></div><p>
To install the Eclipse Yocto Plug-in from the latest source code, follow these steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Open a shell and create a Git repository with:
</p><pre class="literallayout">
$ git clone git://git.yoctoproject.org/eclipse-poky yocto-eclipse
</pre><p>
For this example, the repository is named
<code class="filename">~/yocto-eclipse</code>.</p></li><li class="listitem"><p>Locate the <code class="filename">build.sh</code> script in the
Git repository you created in the previous step.
The script is located in the <code class="filename">scripts</code>.</p></li><li class="listitem"><p>Be sure to set and export the <code class="filename">ECLIPSE_HOME</code> environment
variable to the top-level directory in which you installed the Indigo
version of Eclipse.
For example, if your Eclipse directory is <code class="filename">$HOME/eclipse</code>,
use the following:
</p><pre class="literallayout">
$ export ECLIPSE_HOME=$HOME/eclipse
</pre></li><li class="listitem"><p>Run the <code class="filename">build.sh</code> script and provide the
name of the Git branch along with the Yocto Project release you are
using.
Here is an example that uses the <code class="filename">master</code> Git repository
and the <code class="filename">1.1M4</code> release:
</p><pre class="literallayout">
$ scripts/build.sh master 1.1M4
</pre><p>
After running the script, the file
<code class="filename">org.yocto.sdk-&lt;release&gt;-&lt;date&gt;-archive.zip</code>
is in the current directory.</p></li><li class="listitem"><p>If necessary, start the Eclipse IDE and be sure you are in the
Workbench.</p></li><li class="listitem"><p>Select "Install New Software" from the "Help" pull-down menu.
</p></li><li class="listitem"><p>Click "Add".</p></li><li class="listitem"><p>Provide anything you want in the "Name" field.</p></li><li class="listitem"><p>Click "Archive" and browse to the ZIP file you built
in step four.
This ZIP file should not be "unzipped", and must be the
<code class="filename">*archive.zip</code> file created by running the
<code class="filename">build.sh</code> script.</p></li><li class="listitem"><p>Check the box next to the new entry in the installation window and complete
the installation.</p></li><li class="listitem"><p>Restart the Eclipse IDE if necessary.</p></li></ol></div><p>
</p><p>
At this point you should be able to configure the Eclipse Yocto Plug-in as described in the
"<a class="link" href="#configuring-the-eclipse-yocto-plug-in" title="5.2.2.1.5. Configuring the Eclipse Yocto Plug-in">Configuring the Eclipse Yocto Plug-in</a>"
section.</p></div><div class="section" title="5.2.2.1.4.3. Importing the Plug-in Project into the Eclipse Environment"><div class="titlepage"><div><div><h6 class="title"><a id="yocto-project-source"></a>5.2.2.1.4.3. Importing the Plug-in Project into the Eclipse Environment</h6></div></div></div><p>
Importing the Eclipse Yocto Plug-in project from the Yocto Project source repositories
is useful when you want to try out the latest plug-in from the tip of plug-in's
development tree.
It is important to understand when you import the plug-in you are not installing
it into the Eclipse application.
Rather, you are importing the project and just using it.
To import the plug-in project, follow these steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Open a shell and create a Git repository with:
</p><pre class="literallayout">
$ git clone git://git.yoctoproject.org/eclipse-poky yocto-eclipse
</pre><p>
For this example, the repository is named
<code class="filename">~/yocto-eclipse</code>.</p></li><li class="listitem"><p>In Eclipse, select "Import" from the "File" menu.</p></li><li class="listitem"><p>Expand the "General" box and select "existing projects into workspace"
and then click "Next".</p></li><li class="listitem"><p>Select the root directory and browse to
<code class="filename">~/yocto-eclipse/plugins</code>.</p></li><li class="listitem"><p>Three plug-ins exist: "org.yocto.bc.ui", "org.yocto.sdk.ide", and
"org.yocto.sdk.remotetools".
Select and import all of them.</p></li></ol></div><p>
</p><p>
The left navigation pane in the Eclipse application shows the default projects.
Right-click on one of these projects and run it as an Eclipse application.
This brings up a second instance of Eclipse IDE that has the Yocto Plug-in.
</p></div></div><div class="section" title="5.2.2.1.5. Configuring the Eclipse Yocto Plug-in"><div class="titlepage"><div><div><h5 class="title"><a id="configuring-the-eclipse-yocto-plug-in"></a>5.2.2.1.5. Configuring the Eclipse Yocto Plug-in</h5></div></div></div><p>
Configuring the Eclipse Yocto Plug-in involves setting the Cross
Compiler options and the Target options.
The configurations you choose become the default settings for all projects.
You do have opportunities to change them later when
you configure the project (see the following section).
</p><p>
To start, you need to do the following from within the Eclipse IDE:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Choose <code class="filename">Windows -&gt; Preferences</code> to display
the <code class="filename">Preferences</code> Dialog</p></li><li class="listitem"><p>Click <code class="filename">Yocto Project ADT</code></p></li></ul></div><p>
</p><div class="section" title="5.2.2.1.5.1. Configuring the Cross-Compiler Options"><div class="titlepage"><div><div><h6 class="title"><a id="configuring-the-cross-compiler-options"></a>5.2.2.1.5.1. Configuring the Cross-Compiler Options</h6></div></div></div><p>
To configure the Cross Compiler Options, you must select the type of toolchain,
point to the toolchain, specify the sysroot location, and select the target architecture.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Selecting the Toolchain Type:</em></span>
Choose between <code class="filename">Standalone pre-built toolchain</code>
and <code class="filename">Build system derived toolchain</code> for Cross
Compiler Options.
</p><div class="itemizedlist"><ul class="itemizedlist" type="circle"><li class="listitem"><p><span class="emphasis"><em>
<code class="filename">Standalone Pre-built Toolchain:</code></em></span>
Select this mode when you are using a stand-alone cross-toolchain.
For example, suppose you are an application developer and do not
need to build a target image.
Instead, you just want to use an architecture-specific toolchain on an
existing kernel and target root filesystem.
</p></li><li class="listitem"><p><span class="emphasis"><em>
<code class="filename">Build System Derived Toolchain:</code></em></span>
Select this mode if the cross-toolchain has been installed and built
as part of the build directory.
When you select <code class="filename">Build system derived toolchain</code>,
you are using the toolchain bundled
inside the build directory.
</p></li></ul></div><p>
</p></li><li class="listitem"><p><span class="emphasis"><em>Point to the Toolchain:</em></span>
If you are using a stand-alone pre-built toolchain, you should be pointing to the
<code class="filename">/opt/poky/1.3</code> directory.
This is the location for toolchains installed by the ADT Installer or by hand.
Sections "<a class="link" href="#configuring-and-running-the-adt-installer-script" target="_top">Configuring
and Running the ADT Installer Script</a>" and
"<a class="link" href="#using-an-existing-toolchain-tarball" target="_top">Using a Cross-Toolchain Tarball</a>"
in the Yocto Project Application Developer's Guide
describe two ways to install a stand-alone cross-toolchain in the
<code class="filename">/opt/poky</code> directory.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>It is possible to install a stand-alone cross-toolchain in a directory
other than <code class="filename">/opt/poky</code>.
However, doing so is discouraged.</div><p>If you are using a system-derived toolchain, the path you provide
for the <code class="filename">Toolchain Root Location</code>
field is the build directory.
See the "<a class="link" href="#using-the-toolchain-from-within-the-build-tree" target="_top">Using
BitBake and the build directory</a>" section in the Yocto Project Application
Developer's Guide for information on how to install the toolchain into the build
directory.</p></li><li class="listitem"><p><span class="emphasis"><em>Specify the Sysroot Location:</em></span>
This location is where the root filesystem for the
target hardware is created on the development system by the ADT Installer.
The QEMU user-space tools, the
NFS boot process, and the cross-toolchain all use the sysroot location.
</p></li><li class="listitem"><p><span class="emphasis"><em>Select the Target Architecture:</em></span>
The target architecture is the type of hardware you are
going to use or emulate.
Use the pull-down <code class="filename">Target Architecture</code> menu to make
your selection.
The pull-down menu should have the supported architectures.
If the architecture you need is not listed in the menu, you
will need to build the image.
See the "<a class="link" href="#building-image" target="_top">Building an Image</a>" section
of the Yocto Project Quick Start for more information.</p></li></ul></div><p>
</p></div><div class="section" title="5.2.2.1.5.2. Configuring the Target Options"><div class="titlepage"><div><div><h6 class="title"><a id="configuring-the-target-options"></a>5.2.2.1.5.2. Configuring the Target Options</h6></div></div></div><p>
You can choose to emulate hardware using the QEMU emulator, or you
can choose to run your image on actual hardware.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><code class="filename">QEMU:</code></em></span> Select this option if
you will be using the QEMU emulator.
If you are using the emulator, you also need to locate the kernel
and specify any custom options.</p><p>If you selected <code class="filename">Build system derived toolchain</code>,
the target kernel you built will be located in the
build directory in <code class="filename">tmp/deploy/images</code> directory.
If you selected <code class="filename">Standalone pre-built toolchain</code>, the
pre-built image you downloaded is located
in the directory you specified when you downloaded the image.</p><p>Most custom options are for advanced QEMU users to further
customize their QEMU instance.
These options are specified between paired angled brackets.
Some options must be specified outside the brackets.
In particular, the options <code class="filename">serial</code>,
<code class="filename">nographic</code>, and <code class="filename">kvm</code> must all
be outside the brackets.
Use the <code class="filename">man qemu</code> command to get help on all the options
and their use.
The following is an example:
</p><pre class="literallayout">
serial ‘&lt;-m 256 -full-screen&gt;’
</pre><p>
Regardless of the mode, Sysroot is already defined as part of the
Cross Compiler Options configuration in the
<code class="filename">Sysroot Location:</code> field.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">External HW:</code></em></span> Select this option
if you will be using actual hardware.</p></li></ul></div><p>
</p><p>
Click the <code class="filename">OK</code> button to save your plug-in configurations.
</p></div></div></div><div class="section" title="5.2.2.2. Creating the Project"><div class="titlepage"><div><div><h4 class="title"><a id="creating-the-project"></a>5.2.2.2. Creating the Project</h4></div></div></div><p>
You can create two types of projects: Autotools-based, or Makefile-based.
This section describes how to create Autotools-based projects from within
the Eclipse IDE.
For information on creating Makefile-based projects in a terminal window, see the section
"<a class="link" href="#using-the-command-line" target="_top">Using the Command Line</a>"
in the Yocto Project Application Developer's Guide.
</p><p>
To create a project based on a Yocto template and then display the source code,
follow these steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Select <code class="filename">File -&gt; New -&gt; Project</code>.</p></li><li class="listitem"><p>Double click <code class="filename">CC++</code>.</p></li><li class="listitem"><p>Double click <code class="filename">C Project</code> to create the project.</p></li><li class="listitem"><p>Expand <code class="filename">Yocto Project ADT Project</code>.</p></li><li class="listitem"><p>Select <code class="filename">Hello World ANSI C Autotools Project</code>.
This is an Autotools-based project based on a Yocto template.</p></li><li class="listitem"><p>Put a name in the <code class="filename">Project name:</code> field.
Do not use hyphens as part of the name.</p></li><li class="listitem"><p>Click <code class="filename">Next</code>.</p></li><li class="listitem"><p>Add information in the <code class="filename">Author</code> and
<code class="filename">Copyright notice</code> fields.</p></li><li class="listitem"><p>Be sure the <code class="filename">License</code> field is correct.</p></li><li class="listitem"><p>Click <code class="filename">Finish</code>.</p></li><li class="listitem"><p>If the "open perspective" prompt appears, click "Yes" so that you
in the C/C++ perspective.</p></li><li class="listitem"><p>The left-hand navigation pane shows your project.
You can display your source by double clicking the project's source file.
</p></li></ol></div><p>
</p></div><div class="section" title="5.2.2.3. Configuring the Cross-Toolchains"><div class="titlepage"><div><div><h4 class="title"><a id="configuring-the-cross-toolchains"></a>5.2.2.3. Configuring the Cross-Toolchains</h4></div></div></div><p>
The earlier section, "<a class="link" href="#configuring-the-eclipse-yocto-plug-in" title="5.2.2.1.5. Configuring the Eclipse Yocto Plug-in">Configuring
the Eclipse Yocto Plug-in</a>", sets up the default project
configurations.
You can override these settings for a given project by following these steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Select <code class="filename">Project -&gt; Change Yocto Project Settings</code>:
This selection brings up the <code class="filename">Yocot Project Settings</code> Dialog
and allows you to make changes specific to an individual project.
</p><p>By default, the Cross Compiler Options and Target Options for a project
are inherited from settings you provide using the <code class="filename">Preferences</code>
Dialog as described earlier
in the "<a class="link" href="#configuring-the-eclipse-yocto-plug-in" title="5.2.2.1.5. Configuring the Eclipse Yocto Plug-in">Configuring the Eclipse
Yocto Plug-in</a>" section.
The <code class="filename">Yocto Project Settings</code>
Dialog allows you to override those default settings
for a given project.</p></li><li class="listitem"><p>Make your configurations for the project and click "OK".</p></li><li class="listitem"><p>Select <code class="filename">Project -&gt; Reconfigure Project</code>:
This selection reconfigures the project by running
<code class="filename">autogen.sh</code> in the workspace for your project.
The script also runs <code class="filename">libtoolize</code>, <code class="filename">aclocal</code>,
<code class="filename">autoconf</code>, <code class="filename">autoheader</code>,
<code class="filename">automake --a</code>, and
<code class="filename">./configure</code>.
Click on the <code class="filename">Console</code> tab beneath your source code to
see the results of reconfiguring your project.</p></li></ol></div><p>
</p></div><div class="section" title="5.2.2.4. Building the Project"><div class="titlepage"><div><div><h4 class="title"><a id="building-the-project"></a>5.2.2.4. Building the Project</h4></div></div></div><p>
To build the project, select <code class="filename">Project -&gt; Build Project</code>.
The console should update and you can note the cross-compiler you are using.
</p></div><div class="section" title="5.2.2.5. Starting QEMU in User Space NFS Mode"><div class="titlepage"><div><div><h4 class="title"><a id="starting-qemu-in-user-space-nfs-mode"></a>5.2.2.5. Starting QEMU in User Space NFS Mode</h4></div></div></div><p>
To start the QEMU emulator from within Eclipse, follow these steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Expose the <code class="filename">Run -&gt; External Tools</code> menu.
Your image should appear as a selectable menu item.
</p></li><li class="listitem"><p>Select your image from the menu to launch the
emulator in a new window.</p></li><li class="listitem"><p>If needed, enter your host root password in the shell window at the prompt.
This sets up a <code class="filename">Tap 0</code> connection needed for running in user-space
NFS mode.</p></li><li class="listitem"><p>Wait for QEMU to launch.</p></li><li class="listitem"><p>Once QEMU launches, you can begin operating within that
environment.
For example, you could determine the IP Address
for the user-space NFS by using the <code class="filename">ifconfig</code> command.
</p></li></ol></div><p>
</p></div><div class="section" title="5.2.2.6. Deploying and Debugging the Application"><div class="titlepage"><div><div><h4 class="title"><a id="deploying-and-debugging-the-application"></a>5.2.2.6. Deploying and Debugging the Application</h4></div></div></div><p>
Once the QEMU emulator is running the image, using the Eclipse IDE
you can deploy your application and use the emulator to perform debugging.
Follow these steps to deploy the application.
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Select <code class="filename">Run -&gt; Debug Configurations...</code></p></li><li class="listitem"><p>In the left area, expand <code class="filename">C/C++Remote Application</code>.</p></li><li class="listitem"><p>Locate your project and select it to bring up a new
tabbed view in the <code class="filename">Debug Configurations</code> Dialog.</p></li><li class="listitem"><p>Enter the absolute path into which you want to deploy
the application.
Use the <code class="filename">Remote Absolute File Path for C/C++Application:</code> field.
For example, enter <code class="filename">/usr/bin/&lt;programname&gt;</code>.</p></li><li class="listitem"><p>Click on the <code class="filename">Debugger</code> tab to see the cross-tool debugger
you are using.</p></li><li class="listitem"><p>Click on the <code class="filename">Main</code> tab.</p></li><li class="listitem"><p>Create a new connection to the QEMU instance
by clicking on <code class="filename">new</code>.</p></li><li class="listitem"><p>Select <code class="filename">TCF</code>, which means Target Communication
Framework.</p></li><li class="listitem"><p>Click <code class="filename">Next</code>.</p></li><li class="listitem"><p>Clear out the <code class="filename">host name</code> field and enter the IP Address
determined earlier.</p></li><li class="listitem"><p>Click <code class="filename">Finish</code> to close the
<code class="filename">New Connections</code> Dialog.</p></li><li class="listitem"><p>Use the drop-down menu now in the <code class="filename">Connection</code> field and pick
the IP Address you entered.</p></li><li class="listitem"><p>Click <code class="filename">Debug</code> to bring up a login screen
and login.</p></li><li class="listitem"><p>Accept the debug perspective.</p></li></ol></div><p>
</p></div><div class="section" title="5.2.2.7. Running User-Space Tools"><div class="titlepage"><div><div><h4 class="title"><a id="running-user-space-tools"></a>5.2.2.7. Running User-Space Tools</h4></div></div></div><p>
As mentioned earlier in the manual, several tools exist that enhance
your development experience.
These tools are aids in developing and debugging applications and images.
You can run these user-space tools from within the Eclipse IDE through the
<code class="filename">YoctoTools</code> menu.
</p><p>
Once you pick a tool, you need to configure it for the remote target.
Every tool needs to have the connection configured.
You must select an existing TCF-based RSE connection to the remote target.
If one does not exist, click <code class="filename">New</code> to create one.
</p><p>
Here are some specifics about the remote tools:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><code class="filename">OProfile</code>:</em></span> Selecting this tool causes
the <code class="filename">oprofile-server</code> on the remote target to launch on
the local host machine.
The <code class="filename">oprofile-viewer</code> must be installed on the local host machine and the
<code class="filename">oprofile-server</code> must be installed on the remote target,
respectively, in order to use.
You must compile and install the <code class="filename">oprofile-viewer</code> from the source code
on your local host machine.
Furthermore, in order to convert the target's sample format data into a form that the
host can use, you must have <code class="filename">oprofile</code> version 0.9.4 or
greater installed on the host.</p><p>You can locate both the viewer and server from
<a class="ulink" href="http://git.yoctoproject.org/cgit/cgit.cgi/oprofileui/" target="_top">http://git.yoctoproject.org/cgit/cgit.cgi/oprofileui/</a>.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>The <code class="filename">oprofile-server</code> is installed by default on
the <code class="filename">core-image-sato-sdk</code> image.</div></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">Lttng-ust</code>:</em></span> Selecting this tool runs
<code class="filename">usttrace</code> on the remote target, transfers the output data back
to the local host machine, and uses the <code class="filename">lttng</code> Eclipse plug-in to
graphically display the output.
For information on how to use <code class="filename">lttng</code> to trace an application, see
<a class="ulink" href="http://lttng.org/files/ust/manual/ust.html" target="_top">http://lttng.org/files/ust/manual/ust.html</a>.</p><p>For <code class="filename">Application</code>, you must supply the absolute path name of the
application to be traced by user mode <code class="filename">lttng</code>.
For example, typing <code class="filename">/path/to/foo</code> triggers
<code class="filename">usttrace /path/to/foo</code> on the remote target to trace the
program <code class="filename">/path/to/foo</code>.</p><p><code class="filename">Argument</code> is passed to <code class="filename">usttrace</code>
running on the remote target.</p><p>Before you use the <code class="filename">lttng-ust</code> tool, you need to setup
the <code class="filename">lttng</code> Eclipse plug-in and create a <code class="filename">lttng</code>
project.
Do the following:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Follow these
<a class="ulink" href="http://wiki.eclipse.org/Linux_Tools_Project/LTTng#Downloading_and_installing_the_LTTng_parser_library" target="_top">instructions</a>
to download and install the <code class="filename">lttng</code> parser library.
</p></li><li class="listitem"><p>Select <code class="filename">Window -&gt; Open Perspective -&gt; Other</code>
and then select <code class="filename">LTTng</code>.</p></li><li class="listitem"><p>Click <code class="filename">OK</code> to change the Eclipse perspective
into the <code class="filename">LTTng</code> perspective.</p></li><li class="listitem"><p>Create a new <code class="filename">LTTng</code> project by selecting
<code class="filename">File -&gt; New -&gt; Project</code>.</p></li><li class="listitem"><p>Choose <code class="filename">LTTng -&gt; LTTng Project</code>.</p></li><li class="listitem"><p>Click <code class="filename">YoctoTools -&gt; lttng-ust</code> to start user mode
<code class="filename">lttng</code> on the remote target.</p></li></ol></div><p>After the output data has been transferred from the remote target back to the local
host machine, new traces will be imported into the selected <code class="filename">LTTng</code> project.
Then you can go to the <code class="filename">LTTng</code> project, right click the imported
trace, and set the trace type as the <code class="filename">LTTng</code> kernel trace.
Finally, right click the imported trace and select <code class="filename">Open</code>
to display the data graphically.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">PowerTOP</code>:</em></span> Selecting this tool runs
<code class="filename">powertop</code> on the remote target machine and displays the results in a
new view called <code class="filename">powertop</code>.</p><p><code class="filename">Time to gather data(sec):</code> is the time passed in seconds before data
is gathered from the remote target for analysis.</p><p><code class="filename">show pids in wakeups list:</code> corresponds to the
<code class="filename">-p</code> argument
passed to <code class="filename">powertop</code>.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">LatencyTOP and Perf</code>:</em></span>
<code class="filename">latencytop</code> identifies system latency, while
<code class="filename">perf</code> monitors the system's
performance counter registers.
Selecting either of these tools causes an RSE terminal view to appear
from which you can run the tools.
Both tools refresh the entire screen to display results while they run.</p></li></ul></div><p>
</p></div><div class="section" title="5.2.2.8. Customizing an Image Using a BitBake Commander Project and Hob"><div class="titlepage"><div><div><h4 class="title"><a id="customizing-an-image-using-a-bitbake-commander-project-and-hob"></a>5.2.2.8. Customizing an Image Using a BitBake Commander Project and Hob</h4></div></div></div><p>
Within Eclipse, you can create a Yocto BitBake Commander project,
edit the metadata, and then use the
<a class="ulink" href="http://www.yoctoproject.org/projects/hob" target="_top">Hob</a> to build a customized
image all within one IDE.
</p><div class="section" title="5.2.2.8.1. Creating the Yocto BitBake Commander Project"><div class="titlepage"><div><div><h5 class="title"><a id="creating-the-yocto-bitbake-commander-project"></a>5.2.2.8.1. Creating the Yocto BitBake Commander Project</h5></div></div></div><p>
To create a Yocto BitBake Commander project, follow these steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Select <code class="filename">Window -&gt; Open Perspective -&gt; Other</code>
and then choose <code class="filename">Bitbake Commander</code>.</p></li><li class="listitem"><p>Click <code class="filename">OK</code> to change the Eclipse perspective into the
Bitbake Commander perspective.</p></li><li class="listitem"><p>Select <code class="filename">File -&gt; New -&gt; Project</code> to create a new Yocto
Bitbake Commander project.</p></li><li class="listitem"><p>Choose <code class="filename">Yocto Project Bitbake Commander -&gt; New Yocto Project</code>
and click <code class="filename">Next</code>.</p></li><li class="listitem"><p>Enter the Project Name and choose the Project Location.
The Yocto project's metadata files will be put under the directory
<code class="filename">&lt;project_location&gt;/&lt;project_name&gt;</code>.
If that directory does not exist, you need to check
the "Clone from Yocto Git Repository" box, which would execute a
<code class="filename">git clone</code> command to get the project's metadata files.
</p></li><li class="listitem"><p>Select <code class="filename">Finish</code> to create the project.</p></li></ol></div><p>
</p></div><div class="section" title="5.2.2.8.2. Editing the Metadata Files"><div class="titlepage"><div><div><h5 class="title"><a id="editing-the-metadata-files"></a>5.2.2.8.2. Editing the Metadata Files</h5></div></div></div><p>
After you create the Yocto Bitbake Commander project, you can modify the metadata files
by opening them in the project.
When editing recipe files (<code class="filename">.bb</code> files), you can view BitBake
variable values and information by hovering the mouse pointer over the variable name and
waiting a few seconds.
</p><p>
To edit the metadata, follow these steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Select your Yocto Bitbake Commander project.</p></li><li class="listitem"><p>Select <code class="filename">File -&gt; New -&gt; Yocto BitBake Commander -&gt; BitBake Recipe</code>
to open a new recipe wizard.</p></li><li class="listitem"><p>Point to your source by filling in the "SRC_URL" field.
For example, you can add a recipe to your
<a class="link" href="#source-directory" target="_top">source directory</a>
by defining "SRC_URL" as follows:
</p><pre class="literallayout">
ftp://ftp.gnu.org/gnu/m4/m4-1.4.9.tar.gz
</pre></li><li class="listitem"><p>Click "Populate" to calculate the archive md5, sha256,
license checksum values and to auto-generate the recipe filename.</p></li><li class="listitem"><p>Fill in the "Description" field.</p></li><li class="listitem"><p>Be sure values for all required fields exist.</p></li><li class="listitem"><p>Click <code class="filename">Finish</code>.</p></li></ol></div><p>
</p></div><div class="section" title="5.2.2.8.3. Building and Customizing the Image"><div class="titlepage"><div><div><h5 class="title"><a id="buiding-and-customizing-the-image"></a>5.2.2.8.3. Building and Customizing the Image</h5></div></div></div><p>
To build and customize the image in Eclipse, follow these steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Select your Yocto Bitbake Commander project.</p></li><li class="listitem"><p>Select <code class="filename">Project -&gt; Launch HOB</code>.</p></li><li class="listitem"><p>Enter the build directory where you want to put your final images.</p></li><li class="listitem"><p>Click <code class="filename">OK</code> to launch Hob.</p></li><li class="listitem"><p>Use Hob to customize and build your own images.
For information on Hob, see the
<a class="ulink" href="http://www.yoctoproject.org/projects/hob" target="_top">Hob Project Page</a> on the
Yocto Project website.</p></li></ol></div><p>
</p></div></div></div><div class="section" title="5.2.3. Workflow Using Stand-alone Cross-development Toolchains"><div class="titlepage"><div><div><h3 class="title"><a id="workflow-using-stand-alone-cross-development-toolchains"></a>5.2.3. Workflow Using Stand-alone Cross-development Toolchains</h3></div></div></div><p>
If you want to develop an application without prior installation of the ADT, you
still can employ the cross-development toolchain, the QEMU emulator, and a number of supported
target image files.
You just need to follow these general steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p><span class="emphasis"><em>Install the cross-development toolchain for your target hardware:</em></span>
For information on how to install the toolchain, see the
"<a class="link" href="#using-an-existing-toolchain-tarball" target="_top">Using a Cross-Toolchain Tarball</a>"
section
in the Yocto Project Application Developer's Guide.</p></li><li class="listitem"><p><span class="emphasis"><em>Download the Target Image:</em></span> The Yocto Project supports
several target architectures and has many pre-built kernel images and root filesystem
images.</p><p>If you are going to develop your application on hardware, go to the
<a class="ulink" href="http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/machines" target="_top"><code class="filename">machines</code></a>
download area and choose a target machine area
from which to download the kernel image and root filesystem.
This download area could have several files in it that support development using
actual hardware.
For example, the area might contain <code class="filename">.hddimg</code> files that combine the
kernel image with the filesystem, boot loaders, etc.
Be sure to get the files you need for your particular development process.</p><p>If you are going to develop your application and then run and test it using the QEMU
emulator, go to the
<a class="ulink" href="http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/machines/qemu" target="_top"><code class="filename">machines/qemu</code></a>
download area.
From this area, go down into the directory for your target architecture
(e.g. <code class="filename">qemux86_64</code> for an
<span class="trademark">Intel</span>®-based 64-bit architecture).
Download kernel, root filesystem, and any other files you need for your process.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>In order to use the root filesystem in QEMU, you need to extract it.
See the
"<a class="link" href="#extracting-the-root-filesystem" target="_top">Extracting the Root Filesystem</a>"
section for information on how to extract the root filesystem.</div></li><li class="listitem"><p><span class="emphasis"><em>Develop and Test your Application:</em></span> At this point,
you have the tools to develop your application.
If you need to separately install and use the QEMU emulator, you can go to
<a class="ulink" href="http://www.qemu.org" target="_top">QEMU Home Page</a> to download and learn about the
emulator.</p></li></ol></div><p>
</p></div></div><div class="section" title="5.3. Modifying Temporary Source Code"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="modifying-temporary-source-code"></a>5.3. Modifying Temporary Source Code</h2></div></div></div><p>
You might
find it helpful during development to modify the temporary source code used by recipes
to build packages.
For example, suppose you are developing a patch and you need to experiment a bit
to figure out your solution.
After you have initially built the package, you can iteratively tweak the
source code, which is located in the
<a class="link" href="#build-directory">build directory</a>, and then
you can force a re-compile and quickly test your altered code.
Once you settle on a solution, you can then preserve your changes in the form of
patches.
You can accomplish these steps all within either a
<a class="ulink" href="http://savannah.nongnu.org/projects/quilt" target="_top">Quilt</a> or
<a class="link" href="#git" title="3.6. Git">Git</a> workflow.
</p><div class="section" title="5.3.1. Finding the Temporary Source Code"><div class="titlepage"><div><div><h3 class="title"><a id="finding-the-temporary-source-code"></a>5.3.1. Finding the Temporary Source Code</h3></div></div></div><p>
During a build, the unpacked temporary source code used by recipes
to build packages is available in the build directory as
defined by the
<code class="filename"><a class="link" href="#var-S" target="_top">S</a></code> variable.
Below is the default value for the <code class="filename">S</code> variable as defined in the
<code class="filename">meta/conf/bitbake.conf</code> configuration file in the
<a class="link" href="#source-directory">source directory</a>:
</p><pre class="literallayout">
S = ${WORKDIR}/${BP}
</pre><p>
You should be aware that many recipes override the <code class="filename">S</code> variable.
For example, recipes that fetch their source from Git usually set
<code class="filename">S</code> to <code class="filename">${WORKDIR}/git</code>.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><code class="filename">BP</code> represents the "Base Package", which is the base package
name and the package version:
<pre class="literallayout">
BP = ${BPN}-${PV}
</pre></div><p>
</p><p>
The path to the work directory for the recipe
(<a class="link" href="#var-WORKDIR" target="_top"><code class="filename">WORKDIR</code></a>) depends
on the package name and the architecture of the target device.
For example, here is the work directory for packages whose targets are not device-dependent:
</p><pre class="literallayout">
${TMPDIR}/work/${PACKAGE_ARCH}-poky-${TARGET_OS}/${PN}-${PV}-${PR}
</pre><p>
Let's look at an example without variables.
Assuming a top-level source directory named <code class="filename">poky</code>
and a default build directory of <code class="filename">poky/build</code>,
the following is the work directory for the <code class="filename">acl</code> package:
</p><pre class="literallayout">
~/poky/build/tmp/work/i586-poky-linux/acl-2.2.51-r3
</pre><p>
</p><p>
If your package is dependent on the target device, the work directory varies slightly:
</p><pre class="literallayout">
${TMPDIR}/work/${MACHINE}-poky-${TARGET_OS}/${PN}-${PV}-${PR}
</pre><p>
Again, assuming top-level source directory named <code class="filename">poky</code>
and a default build directory of <code class="filename">poky/build</code>, the
following is the work directory for the <code class="filename">acl</code> package that is being
built for a MIPS-based device:
</p><pre class="literallayout">
~/poky/build/tmp/work/mips-poky-linux/acl-2.2.51-r2
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
To better understand how the OpenEmbedded build system resolves directories during the
build process, see the glossary entries for the
<a class="link" href="#var-WORKDIR" target="_top"><code class="filename">WORKDIR</code></a>,
<a class="link" href="#var-TMPDIR" target="_top"><code class="filename">TMPDIR</code></a>,
<a class="link" href="#var-TOPDIR" target="_top"><code class="filename">TOPDIR</code></a>,
<a class="link" href="#var-PACKAGE_ARCH" target="_top"><code class="filename">PACKAGE_ARCH</code></a>,
<a class="link" href="#var-TARGET_OS" target="_top"><code class="filename">TARGET_OS</code></a>,
<a class="link" href="#var-PN" target="_top"><code class="filename">PN</code></a>,
<a class="link" href="#var-PV" target="_top"><code class="filename">PV</code></a>,
and
<a class="link" href="#var-PR" target="_top"><code class="filename">PR</code></a>
variables in the Yocto Project Reference Manual.
</div><p>
Now that you know where to locate the directory that has the temporary source code, you can use a
Quilt or Git workflow to make your edits, test the changes, and preserve the
changes in the form of patches.
</p></div><div class="section" title="5.3.2. Using a Quilt Workflow"><div class="titlepage"><div><div><h3 class="title"><a id="using-a-quilt-workflow"></a>5.3.2. Using a Quilt Workflow</h3></div></div></div><p>
<a class="ulink" href="http://savannah.nongnu.org/projects/quilt" target="_top">Quilt</a>
is a powerful tool that allows you to capture source code changes without having
a clean source tree.
This section outlines the typical workflow you can use to modify temporary source code,
test changes, and then preserve the changes in the form of a patch all using Quilt.
</p><p>
Follow these general steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p><span class="emphasis"><em>Find the Source Code:</em></span>
The temporary source code used by the OpenEmbedded build system is kept in the
build directory.
See the
"<a class="link" href="#finding-the-temporary-source-code" title="5.3.1. Finding the Temporary Source Code">Finding the Temporary Source Code</a>"
section to learn how to locate the directory that has the temporary source code for a
particular package.</p></li><li class="listitem"><p><span class="emphasis"><em>Change Your Working Directory:</em></span>
You need to be in the directory that has the temporary source code.
That directory is defined by the
<a class="link" href="#var-S" target="_top">S</a>
variable.</p></li><li class="listitem"><p><span class="emphasis"><em>Create a New Patch:</em></span>
Before modifying source code, you need to create a new patch.
To create a new patch file, use <code class="filename">quilt new</code> as below:
</p><pre class="literallayout">
$ quilt new my_changes.patch
</pre></li><li class="listitem"><p><span class="emphasis"><em>Notify Quilt and Add Files:</em></span>
After creating the patch, you need to notify Quilt about the files you will
be changing.
Add the files you will be modifying into the patch you just created:
</p><pre class="literallayout">
$ quilt add file1.c file2.c file3.c
</pre></li><li class="listitem"><p><span class="emphasis"><em>Edit the Files:</em></span>
Make the changes to the temporary source code.</p></li><li class="listitem"><p><span class="emphasis"><em>Test Your Changes:</em></span>
Once you have modified the source code, the easiest way to test your changes
is by calling the <code class="filename">compile</code> task as shown in the following example:
</p><pre class="literallayout">
$ bitbake -c compile -f &lt;name_of_package&gt;
</pre><p>
The <code class="filename">-f</code> or <code class="filename">--force</code>
option forces re-execution of the specified task.
If you find problems with your code, you can just keep editing and
re-testing iteratively until things work as expected.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>All the modifications you make to the temporary source code
disappear once you <code class="filename">-c clean</code> or
<code class="filename">-c cleanall</code> with BitBake for the package.
Modifications will also disappear if you use the <code class="filename">rm_work</code>
feature as described in the
"<a class="link" href="#building-image" target="_top">Building an Image</a>"
section of the Yocto Project Quick Start.
</div></li><li class="listitem"><p><span class="emphasis"><em>Generate the Patch:</em></span>
Once your changes work as expected, you need to use Quilt to generate the final patch that
contains all your modifications.
</p><pre class="literallayout">
$ quilt refresh
</pre><p>
At this point the <code class="filename">my_changes.patch</code> file has all your edits made
to the <code class="filename">file1.c</code>, <code class="filename">file2.c</code>, and
<code class="filename">file3.c</code> files.</p><p>You can find the resulting patch file in the <code class="filename">patches/</code>
subdirectory of the source (<code class="filename">S</code>) directory.</p></li><li class="listitem"><p><span class="emphasis"><em>Copy the Patch File:</em></span>
For simplicity, copy the patch file into a directory named <code class="filename">files</code>,
which you can create in the same directory as the recipe.
Placing the patch here guarantees that the OpenEmbedded build system will find
the patch.
Next, add the patch into the
<code class="filename"><a class="link" href="#var-SRC_URI" target="_top">SRC_URI</a></code>
of the recipe.
Here is an example:
</p><pre class="literallayout">
SRC_URI += "file://my_changes.patch"
</pre></li><li class="listitem"><p><span class="emphasis"><em>Increment the Package Revision Number:</em></span>
Finally, don't forget to 'bump' the
<code class="filename"><a class="link" href="#var-PR" target="_top">PR</a></code>
value in the same recipe since the resulting packages have changed.</p></li></ol></div><p>
</p></div><div class="section" title="5.3.3. Using a Git Workflow"><div class="titlepage"><div><div><h3 class="title"><a id="using-a-git-workflow"></a>5.3.3. Using a Git Workflow</h3></div></div></div><p>
Git is an even more powerful tool that allows you to capture source code changes without having
a clean source tree.
This section outlines the typical workflow you can use to modify temporary source code,
test changes, and then preserve the changes in the form of a patch all using Git.
For general information on Git as it is used in the Yocto Project, see the
"<a class="link" href="#git" title="3.6. Git">Git</a>" section.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
This workflow uses Git only for its ability to manage local changes to the source code
and produce patches independent of any version control system used with the Yocto Project.
</div><p>
Follow these general steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p><span class="emphasis"><em>Find the Source Code:</em></span>
The temporary source code used by the OpenEmbedded build system is kept in the
build directory.
See the
"<a class="link" href="#finding-the-temporary-source-code" title="5.3.1. Finding the Temporary Source Code">Finding the Temporary Source Code</a>"
section to learn how to locate the directory that has the temporary source code for a
particular package.</p></li><li class="listitem"><p><span class="emphasis"><em>Change Your Working Directory:</em></span>
You need to be in the directory that has the temporary source code.
That directory is defined by the
<a class="link" href="#var-S" target="_top">S</a>
variable.</p></li><li class="listitem"><p><span class="emphasis"><em>Initialize a Git Repository:</em></span>
Use the <code class="filename">git init</code> command to initialize a new local repository
that is based on the work directory:
</p><pre class="literallayout">
$ git init
</pre></li><li class="listitem"><p><span class="emphasis"><em>Stage all the files:</em></span>
Use the <code class="filename">git add *</code> command to stage all the files in the source
code directory so that they can be committed:
</p><pre class="literallayout">
$ git add *
</pre></li><li class="listitem"><p><span class="emphasis"><em>Commit the Source Files:</em></span>
Use the <code class="filename">git commit</code> command to initially commit all the files in
the work directory:
</p><pre class="literallayout">
$ git commit
</pre><p>
At this point, your Git repository is aware of all the source code files.
Any edits you now make to files will be tracked by Git.</p></li><li class="listitem"><p><span class="emphasis"><em>Edit the Files:</em></span>
Make the changes to the temporary source code.</p></li><li class="listitem"><p><span class="emphasis"><em>Test Your Changes:</em></span>
Once you have modified the source code, the easiest way to test your changes
is by calling the <code class="filename">compile</code> task as shown in the following example:
</p><pre class="literallayout">
$ bitbake -c compile -f &lt;name_of_package&gt;
</pre><p>
The <code class="filename">-f</code> or <code class="filename">--force</code>
option forces re-execution of the specified task.
If you find problems with your code, you can just keep editing and
re-testing iteratively until things work as expected.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>All the modifications you make to the temporary source code
disappear once you <code class="filename">-c clean</code> or
<code class="filename">-c cleanall</code> with BitBake for the package.
Modifications will also disappear if you use the <code class="filename">rm_work</code>
feature as described in the
"<a class="link" href="#building-image" target="_top">Building an Image</a>"
section of the Yocto Project Quick Start.
</div></li><li class="listitem"><p><span class="emphasis"><em>See the List of Files You Changed:</em></span>
Use the <code class="filename">git status</code> command to see what files you have actually edited.
The ability to have Git track the files you have changed is an advantage that this
workflow has over the Quilt workflow.
Here is the Git command to list your changed files:
</p><pre class="literallayout">
$ git status
</pre></li><li class="listitem"><p><span class="emphasis"><em>Stage the Modified Files:</em></span>
Use the <code class="filename">git add</code> command to stage the changed files so they
can be committed as follows:
</p><pre class="literallayout">
$ git add file1.c file2.c file3.c
</pre></li><li class="listitem"><p><span class="emphasis"><em>Commit the Staged Files and View Your Changes:</em></span>
Use the <code class="filename">git commit</code> command to commit the changes to the
local repository.
Once you have committed the files, you can use the <code class="filename">git log</code>
command to see your changes:
</p><pre class="literallayout">
$ git commit
$ git log
</pre></li><li class="listitem"><p><span class="emphasis"><em>Generate the Patch:</em></span>
Once the changes are committed, use the <code class="filename">git format-patch</code>
command to generate a patch file:
</p><pre class="literallayout">
$ git format-patch HEAD~1
</pre><p>
The <code class="filename">HEAD~1</code> part of the command causes Git to generate the
patch file for the most recent commit.</p><p>At this point, the patch file has all your edits made
to the <code class="filename">file1.c</code>, <code class="filename">file2.c</code>, and
<code class="filename">file3.c</code> files.
You can find the resulting patch file in the current directory.
The patch file ends with <code class="filename">.patch</code>.</p></li><li class="listitem"><p><span class="emphasis"><em>Copy the Patch File:</em></span>
For simplicity, copy the patch file into a directory named <code class="filename">files</code>,
which you can create in the same directory as the recipe.
Placing the patch here guarantees that the OpenEmbedded build system will find
the patch.
Next, add the patch into the
<code class="filename"><a class="link" href="#var-SRC_URI" target="_top">SRC_URI</a></code>
of the recipe.
Here is an example:
</p><pre class="literallayout">
SRC_URI += "file://my_changes.patch"
</pre></li><li class="listitem"><p><span class="emphasis"><em>Increment the Package Revision Number:</em></span>
Finally, don't forget to 'bump' the
<code class="filename"><a class="link" href="#var-PR" target="_top">PR</a></code>
value in the same recipe since the resulting packages have changed.</p></li></ol></div><p>
</p></div></div><div class="section" title="5.4. Image Development Using Hob"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="image-development-using-hob"></a>5.4. Image Development Using Hob</h2></div></div></div><p>
The <a class="ulink" href="http://www.yoctoproject.org/projects/hob" target="_top">Hob</a> is a graphical user interface for the
OpenEmbedded build system, which is based on BitBake.
You can use the Hob to build custom operating system images within the Yocto Project build environment.
Hob simply provides a friendly interface over the build system used during system development.
In other words, building images with the Hob lets you take care of common build tasks more easily.
</p><p>
For a better understanding of Hob, see the project page at
<a class="ulink" href="http://www.yoctoproject.org/projects/hob" target="_top">http://www.yoctoproject.org/projects/hob</a> on the Yocto Project website.
The page has a short introductory training video on Hob.
The following lists some features of Hob:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>You can setup and run Hob using these commands:
</p><pre class="literallayout">
$ source oe-init-build-env
$ hob
</pre></li><li class="listitem"><p>You can set the
<a class="link" href="#var-MACHINE" target="_top"><code class="filename">MACHINE</code></a>
for which you are building the image.</p></li><li class="listitem"><p>You can modify various policy settings such as the package format used to build with,
the parrallelism BitBake uses, whether or not to build an external toolchain, and which host
to build against.</p></li><li class="listitem"><p>You can manage
<a class="link" href="#understanding-and-creating-layers" title="4.1. Understanding and Creating Layers">layers</a>.</p></li><li class="listitem"><p>You can select a base image and then add extra packages for your custom build.
</p></li><li class="listitem"><p>You can launch and monitor the build from within Hob.</p></li></ul></div><p>
</p></div><div class="section" title="5.5. Using a Development Shell"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="platdev-appdev-devshell"></a>5.5. Using a Development Shell</h2></div></div></div><p>
When debugging certain commands or even when just editing packages,
<code class="filename">devshell</code> can be a useful tool.
When you invoke <code class="filename">devshell</code>, source files are
extracted into your working directory and patches are applied.
Then, a new terminal is opened and you are placed in the working directory.
In the new terminal, all the OpenEmbedded build-related environment variables are
still defined so you can use commands such as <code class="filename">configure</code> and
<code class="filename">make</code>.
The commands execute just as if the OpenEmbedded build system were executing them.
Consequently, working this way can be helpful when debugging a build or preparing
software to be used with the OpenEmbedded build system.
</p><p>
Following is an example that uses <code class="filename">devshell</code> on a target named
<code class="filename">matchbox-desktop</code>:
</p><pre class="literallayout">
$ bitbake matchbox-desktop -c devshell
</pre><p>
</p><p>
This command opens a terminal with a shell prompt within the OpenEmbedded build environment.
The default shell is xterm.
The following occurs:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>The <code class="filename">PATH</code> variable includes the
cross-toolchain.</p></li><li class="listitem"><p>The <code class="filename">pkgconfig</code> variables find the correct
<code class="filename">.pc</code> files.</p></li><li class="listitem"><p>The <code class="filename">configure</code> command finds the
Yocto Project site files as well as any other necessary files.</p></li></ul></div><p>
Within this environment, you can run <code class="filename">configure</code>
or <code class="filename">compile</code> commands as if they were being run by
the OpenEmbedded build system itself.
As noted earlier, the working directory also automatically changes to the
source directory (<a class="link" href="#var-S" target="_top"><code class="filename">S</code></a>).
</p><p>
When you are finished, you just exit the shell or close the terminal window.
</p><p>
Because an external shell is launched rather than opening directly into the
original terminal window, it allows easier interaction with BitBake's multiple
threads as well as accomodates a future client/server split.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
It is worth remembering that when using <code class="filename">devshell</code>
you need to use the full compiler name such as <code class="filename">arm-poky-linux-gnueabi-gcc</code>
instead of just using <code class="filename">gcc</code>.
The same applies to other applications such as <code class="filename">binutils</code>,
<code class="filename">libtool</code> and so forth.
BitBake sets up environment variables such as <code class="filename">CC</code>
to assist applications, such as <code class="filename">make</code> to find the correct tools.
</p><p>
It is also worth noting that <code class="filename">devshell</code> still works over
X11 forwarding and similar situations
</p></div></div></div>
<div class="appendix" title="Appendix A. BSP Development Example"><div class="titlepage"><div><div><h2 class="title"><a id="dev-manual-bsp-appendix"></a>Appendix A. BSP Development Example</h2></div></div></div><p>
This appendix provides a complete BSP development example.
The example assumes the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>No previous preparation or use of the Yocto Project.</p></li><li class="listitem"><p>Use of the Crown Bay Board Support Package (BSP) as a "base" BSP from
which to work.
The example begins with the Crown Bay BSP as the starting point
but ends by building a new 'atom-pc' BSP, which was based on the Crown Bay BSP.
</p></li><li class="listitem"><p>Shell commands assume <code class="filename">bash</code></p></li><li class="listitem"><p>Example was developed on an Intel-based Core i7 platform running
Ubuntu 10.04 LTS released in April of 2010.</p></li></ul></div><p>
</p><div class="section" title="A.1. Getting Local Source Files and BSP Files"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="getting-local-yocto-project-files-and-bsp-files"></a>A.1. Getting Local Source Files and BSP Files</h2></div></div></div><p>
You need to have the <a class="link" href="#source-directory">source directory</a>
available on your host system.
You can set up this directory through tarball extraction or by cloning the
<code class="filename">poky</code> Git repository.
The following paragraphs describe both methods.
For additional information, see the bulleted item
"<a class="link" href="#local-yp-release">Yocto Project Release</a>".
</p><p>
As mentioned, one way to set up the source directory is to use Git to clone the
<code class="filename">poky</code> repository.
These commands create a local copy of the Git repository.
By default, the top-level directory of the repository is named <code class="filename">poky</code>:
</p><pre class="literallayout">
$ git clone git://git.yoctoproject.org/poky
$ cd poky
</pre><p>
Alternatively, you can start with the downloaded Poky "1.2+snapshot" tarball.
These commands unpack the tarball into a source directory structure.
By default, the top-level directory of the source directory is named
<code class="filename">poky-1.2+snapshot-8.0</code>:
</p><pre class="literallayout">
$ tar xfj poky-1.2+snapshot-8.0.tar.bz2
$ cd poky-1.2+snapshot-8.0
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>If you're using the tarball method, you can ignore all the following steps that
ask you to carry out Git operations.
You already have the results of those operations
in the form of the 1.2+snapshot release tarballs.
Consequently, there is nothing left to do other than extract those tarballs into the
proper locations.</p><p>Once you expand the released tarball, you have a snapshot of the Git repository
that represents a specific release.
Fundamentally, this is different than having a local copy of the Poky Git repository.
Given the tarball method, changes you make are building on top of a release.
With the Git repository method you have the ability to track development
and keep changes in revision control.
See the
"<a class="link" href="#repositories-tags-and-branches" title="3.6.1. Repositories, Tags, and Branches">Repositories, Tags, and Branches</a>" section
for more discussion around these differences.</p></div><p>
</p><p>
With the local <code class="filename">poky</code> Git repository set up,
you have all the development branches available to you from which you can work.
Next, you need to be sure that your local repository reflects the exact
release in which you are interested.
From inside the repository you can see the development branches that represent
areas of development that have diverged from the main (master) branch
at some point, such as a branch to track a maintenance release's development.
You can also see the tag names used to mark snapshots of stable releases or
points in the repository.
Use the following commands to list out the branches and the tags in the repository,
respectively.
</p><pre class="literallayout">
$ git branch -a
$ git tag -l
</pre><p>
For this example, we are going to use the Yocto Project 1.3 Release, which is code
named "1.2+snapshot".
To make sure we have a local area (branch in Git terms) on our machine that
reflects the 1.3 release, we can use the following commands:
</p><pre class="literallayout">
$ cd ~/poky
$ git fetch --tags
$ git checkout 1.2+snapshot-8.0 -b 1.2+snapshot
Switched to a new branch '1.2+snapshot'
</pre><p>
The <code class="filename">git fetch --tags</code> is somewhat redundant since you just set
up the repository and should have all the tags.
The <code class="filename">fetch</code> command makes sure all the tags are available in your
local repository.
The Git <code class="filename">checkout</code> command with the <code class="filename">-b</code> option
creates a local branch for you named <code class="filename">1.2+snapshot</code>.
Your local branch begins in the same state as the Yocto Project 1.3 released tarball
marked with the <code class="filename">1.2+snapshot-8.0</code> tag in the source repositories.
</p></div><div class="section" title="A.2. Choosing a Base BSP"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="choosing-a-base-bsp-app"></a>A.2. Choosing a Base BSP</h2></div></div></div><p>
For this example, the base BSP is the <span class="trademark">Intel</span>®
<span class="trademark">Atom</span>™ Processor E660 with Intel Platform
Controller Hub EG20T Development Kit, which is otherwise referred to as "Crown Bay."
The BSP layer is <code class="filename">meta-crownbay</code>.
The base BSP is simply the BSP
we will be using as a starting point, so don't worry if you don't actually have Crown Bay
hardware.
The remainder of the example transforms the base BSP into a BSP that should be
able to boot on generic atom-pc (netbook) hardware.
</p><p>
For information on how to choose a base BSP, see
"<a class="link" href="#developing-a-board-support-package-bsp" title="5.1.1. Developing a Board Support Package (BSP)">Developing a Board Support Package (BSP)</a>".
</p></div><div class="section" title="A.3. Getting Your Base BSP"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="getting-your-base-bsp-app"></a>A.3. Getting Your Base BSP</h2></div></div></div><p>
You need to have the base BSP layer on your development system.
Similar to the local <a class="link" href="#source-directory">source directory</a>,
you can get the BSP
layer in a couple of different ways:
download the BSP tarball and extract it, or set up a local Git repository that
has the BSP layers.
You should use the same method that you used to set up the source directory earlier.
See "<a class="link" href="#getting-setup" title="2.2. Getting Set Up">Getting Setup</a>" for information on how to get
the BSP files.
</p><p>
This example assumes the BSP layer will be located within a directory named
<code class="filename">meta-intel</code> contained within the <code class="filename">poky</code>
parent directory.
The following steps will automatically create the
<code class="filename">meta-intel</code> directory and the contained
<code class="filename">meta-crownbay</code> starting point in both the Git and the tarball cases.
</p><p>
If you're using the Git method, you could do the following to create
the starting layout after you have made sure you are in the <code class="filename">poky</code>
directory created in the previous steps:
</p><pre class="literallayout">
$ git clone git://git.yoctoproject.org/meta-intel.git
$ cd meta-intel
</pre><p>
Alternatively, you can start with the downloaded Crown Bay tarball.
You can download the 1.2+snapshot version of the BSP tarball from the
<a class="ulink" href="http://www.yoctoproject.org/download" target="_top">Download</a> page of the
Yocto Project website.
Here is the specific link for the tarball needed for this example:
<a class="ulink" href="http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/machines/crownbay-noemgd/crownbay-noemgd-1.2+snapshot-8.0.tar.bz2" target="_top">http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/machines/crownbay-noemgd/crownbay-noemgd-1.2+snapshot-8.0.tar.bz2</a>.
Again, be sure that you are already in the <code class="filename">poky</code> directory
as described previously before installing the tarball:
</p><pre class="literallayout">
$ tar xfj crownbay-noemgd-1.2+snapshot-8.0.tar.bz2
$ cd meta-intel
</pre><p>
</p><p>
The <code class="filename">meta-intel</code> directory contains all the metadata
that supports BSP creation.
If you're using the Git method, the following
step will switch to the 1.2+snapshot metadata.
If you're using the tarball method, you already have the correct metadata and can
skip to the next step.
Because <code class="filename">meta-intel</code> is its own Git repository, you will want
to be sure you are in the appropriate branch for your work.
For this example we are going to use the <code class="filename">1.2+snapshot</code> branch.
</p><pre class="literallayout">
$ git checkout -b 1.2+snapshot origin/1.2+snapshot
Branch 1.2+snapshot set up to track remote branch 1.2+snapshot from origin.
Switched to a new branch '1.2+snapshot'
</pre><p>
</p></div><div class="section" title="A.4. Making a Copy of the Base BSP to Create Your New BSP Layer"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="making-a-copy-of-the-base bsp-to-create-your-new-bsp-layer-app"></a>A.4. Making a Copy of the Base BSP to Create Your New BSP Layer</h2></div></div></div><p>
Now that you have set up the source directory and included the base BSP files, you need to
create a new layer for your BSP.
To create your BSP layer, you simply copy the <code class="filename">meta-crownbay</code>
layer to a new layer.
</p><p>
For this example, the new layer will be named <code class="filename">meta-mymachine</code>.
The name should follow the BSP layer naming convention, which is
<code class="filename">meta-&lt;name&gt;</code>.
The following assumes your working directory is <code class="filename">meta-intel</code>
inside your source directory.
To start your new layer, just copy the new layer alongside the existing
BSP layers in the <code class="filename">meta-intel</code> directory:
</p><pre class="literallayout">
$ cp -a meta-crownbay/ meta-mymachine
</pre><p>
</p></div><div class="section" title="A.5. Making Changes to Your BSP"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="making-changes-to-your-bsp-app"></a>A.5. Making Changes to Your BSP</h2></div></div></div><p>
Right now you have two identical BSP layers with different names:
<code class="filename">meta-crownbay</code> and <code class="filename">meta-mymachine</code>.
You need to change your configurations so that they work for your new BSP and
your particular hardware.
The following sections look at each of these areas of the BSP.
</p><div class="section" title="A.5.1. Changing the BSP Configuration"><div class="titlepage"><div><div><h3 class="title"><a id="changing-the-bsp-configuration"></a>A.5.1. Changing the BSP Configuration</h3></div></div></div><p>
We will look first at the configurations, which are all done in the layer’s
<code class="filename">conf</code> directory.
</p><p>
First, since in this example the new BSP will not support EMGD, we will get rid of the
<code class="filename">crownbay.conf</code> file and then rename the
<code class="filename">crownbay-noemgd.conf</code> file to <code class="filename">mymachine.conf</code>.
Much of what we do in the configuration directory is designed to help the OpenEmbedded
build system work with the new layer and to be able to find and use the right software.
The following two commands result in a single machine configuration file named
<code class="filename">mymachine.conf</code>.
</p><pre class="literallayout">
$ rm meta-mymachine/conf/machine/crownbay.conf
$ mv meta-mymachine/conf/machine/crownbay-noemgd.conf \
meta-mymachine/conf/machine/mymachine.conf
</pre><p>
</p><p>
Next, we need to make changes to the <code class="filename">mymachine.conf</code> itself.
The only changes we want to make for this example are to the comment lines.
Changing comments, of course, is never strictly necessary, but it's alway good form to make
them reflect reality as much as possible.
Here, simply substitute the Crown Bay name with an appropriate name for the BSP
(<code class="filename">mymachine</code> in this case) and change the description to
something that describes your hardware.
</p><p>
Note that inside the <code class="filename">mymachine.conf</code> is the
<code class="filename">PREFERRED_VERSION_linux-yocto</code> statement.
This statement identifies the kernel that the BSP is going to use.
In this case, the BSP is using <code class="filename">linux-yocto</code>, which is the
current Yocto Project kernel based on the Linux 3.2 release.
</p><p>
The next configuration file in the new BSP layer we need to edit is
<code class="filename">meta-mymachine/conf/layer.conf</code>.
This file identifies build information needed for the new layer.
You can see the
"<a class="link" href="#bsp-filelayout-layer" target="_top">Layer Configuration File</a>" section
in The Board Support Packages (BSP) Development Guide for more information on this configuration file.
Basically, we are changing the existing statements to work with our BSP.
</p><p>
The file contains these statements that reference the Crown Bay BSP:
</p><pre class="literallayout">
BBFILE_COLLECTIONS += "crownbay"
BBFILE_PATTERN_crownbay := "^${LAYERDIR}/"
BBFILE_PRIORITY_crownbay = "6"
LAYERDEPENDS_crownbay = "intel"
</pre><p>
</p><p>
Simply substitute the machine string name <code class="filename">crownbay</code>
with the new machine name <code class="filename">mymachine</code> to get the following:
</p><pre class="literallayout">
BBFILE_COLLECTIONS += "mymachine"
BBFILE_PATTERN_mymachine := "^${LAYERDIR}/"
BBFILE_PRIORITY_mymachine = "6"
LAYERDEPENDS_mymachine = "intel"
</pre><p>
</p></div><div class="section" title="A.5.2. Changing the Recipes in Your BSP"><div class="titlepage"><div><div><h3 class="title"><a id="changing-the-recipes-in-your-bsp"></a>A.5.2. Changing the Recipes in Your BSP</h3></div></div></div><p>
Now we will take a look at the recipes in your new layer.
The standard BSP structure has areas for BSP, graphics, core, and kernel recipes.
When you create a BSP, you use these areas for appropriate recipes and append files.
Recipes take the form of <code class="filename">.bb</code> files, while append files take
the form of <code class="filename">.bbappend</code> files.
If you want to leverage the existing recipes the OpenEmbedded build system uses
but change those recipes, you can use <code class="filename">.bbappend</code> files.
All new recipes and append files for your layer must go in the layer’s
<code class="filename">recipes-bsp</code>, <code class="filename">recipes-kernel</code>,
<code class="filename">recipes-core</code>, and
<code class="filename">recipes-graphics</code> directories.
</p><div class="section" title="A.5.2.1. Changing  recipes-bsp"><div class="titlepage"><div><div><h4 class="title"><a id="changing-recipes-bsp"></a>A.5.2.1. Changing  <code class="filename">recipes-bsp</code></h4></div></div></div><p>
First, let's look at <code class="filename">recipes-bsp</code>.
For this example we are not adding any new BSP recipes.
And, we only need to remove the formfactor we do not want and change the name of
the remaining one that doesn't support EMGD.
These commands take care of the <code class="filename">recipes-bsp</code> recipes:
</p><pre class="literallayout">
$ rm -rf meta-mymachine/recipes-bsp/formfactor/formfactor/crownbay
$ mv meta-mymachine/recipes-bsp/formfactor/formfactor/crownbay-noemgd/ \
meta-mymachine/recipes-bsp/formfactor/formfactor/mymachine
</pre><p>
</p></div><div class="section" title="A.5.2.2. Changing  recipes-graphics"><div class="titlepage"><div><div><h4 class="title"><a id="changing-recipes-graphics"></a>A.5.2.2. Changing  <code class="filename">recipes-graphics</code></h4></div></div></div><p>
Now let's look at <code class="filename">recipes-graphics</code>.
For this example we want to remove anything that supports EMGD and
be sure to rename remaining directories appropriately.
The following commands clean up the <code class="filename">recipes-graphics</code> directory:
</p><pre class="literallayout">
$ rm -rf meta-mymachine/recipes-graphics/xorg-xserver/xserver-xf86-config/crownbay
$ mv meta-mymachine/recipes-graphics/xorg-xserver/xserver-xf86-config/crownbay-noemgd \
meta-mymachine/recipes-graphics/xorg-xserver/xserver-xf86-config/mymachine
</pre><p>
</p><p>
At this point the <code class="filename">recipes-graphics</code> directory just has files that
support Video Electronics Standards Association (VESA) graphics modes and not EMGD.
</p></div><div class="section" title="A.5.2.3. Changing  recipes-core"><div class="titlepage"><div><div><h4 class="title"><a id="changing-recipes-core"></a>A.5.2.3. Changing  <code class="filename">recipes-core</code></h4></div></div></div><p>
Now let's look at changes in <code class="filename">recipes-core</code>.
The file <code class="filename">task-core-tools.bbappend</code> in
<code class="filename">recipes-core/tasks</code> appends the similarly named recipe
located in the <a class="link" href="#source-directory">source directory</a> at
<code class="filename">meta/recipes-core/tasks</code>.
The append file in our layer right now is Crown Bay-specific and supports
EMGD and non-EMGD.
Here are the contents of the file:
</p><pre class="literallayout">
RRECOMMENDS_task-core-tools-profile_append_crownbay = " systemtap"
RRECOMMENDS_task-core-tools-profile_append_crownbay-noemgd = " systemtap"
</pre><p>
</p><p>
The <code class="filename">RRECOMMENDS</code> statements list packages that
extend usability.
The first <code class="filename">RRECOMMENDS</code> statement can be removed, while the
second one can be changed to reflect <code class="filename">meta-mymachine</code>:
</p><pre class="literallayout">
RRECOMMENDS_task-core-tools-profile_append_mymachine = " systemtap"
</pre><p>
</p></div><div class="section" title="A.5.2.4. Changing  recipes-kernel"><div class="titlepage"><div><div><h4 class="title"><a id="changing-recipes-kernel"></a>A.5.2.4. Changing  <code class="filename">recipes-kernel</code></h4></div></div></div><p>
Finally, let's look at <code class="filename">recipes-kernel</code> changes.
Recall that the BSP uses the <code class="filename">linux-yocto</code> kernel as determined
earlier in the <code class="filename">mymachine.conf</code>.
The recipe for that kernel is not located in the
BSP layer but rather in the source directory at
<code class="filename">meta/recipes-kernel/linux</code> and is
named <code class="filename">linux-yocto_3.2.bb</code>.
The <code class="filename">SRCREV_machine</code> and <code class="filename">SRCREV_meta</code>
statements point to the exact commits used by the Yocto Project development team
in their source repositories that identify the right kernel for our hardware.
In other words, the <code class="filename">SRCREV</code> values are simply Git commit
IDs that identify which commit on each
of the kernel branches (machine and meta) will be checked out and used to build
the kernel.
</p><p>
However, in the <code class="filename">meta-mymachine</code> layer in
<code class="filename">recipes-kernel/linux</code> resides a <code class="filename">.bbappend</code>
file named <code class="filename">linux-yocto_3.2.bbappend</code> that
appends information to the recipe of the same name in <code class="filename">meta/recipes-kernel/linux</code>.
Thus, the <code class="filename">SRCREV</code> statements in the append file override
the more general statements found in <code class="filename">meta</code>.
</p><p>
The <code class="filename">SRCREV</code> statements in the append file currently identify
the kernel that supports the Crown Bay BSP with and without EMGD support.
Here are the statements:
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>The commit ID strings used in this manual might not match the actual commit
ID strings found in the <code class="filename">linux-yocto_3.2.bbappend</code> file.
For the example, this difference does not matter.</div><p>
</p><pre class="literallayout">
SRCREV_machine_pn-linux-yocto_crownbay ?= \
"211fc7f4d10ec2b82b424286aabbaff9254b7cbd"
SRCREV_meta_pn-linux-yocto_crownbay ?= \
"514847185c78c07f52e02750fbe0a03ca3a31d8f"
SRCREV_machine_pn-linux-yocto_crownbay-noemgd ?= \
"211fc7f4d10ec2b82b424286aabbaff9254b7cbd"
SRCREV_meta_pn-linux-yocto_crownbay-noemgd ?= \
"514847185c78c07f52e02750fbe0a03ca3a31d8f"
</pre><p>
</p><p>
You will notice that there are two pairs of <code class="filename">SRCREV</code> statements.
The top pair identifies the kernel that supports
EMGD, which we don’t care about in this example.
The bottom pair identifies the kernel that we will use:
<code class="filename">linux-yocto</code>.
At this point though, the unique commit strings all are still associated with
Crown Bay and not <code class="filename">meta-mymachine</code>.
</p><p>
To fix this situation in <code class="filename">linux-yocto_3.2.bbappend</code>,
we delete the two <code class="filename">SRCREV</code> statements that support
EMGD (the top pair).
We also change the remaining pair to specify <code class="filename">mymachine</code>
and insert the commit identifiers to identify the kernel in which we
are interested, which will be based on the <code class="filename">atom-pc-standard</code>
kernel.
In this case, because we're working with the 1.2+snapshot branch of everything, we
need to use the <code class="filename">SRCREV</code> values for the atom-pc branch
that are associated with the 1.2+snapshot release.
To find those values, we need to find the <code class="filename">SRCREV</code>
values that 1.2+snapshot uses for the atom-pc branch, which we find in the
<code class="filename">poky/meta-yocto/recipes-kernel/linux/linux-yocto_3.2.bbappend</code>
file.
</p><p>
The machine <code class="filename">SRCREV</code> we want is in the
<code class="filename">SRCREV_machine_atom-pc</code> variable.
The meta <code class="filename">SRCREV</code> isn't specified in this file, so it must be
specified in the base kernel recipe in the
<code class="filename">poky/meta/recipes-kernel/linux/linux-yocto_3.2.bb</code>
file, in the <code class="filename">SRCREV_meta</code> variable found there.
Here are the final <code class="filename">SRCREV</code> statements:
</p><pre class="literallayout">
SRCREV_machine_pn-linux-yocto_mymachine ?= \
"f29531a41df15d74be5ad47d958e4117ca9e489e"
SRCREV_meta_pn-linux-yocto_mymachine ?= \
"b14a08f5c7b469a5077c10942f4e1aec171faa9d"
</pre><p>
</p><p>
In this example, we're using the <code class="filename">SRCREV</code> values we
found already captured in the 1.2+snapshot release because we're creating a BSP based on
1.2+snapshot.
If, instead, we had based our BSP on the master branches, we would want to use
the most recent <code class="filename">SRCREV</code> values taken directly from the kernel repo.
We will not be doing that for this example.
However, if you do base a future BSP on master and
if you are familiar with Git repositories, you probably won’t have trouble locating the
exact commit strings in the Yocto Project source repositories you need to change
the <code class="filename">SRCREV</code> statements.
You can find all the <code class="filename">machine</code> and <code class="filename">meta</code>
branch points (commits) for the <code class="filename">linux-yocto-3.2</code> kernel at
<a class="ulink" href="http://git.yoctoproject.org/cgit/cgit.cgi/linux-yocto-3.2" target="_top">http://git.yoctoproject.org/cgit/cgit.cgi/linux-yocto-3.2</a>.
</p><p>
If you need a little more assistance after going to the link then do the following:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Expand the list of branches by clicking <code class="filename">[…]</code></p></li><li class="listitem"><p>Click on the <code class="filename">standard/default/common-pc/atom-pc</code>
branch</p></li><li class="listitem"><p>Click on the commit column header to view the top commit</p></li><li class="listitem"><p>Copy the commit string for use in the
<code class="filename">linux-yocto_3.2.bbappend</code> file</p></li></ol></div><p>
</p><p>
For the <code class="filename">SRCREV</code> statement that points to the <code class="filename">meta</code>
branch use the same procedure except expand the <code class="filename">meta</code>
branch in step 2 above.
</p><p>
Also in the <code class="filename">linux-yocto_3.2.bbappend</code> file are
<a class="link" href="#var-COMPATIBLE_MACHINE" target="_top"><code class="filename">COMPATIBLE_MACHINE</code></a>,
<a class="link" href="#var-KMACHINE" target="_top"><code class="filename">KMACHINE</code></a>,
and
<a class="link" href="#var-KBRANCH" target="_top"><code class="filename">KBRANCH</code></a> statements.
Two sets of these exist: one set supports EMGD and one set does not.
Because we are not interested in supporting EMGD those three can be deleted.
The remaining three must be changed so that <code class="filename">mymachine</code> replaces
<code class="filename">crownbay-noemgd</code> and <code class="filename">crownbay</code>.
Because we are using the <code class="filename">atom-pc</code> branch for this new BSP, we can also find
the exact branch we need for the <code class="filename">KMACHINE</code>
and <code class="filename">KBRANCH</code> variables in our new BSP from the value
we find in the
<code class="filename">poky/meta-yocto/recipes-kernel/linux/linux-yocto_3.2.bbappend</code>
file we looked at in a previous step.
In this case, the values we want are in the <code class="filename">KMACHINE_atom-pc</code> variable
and the <code class="filename">KBRANCH_atom-pc</code> variables in that file.
Here is the final <code class="filename">linux-yocto_3.2.bbappend</code> file after all
the edits:
</p><pre class="literallayout">
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
COMPATIBLE_MACHINE_mymachine = "mymachine"
KMACHINE_mymachine = "atom-pc"
KBRANCH_mymachine = "standard/default/common-pc/atom-pc"
SRCREV_machine_pn-linux-yocto_mymachine ?= \
"f29531a41df15d74be5ad47d958e4117ca9e489e"
SRCREV_meta_pn-linux-yocto_mymachine ?= \
"b14a08f5c7b469a5077c10942f4e1aec171faa9d"
</pre><p>
</p></div></div><div class="section" title="A.5.3. BSP Recipe Change Summary"><div class="titlepage"><div><div><h3 class="title"><a id="bsp-recipe-change-summary"></a>A.5.3. BSP Recipe Change Summary</h3></div></div></div><p>
In summary, the edits to the layer’s recipe files result in removal of any files and
statements that do not support your targeted hardware in addition to the inclusion
of any new recipes you might need.
In this example, it was simply a matter of ridding the new layer
<code class="filename">meta-mymachine</code> of any code that supported the EMGD features
and making sure we were identifying the kernel that supports our example, which
is the <code class="filename">atom-pc-standard</code> kernel.
We did not introduce any new recipes to the layer.
</p><p>
Finally, it is also important to update the layer’s <code class="filename">README</code>
file so that the information in it reflects your BSP.
</p></div></div><div class="section" title="A.6. Preparing for the Build"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="preparing-for-the-build-app"></a>A.6. Preparing for the Build</h2></div></div></div><p>
To get ready to build your image that uses the new layer you need to do the following:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Get the environment ready for the build by sourcing the environment
script.
The environment script is in the top-level of the source directory.
The script has the string
<code class="filename">init-build-env</code> in the file’s name.
For this example, the following command gets the build environment ready:
</p><pre class="literallayout">
$ source oe-init-build-env yocto-build
</pre><p>
When you source the script, a build directory is created in the current
working directory.
In our example we were in the <code class="filename">poky</code> directory.
Thus, entering the previous command created the <code class="filename">yocto-build</code> directory.
If you do not provide a name for the build directory it defaults to
<code class="filename">build</code>.
The <code class="filename">yocto-build</code> directory contains a
<code class="filename">conf</code> directory that has
two configuration files you will need to check: <code class="filename">bblayers.conf</code>
and <code class="filename">local.conf</code>.</p></li><li class="listitem"><p>Check and edit the resulting <code class="filename">local.conf</code> file.
This file minimally identifies the machine for which to build the image by
configuring the <code class="filename">MACHINE</code> variable.
For this example you must set the variable to mymachine as follows:
</p><pre class="literallayout">
MACHINE ??= “mymachine”
</pre><p>
You should also be sure any other variables in which you are interested are set.
Some variables to consider are <code class="filename">BB_NUMBER_THREADS</code>
and <code class="filename">PARALLEL_MAKE</code>, both of which can greatly reduce your build time
if your development system supports multiple cores.
For development systems that support multiple cores, a good rule of thumb is to set
both the <code class="filename">BB_NUMBER_THREADS</code> and <code class="filename">PARALLEL_MAKE</code>
variables to twice the number of cores your system supports.</p></li><li class="listitem"><p>Update the <code class="filename">bblayers.conf</code> file so that it includes
both the path to your new BSP layer and the path to the
<code class="filename">meta-intel</code> layer.
In this example, you need to include both these paths as part of the
<code class="filename">BBLAYERS</code> variable:
</p><pre class="literallayout">
$HOME/poky/meta-intel
$HOME/poky/meta-intel/meta-mymachine
</pre></li></ol></div><p>
</p><p>
The
<a class="link" href="#ref-variables-glos" target="_top">Variables Glossary</a> chapter in the
Yocto Project Reference Manual has more information on configuration variables.
</p></div><div class="section" title="A.7. Building and Booting the Image"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="building-the-image-app"></a>A.7. Building and Booting the Image</h2></div></div></div><p>
To build the image for our <code class="filename">meta-mymachine</code> BSP enter the following command
from the same shell from which you ran the setup script.
You should run the <code class="filename">bitbake</code> command without any intervening shell commands.
For example, moving your working directory around could cause problems.
Here is the command for this example:
</p><pre class="literallayout">
$ bitbake -k core-image-sato
</pre><p>
</p><p>
This command specifies an image that has Sato support and that can be run from a USB device or
from a CD without having to first install anything.
The build process takes significant time and includes thousands of tasks, which are reported
at the console.
If the build results in any type of error you should check for misspellings in the
files you changed or problems with your host development environment such as missing packages.
</p><p>
Finally, once you have an image, you can try booting it from a device
(e.g. a USB device).
To prepare a bootable USB device, insert a USB flash drive into your build system and
copy the <code class="filename">.hddimg</code> file, located in the
<code class="filename">poky/build/tmp/deploy/images</code>
directory after a successful build to the flash drive.
Assuming the USB flash drive takes device <code class="filename">/dev/sdf</code>,
use <code class="filename">dd</code> to copy the live image to it.
For example:
</p><pre class="literallayout">
# dd if=core-image-sato-mymachine-20111101223904.hddimg of=/dev/sdf
# sync
# eject /dev/sdf
</pre><p>
You should now have a bootable USB flash device.
</p><p>
Insert the device
into a bootable USB socket on the target, and power it on.
The system should boot to the Sato graphical desktop.
<sup>[<a id="id1497755" href="#ftn.id1497755" class="footnote">2</a>]</sup>
</p><p>
For reference, the sato image produced by the previous steps for 1.2+snapshot
should look like the following in terms of size.
If your sato image is much different from this,
you probably made a mistake in one of the above steps:
</p><pre class="literallayout">
260538368 2012-04-27 01:44 core-image-sato-mymachine-20120427025051.hddimg
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>The previous instructions are also present in the README that was copied
from meta-crownbay, which should also be updated to reflect the specifics of your
new BSP.
That file and the <code class="filename">README.hardware</code> file in the top-level
<code class="filename">poky</code> directory
also provides some suggestions for things to try if booting fails and produces
strange error messages.</div><p>
</p></div><div class="footnotes"><br /><hr width="100" align="left" /><div class="footnote"><p><sup>[<a id="ftn.id1497755" href="#id1497755" class="para">2</a>] </sup>Because
this new image is not in any way tailored to the system you're
booting it on, which is assumed to be some sort of atom-pc (netbook) system for this
example, it might not be completely functional though it should at least boot to a text
prompt.
Specifically, it might fail to boot into graphics without some tweaking.
If this ends up being the case, a possible next step would be to replace the
<code class="filename">mymachine.conf</code>
contents with the contents of <code class="filename">atom-pc.conf</code> and replace
<code class="filename">xorg.conf</code> with <code class="filename">atom-pc xorg.conf</code>
in <code class="filename">meta-yocto</code> and see if it fares any better.
In any case, following the previous steps will give you a buildable image that
will probably boot on most systems.
Getting things working like you want
them to for your hardware will normally require some amount of experimentation with
configuration settings.</p></div></div></div>
<div class="appendix" title="Appendix B. Kernel Modification Example"><div class="titlepage"><div><div><h2 class="title"><a id="dev-manual-kernel-appendix"></a>Appendix B. Kernel Modification Example</h2></div></div></div><p>
Kernel modification involves changing or adding configurations to an existing kernel,
changing or adding recipes to the kernel that are needed to support specific hardware features,
or even altering the source code itself.
This appendix presents simple examples that modify the kernel source code,
change the kernel configuration, and add a kernel source recipe.
</p><div class="section" title="B.1. Modifying the Kernel Source Code"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="modifying-the-kernel-source-code"></a>B.1. Modifying the Kernel Source Code</h2></div></div></div><p>
This example adds some simple QEMU emulator console output at boot time by
adding <code class="filename">printk</code> statements to the kernel's
<code class="filename">calibrate.c</code> source code file.
Booting the modified image causes the added messages to appear on the emulator's
console.
</p><div class="section" title="B.1.1. Understanding the Files You Need"><div class="titlepage"><div><div><h3 class="title"><a id="understanding-the-files-you-need"></a>B.1.1. Understanding the Files You Need</h3></div></div></div><p>
Before you modify the kernel, you need to know what Git repositories and file
structures you need.
Briefly, you need the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>A local
<a class="link" href="#source-directory">source directory</a> for the
poky Git repository</p></li><li class="listitem"><p>Local copies of the
<a class="link" href="#poky-extras-repo"><code class="filename">poky-extras</code></a>
Git repository placed within the source directory.</p></li><li class="listitem"><p>A bare clone of the
<a class="link" href="#local-kernel-files">Yocto Project Kernel</a> upstream Git
repository to which you want to push your modifications.
</p></li><li class="listitem"><p>A copy of that bare clone in which you make your source
modifications</p></li></ul></div><p>
</p><p>
The following figure summarizes these four areas.
Within each rectangular that represents a data structure, a
host development directory pathname appears at the
lower left-hand corner of the box.
These pathnames are the locations used in this example.
The figure also provides key statements and commands used during the kernel
modification process:
</p><p>
</p><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="630"><tr style="height: 450px"><td align="center"><img src="figures/kernel-example-repos-denzil.png" align="middle" /></td></tr></table><p>
</p><p>
Here is a brief description of the four areas:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Local Source Directory:</em></span>
This area contains all the metadata that supports building images
using the OpenEmbedded build system.
In this example, the source directory also
contains the build directory, which contains the configuration directory
that lets you control the build.
Also in this example, the source directory contains local copies of the
<code class="filename">poky-extras</code> Git repository.</p><p>See the bulleted item
"<a class="link" href="#local-yp-release">Yocto Project Release</a>"
for information on how to get these files on your local system.</p></li><li class="listitem"><p><span class="emphasis"><em>Local copies of the<code class="filename">poky-extras</code>
Git Repository:</em></span>
This area contains the <code class="filename">meta-kernel-dev</code> layer,
which is where you make changes that append the kernel build recipes.
You edit <code class="filename">.bbappend</code> files to locate your
local kernel source files and to identify the kernel being built.
This Git repository is a gathering place for extensions to the Yocto Project
(or really any) kernel recipes that faciliate the creation and development
of kernel features, BSPs or configurations.</p><p>See the bulleted item
"<a class="link" href="#poky-extras-repo">The
<code class="filename">poky-extras</code> Git Repository</a>"
for information on how to get these files.</p></li><li class="listitem"><p><span class="emphasis"><em>Bare Clone of the Yocto Project kernel:</em></span>
This bare Git repository tracks the upstream Git repository of the Linux
Yocto kernel source code you are changing.
When you modify the kernel you must work through a bare clone.
All source code changes you make to the kernel must be committed and
pushed to the bare clone using Git commands.
As mentioned, the <code class="filename">.bbappend</code> file in the
<code class="filename">poky-extras</code> repository points to the bare clone
so that the build process can locate the locally changed source files.</p><p>See the bulleted item
"<a class="link" href="#local-kernel-files">Yocto Project Kernel</a>"
for information on how to set up the bare clone.
</p></li><li class="listitem"><p><span class="emphasis"><em>Copy of the Yocto Project Kernel Bare Clone:</em></span>
This Git repository contains the actual source files that you modify.
Any changes you make to files in this location need to ultimately be pushed
to the bare clone using the <code class="filename">git push</code> command.</p><p>See the bulleted item
"<a class="link" href="#local-kernel-files">Yocto Project Kernel</a>"
for information on how to set up the bare clone.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>Typically, Git workflows follow a scheme where changes made to a local area
are pulled into a Git repository.
However, because the <code class="filename">git pull</code> command does not work
with bare clones, this workflow pushes changes to the
repository even though you could use other more complicated methods to
get changes into the bare clone.</div><p>
</p></li></ul></div><p>
</p></div><div class="section" title="B.1.2. Setting Up the Local Source Directory"><div class="titlepage"><div><div><h3 class="title"><a id="setting-up-the-local-yocto-project-files-git-repository"></a>B.1.2. Setting Up the Local Source Directory</h3></div></div></div><p>
You can set up the source directory through tarball extraction or by
cloning the <code class="filename">poky</code> Git repository.
This example uses <code class="filename">poky</code> as the root directory of the
local source directory.
See the bulleted item
"<a class="link" href="#local-yp-release">Yocto Project Release</a>"
for information on how to get these files.
</p><p>
Once you have source directory set up,
you have many development branches from which you can work.
From inside the local repository you can see the branch names and the tag names used
in the upstream Git repository by using either of the following commands:
</p><pre class="literallayout">
$ cd poky
$ git branch -a
$ git tag -l
</pre><p>
This example uses the Yocto Project 1.3 Release code named "1.2+snapshot",
which maps to the <code class="filename">1.2+snapshot</code> branch in the repository.
The following commands create and checkout the local <code class="filename">1.2+snapshot</code>
branch:
</p><pre class="literallayout">
$ git checkout -b 1.2+snapshot origin/1.2+snapshot
Branch 1.2+snapshot set up to track remote branch 1.2+snapshot from origin.
Switched to a new branch '1.2+snapshot'
</pre><p>
</p></div><div class="section" title="B.1.3. Setting Up the Local poky-extras Git Repository"><div class="titlepage"><div><div><h3 class="title"><a id="setting-up-the-poky-extras-git-repository"></a>B.1.3. Setting Up the Local poky-extras Git Repository</h3></div></div></div><p>
This example creates a local copy of the <code class="filename">poky-extras</code> Git
repository inside the <code class="filename">poky</code> source directory.
See the bulleted item "<a class="link" href="#poky-extras-repo">The
<code class="filename">poky-extras</code> Git Repository</a>"
for information on how to set up a local copy of the
<code class="filename">poky-extras</code> repository.
</p><p>
Because this example uses the Yocto Project 1.3 Release code
named "1.2+snapshot", which maps to the <code class="filename">1.2+snapshot</code>
branch in the repository, you need to be sure you are using that
branch for <code class="filename">poky-extra</code>.
The following commands create and checkout the local
branch you are using for the <code class="filename">1.2+snapshot</code>
branch:
</p><pre class="literallayout">
$ git checkout -b 1.2+snapshot origin/1.2+snapshot
Branch 1.2+snapshot set up to track remote branch 1.2+snapshot from origin.
Switched to a new branch '1.2+snapshot'
</pre><p>
</p></div><div class="section" title="B.1.4. Setting Up the Bare Clone and its Copy"><div class="titlepage"><div><div><h3 class="title"><a id="setting-up-the-bare-clone-and-its-copy"></a>B.1.4. Setting Up the Bare Clone and its Copy</h3></div></div></div><p>
This example modifies the <code class="filename">linux-yocto-3.2</code> kernel.
Thus, you need to create a bare clone of that kernel and then make a copy of the
bare clone.
See the bulleted item
"<a class="link" href="#local-kernel-files">Yocto Project Kernel</a>"
for information on how to do that.
</p><p>
The bare clone exists for the kernel build tools and simply as the receiving end
of <code class="filename">git push</code>
commands after you make edits and commits inside the copy of the clone.
The copy (<code class="filename">my-linux-yocto-3.2-work</code> in this example) has to have
a local branch created and checked out for your work.
This example uses <code class="filename">common-pc-base</code> as the local branch.
The following commands create and checkout the branch:
</p><pre class="literallayout">
$ cd ~/my-linux-yocto-3.2-work
$ git checkout -b common-pc-base origin/standard/default/common-pc/base
Checking out files: 100% (532/532), done.
Branch common-pc-base set up to track remote branch
standard/default/common-pc/base from origin.
Switched to a new branch 'common-pc-base'
</pre><p>
</p></div><div class="section" title="B.1.5. Building and Booting the Default QEMU Kernel Image"><div class="titlepage"><div><div><h3 class="title"><a id="building-and-booting-the-default-qemu-kernel-image"></a>B.1.5. Building and Booting the Default QEMU Kernel Image</h3></div></div></div><p>
Before we make changes to the kernel source files, this example first builds the
default image and then boots it inside the QEMU emulator.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Because a full build can take hours, you should check two variables in the
<code class="filename">build</code> directory that is created after you source the
<code class="filename">oe-init-build-env</code> script.
You can find these variables
<code class="filename">BB_NUMBER_THREADS</code> and <code class="filename">PARALLEL_MAKE</code>
in the <code class="filename">build/conf</code> directory in the
<code class="filename">local.conf</code> configuration file.
By default, these variables are commented out.
If your host development system supports multi-core and multi-thread capabilities,
you can uncomment these statements and set the variables to significantly shorten
the full build time.
As a guideline, set both <code class="filename">BB_NUMBER_THREADS</code> and
<code class="filename">PARALLEL_MAKE</code> to twice the number
of cores your machine supports.
</div><p>
The following two commands <code class="filename">source</code> the build environment setup script
and build the default <code class="filename">qemux86</code> image.
If necessary, the script creates the build directory:
</p><pre class="literallayout">
$ cd ~/poky
$ source oe-init-build-env
### Shell environment set up for builds. ###
You can now run 'bitbake &lt;target&gt;'
Common targets are:
core-image-minimal
core-image-sato
meta-toolchain
meta-toolchain-sdk
adt-installer
meta-ide-support
You can also run generated qemu images with a command like 'runqemu qemux86'
</pre><p>
</p><p>
The following <code class="filename">bitbake</code> command starts the build:
</p><pre class="literallayout">
$ bitbake -k core-image-minimal
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>Be sure to check the settings in the <code class="filename">local.conf</code>
before starting the build.</div><p>
</p><p>
After the build completes, you can start the QEMU emulator using the resulting image
<code class="filename">qemux86</code> as follows:
</p><pre class="literallayout">
$ runqemu qemux86
</pre><p>
</p><p>
As the image boots in the emulator, console message and status output appears
across the terminal window.
Because the output scrolls by quickly, it is difficult to read.
To examine the output, you log into the system using the
login <code class="filename">root</code> with no password.
Once you are logged in, issue the following command to scroll through the
console output:
</p><pre class="literallayout">
# dmesg | less
</pre><p>
</p><p>
Take note of the output as you will want to look for your inserted print command output
later in the example.
</p></div><div class="section" title="B.1.6. Changing the Source Code and Pushing it to the Bare Clone"><div class="titlepage"><div><div><h3 class="title"><a id="changing-the-source-code-and-pushing-it-to-the-bare-clone"></a>B.1.6. Changing the Source Code and Pushing it to the Bare Clone</h3></div></div></div><p>
The file you change in this example is named <code class="filename">calibrate.c</code>
and is located in the <code class="filename">my-linux-yocto-3.2-work</code> Git repository
(the copy of the bare clone) in <code class="filename">init</code>.
This example simply inserts several <code class="filename">printk</code> statements
at the beginning of the <code class="filename">calibrate_delay</code> function.
</p><p>
Here is the unaltered code at the start of this function:
</p><pre class="literallayout">
void __cpuinit calibrate_delay(void)
{
unsigned long lpj;
static bool printed;
int this_cpu = smp_processor_id();
if (per_cpu(cpu_loops_per_jiffy, this_cpu)) {
.
.
.
</pre><p>
</p><p>
Here is the altered code showing five new <code class="filename">printk</code> statements
near the top of the function:
</p><pre class="literallayout">
void __cpuinit calibrate_delay(void)
{
unsigned long lpj;
static bool printed;
int this_cpu = smp_processor_id();
printk("*************************************\n");
printk("* *\n");
printk("* HELLO YOCTO KERNEL *\n");
printk("* *\n");
printk("*************************************\n");
if (per_cpu(cpu_loops_per_jiffy, this_cpu)) {
.
.
.
</pre><p>
</p><p>
After making and saving your changes, you need to stage them for the push.
The following Git commands are one method of staging and committing your changes:
</p><pre class="literallayout">
$ git add calibrate.c
$ git commit --signoff
</pre><p>
</p><p>
Once the source code has been modified, you need to use Git to push the changes to
the bare clone.
If you do not push the changes, then the OpenEmbedded build system will not pick
up the changed source files.
</p><p>
The following command pushes the changes to the bare clone:
</p><pre class="literallayout">
$ git push origin common-pc-base:standard/default/common-pc/base
</pre><p>
</p></div><div class="section" title="B.1.7. Changing Build Parameters for Your Build"><div class="titlepage"><div><div><h3 class="title"><a id="changing-build-parameters-for-your-build"></a>B.1.7. Changing Build Parameters for Your Build</h3></div></div></div><p>
At this point, the source has been changed and pushed.
The example now defines some variables used by the OpenEmbedded build system
to locate your kernel source.
You essentially need to identify where to find the kernel recipe and the changed source code.
You also need to be sure some basic configurations are in place that identify the
type of machine you are building and to help speed up the build should your host support
multiple-core and thread capabilities.
</p><p>
Do the following to make sure the build parameters are set up for the example.
Once you set up these build parameters, they do not have to change unless you
change the target architecture of the machine you are building or you move
the bare clone, copy of the clone, or the <code class="filename">poky-extras</code> repository:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Build for the Correct Target Architecture:</em></span> The
<code class="filename">local.conf</code> file in the build directory defines the build's
target architecture.
By default, <code class="filename">MACHINE</code> is set to
<code class="filename">qemux86</code>, which specifies a 32-bit
<span class="trademark">Intel</span>® Architecture
target machine suitable for the QEMU emulator.
In this example, <code class="filename">MACHINE</code> is correctly configured.
</p></li><li class="listitem"><p><span class="emphasis"><em>Optimize Build Time:</em></span> Also in the
<code class="filename">local.conf</code> file are two variables that can speed your
build time if your host supports multi-core and multi-thread capabilities:
<code class="filename">BB_NUMBER_THREADS</code> and <code class="filename">PARALLEL_MAKE</code>.
If the host system has multiple cores then you can optimize build time
by setting both these variables to twice the number of
cores.</p></li><li class="listitem"><p><span class="emphasis"><em>Identify Your <code class="filename">meta-kernel-dev</code>
Layer:</em></span> The <code class="filename">BBLAYERS</code> variable in the
<code class="filename">bblayers.conf</code> file found in the
<code class="filename">poky/build/conf</code> directory needs to have the path to your local
<code class="filename">meta-kernel-dev</code> layer.
By default, the <code class="filename">BBLAYERS</code> variable contains paths to
<code class="filename">meta</code> and <code class="filename">meta-yocto</code> in the
<code class="filename">poky</code> Git repository.
Add the path to your <code class="filename">meta-kernel-dev</code> location.
Be sure to substitute your user information in the statement.
Here is an example:
</p><pre class="literallayout">
BBLAYERS = " \
/home/scottrif/poky/meta \
/home/scottrif/poky/meta-yocto \
/home/scottrif/poky/poky-extras/meta-kernel-dev \
"
</pre></li><li class="listitem"><p><span class="emphasis"><em>Identify Your Source Files:</em></span> In the
<code class="filename">linux-yocto_3.2.bbappend</code> file located in the
<code class="filename">poky-extras/meta-kernel-dev/recipes-kernel/linux</code>
directory, you need to identify the location of the
local source code, which in this example is the bare clone named
<code class="filename">linux-yocto-3.2.git</code>.
To do this, set the <code class="filename">KSRC_linux_yocto</code> variable to point to your
local <code class="filename">linux-yocto-3.2.git</code> Git repository by adding the
following statement.
Be sure to substitute your user information in the statement:
</p><pre class="literallayout">
KSRC_linux_yocto_3_2 ?= "/home/scottrif/linux-yocto-3.2.git"
</pre></li></ul></div><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>Before attempting to build the modified kernel, there is one more set of changes you
need to make in the <code class="filename">meta-kernel-dev</code> layer.
Because all the kernel <code class="filename">.bbappend</code> files are parsed during the
build process regardless of whether you are using them or not, you should either
comment out the <code class="filename">COMPATIBLE_MACHINE</code> statements in all
unused <code class="filename">.bbappend</code> files, or simply remove (or rename) all the files
except the one your are using for the build
(i.e. <code class="filename">linux-yocto_3.2.bbappend</code> in this example).</p><p>If you do not make one of these two adjustments, your machine will be compatible
with all the kernel recipes in the <code class="filename">meta-kernel-dev</code> layer.
When your machine is comapatible with all the kernel recipes, the build attempts
to build all kernels in the layer.
You could end up with build errors blocking your work.</p></div></div><div class="section" title="B.1.8. Building and Booting the Modified QEMU Kernel Image"><div class="titlepage"><div><div><h3 class="title"><a id="building-and-booting-the-modified-qemu-kernel-image"></a>B.1.8. Building and Booting the Modified QEMU Kernel Image</h3></div></div></div><p>
Next, you need to build the modified image.
Do the following:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Your environment should be set up since you previously sourced
the <code class="filename">oe-init-build-env</code> script.
If it isn't, source the script again from <code class="filename">poky</code>.
</p><pre class="literallayout">
$ cd ~/poky
$ source oe-init-build-env
</pre><p>
</p></li><li class="listitem"><p>Be sure old images are cleaned out by running the
<code class="filename">cleanall</code> BitBake task as follows from your build directory:
</p><pre class="literallayout">
$ bitbake -c cleanall linux-yocto
</pre><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>Never remove any files by hand from the <code class="filename">tmp/deploy</code>
directory insided the build directory.
Always use the BitBake <code class="filename">cleanall</code> task to clear
out previous builds.</div></li><li class="listitem"><p>Next, build the kernel image using this command:
</p><pre class="literallayout">
$ bitbake -k core-image-minimal
</pre></li><li class="listitem"><p>Finally, boot the modified image in the QEMU emulator
using this command:
</p><pre class="literallayout">
$ runqemu qemux86
</pre></li></ol></div><p>
</p><p>
Log into the machine using <code class="filename">root</code> with no password and then
use the following shell command to scroll through the console's boot output.
</p><pre class="literallayout">
# dmesg | less
</pre><p>
</p><p>
You should see the results of your <code class="filename">printk</code> statements
as part of the output.
</p></div></div><div class="section" title="B.2. Changing the Kernel Configuration"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="changing-the-kernel-configuration"></a>B.2. Changing the Kernel Configuration</h2></div></div></div><p>
This example changes the default behavior, which is "on", of the Symmetric
Multi-processing Support (<code class="filename">CONFIG_SMP</code>) to "off".
It is a simple example that demonstrates how to reconfigure the kernel.
</p><div class="section" title="B.2.1. Getting Set Up to Run this Example"><div class="titlepage"><div><div><h3 class="title"><a id="getting-set-up-to-run-this-example"></a>B.2.1. Getting Set Up to Run this Example</h3></div></div></div><p>
If you took the time to work through the example that modifies the kernel source code
in "<a class="link" href="#modifying-the-kernel-source-code" title="B.1. Modifying the Kernel Source Code">Modifying the Kernel Source
Code</a>" you should already have the source directory set up on your
host machine.
If this is the case, go to the next section, which is titled
"<a class="link" href="#examining-the-default-config-smp-behavior" title="B.2.2. Examining the Default  CONFIG_SMP Behavior">Examining the Default
<code class="filename">CONFIG_SMP</code> Behavior</a>", and continue with the
example.
</p><p>
If you don't have the source directory established on your system,
you can get them through tarball extraction or by
cloning the <code class="filename">poky</code> Git repository.
This example uses <code class="filename">poky</code> as the root directory of the
<a class="link" href="#source-directory">source directory</a>.
See the bulleted item
"<a class="link" href="#local-yp-release">Yocto Project Release</a>"
for information on how to get these files.
</p><p>
Once you have the local copy of the repository set up,
you have many development branches from which you can work.
From inside the repository you can see the branch names and the tag names used
in the upstream Git repository using either of the following commands:
</p><pre class="literallayout">
$ cd poky
$ git branch -a
$ git tag -l
</pre><p>
This example uses the Yocto Project 1.3 Release code named "1.2+snapshot",
which maps to the <code class="filename">1.2+snapshot</code> branch in the repository.
The following commands create and checkout the local <code class="filename">1.2+snapshot</code>
branch:
</p><pre class="literallayout">
$ git checkout -b 1.2+snapshot origin/1.2+snapshot
Branch 1.2+snapshot set up to track remote branch 1.2+snapshot from origin.
Switched to a new branch '1.2+snapshot'
</pre><p>
</p><p>
Next, you need to build the default <code class="filename">qemux86</code> image that you
can boot using QEMU.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Because a full build can take hours, you should check two variables in the
<code class="filename">build</code> directory that is created after you source the
<code class="filename">oe-init-build-env</code> script.
You can find these variables
<code class="filename">BB_NUMBER_THREADS</code> and <code class="filename">PARALLEL_MAKE</code>
in the <code class="filename">build/conf</code> directory in the
<code class="filename">local.conf</code> configuration file.
By default, these variables are commented out.
If your host development system supports multi-core and multi-thread capabilities,
you can uncomment these statements and set the variables to significantly shorten
the full build time.
As a guideline, set both the <code class="filename">BB_NUMBER_THREADS</code> and the
<code class="filename">PARALLEL_MAKE</code> variables to twice the number
of cores your machine supports.
</div><p>
The following two commands <code class="filename">source</code> the build environment setup script
and build the default <code class="filename">qemux86</code> image.
If necessary, the script creates the build directory:
</p><pre class="literallayout">
$ cd ~/poky
$ source oe-init-build-env
### Shell environment set up for builds. ###
You can now run 'bitbake &lt;target&gt;'
Common targets are:
core-image-minimal
core-image-sato
meta-toolchain
meta-toolchain-sdk
adt-installer
meta-ide-support
You can also run generated qemu images with a command like 'runqemu qemux86'
</pre><p>
</p><p>
The following <code class="filename">bitbake</code> command starts the build:
</p><pre class="literallayout">
$ bitbake -k core-image-minimal
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>Be sure to check the settings in the <code class="filename">local.conf</code>
before starting the build.</div><p>
</p></div><div class="section" title="B.2.2. Examining the Default  CONFIG_SMP Behavior"><div class="titlepage"><div><div><h3 class="title"><a id="examining-the-default-config-smp-behavior"></a>B.2.2. Examining the Default  <code class="filename">CONFIG_SMP</code> Behavior</h3></div></div></div><p>
By default, <code class="filename">CONFIG_SMP</code> supports multiple processor machines.
To see this default setting from within the QEMU emulator, boot your image using
the emulator as follows:
</p><pre class="literallayout">
$ runqemu qemux86 qemuparams="-smp 4"
</pre><p>
</p><p>
Login to the machine using <code class="filename">root</code> with no password.
After logging in, enter the following command to see how many processors are
being supported in the emulator.
The emulator reports support for the number of processors you specified using
the <code class="filename">-smp</code> option, four in this case:
</p><pre class="literallayout">
# cat /proc/cpuinfo | grep processor
processor : 0
processor : 1
processor : 2
processor : 3
#
</pre><p>
To check the setting for <code class="filename">CONFIG_SMP</code>, you can use the
following command:
</p><pre class="literallayout">
zcat /proc/config.gz | grep CONFIG_SMP
</pre><p>
The console returns the following showing that multi-processor machine support
is set:
</p><pre class="literallayout">
CONFIG_SMP=y
</pre><p>
Logout of the emulator using the <code class="filename">exit</code> command and
then close it down.
</p></div><div class="section" title="B.2.3. Changing the  CONFIG_SMP Configuration Using  menuconfig"><div class="titlepage"><div><div><h3 class="title"><a id="changing-the-config-smp-configuration-using-menuconfig"></a>B.2.3. Changing the  <code class="filename">CONFIG_SMP</code> Configuration Using  <code class="filename">menuconfig</code></h3></div></div></div><p>
The <code class="filename">menuconfig</code> tool provides an interactive method with which
to set kernel configurations.
You need to run <code class="filename">menuconfig</code> inside the Yocto BitBake environment.
Thus, the environment must be set up using the <code class="filename">oe-init-build-env</code>
script found in the build directory.
If you have not sourced this script do so with the following commands:
</p><pre class="literallayout">
$ cd ~/poky
$ source oe-init-build-env
</pre><p>
</p><p>
After setting up the environment to run <code class="filename">menuconfig</code>, you are ready
to use the tool to interactively change the kernel configuration.
In this example, we are basing our changes on the <code class="filename">linux-yocto-3.2</code>
kernel.
The OpenEmbedded build system recognizes this kernel as
<code class="filename">linux-yocto</code>.
Thus, the following commands from the shell in which you previously sourced the
environment initialization script cleans the shared state cache and the
<a class="link" href="#var-WORKDIR" target="_top"><code class="filename">WORKDIR</code></a>
directory and then builds and launches <code class="filename">menuconfig</code>:
</p><pre class="literallayout">
$ bitbake linux-yocto -c menuconfig
</pre><p>
</p><p>
Once <code class="filename">menuconfig</code> launches, navigate through the user interface
to find the <code class="filename">CONFIG_SMP</code> configuration setting.
You can find it at <code class="filename">Processor Type and Features</code>.
The configuration selection is
<code class="filename">Symmetric Multi-processing Support</code>.
After using the arrow keys to highlight this selection, press "n" to turn it off.
Then, exit out and save your selections.
</p><p>
Once you save the selection, the <code class="filename">.config</code> configuration file
is updated.
This is the file that the build system uses to configure the Yocto Project kernel
when it is built.
You can find and examine this file in the build directory.
This example uses the following:
</p><pre class="literallayout">
~/poky/build/tmp/work/qemux86-poky-linux/linux-yocto-3.2.11+git1+84f...
...656ed30-r1/linux-qemux86-standard-build
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
The previous example directory is artificially split and many of the characters
in the actual filename are omitted in order to make it more readable.
Also, depending on the kernel you are using, the exact pathname might differ
slightly.
</div><p>
</p><p>
Within the <code class="filename">.config</code> file, you can see the following setting:
</p><pre class="literallayout">
# CONFIG_SMP is not set
</pre><p>
</p><p>
A good method to isolate changed configurations is to use a combination of the
<code class="filename">menuconfig</code> tool and simple shell commands.
Before changing configurations with <code class="filename">menuconfig</code>, copy the
existing <code class="filename">.config</code> and rename it to something else,
use <code class="filename">menuconfig</code> to make
as many changes an you want and save them, then compare the renamed configuration
file against the newly created file.
You can use the resulting differences as your base to create configuration fragments
to permanently save in your kernel layer.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Be sure to make a copy of the <code class="filename">.config</code> and don't just
rename it.
The build system needs an existing <code class="filename">.config</code>
from which to work.
</div><p>
</p></div><div class="section" title="B.2.4. Recompiling the Kernel and Testing the New Configuration"><div class="titlepage"><div><div><h3 class="title"><a id="recompiling-the-kernel-and-testing-the-new-configuration"></a>B.2.4. Recompiling the Kernel and Testing the New Configuration</h3></div></div></div><p>
At this point, you are ready to recompile your kernel image with
the new setting in effect using the BitBake command below:
</p><pre class="literallayout">
$ bitbake linux-yocto
</pre><p>
</p><p>
Now run the QEMU emulator and pass it the same multi-processor option as before:
</p><pre class="literallayout">
$ runqemu qemux86 qemuparams="-smp 4"
</pre><p>
</p><p>
Login to the machine using <code class="filename">root</code> with no password
and test for the number of processors the kernel supports:
</p><pre class="literallayout">
# cat /proc/cpuinfo | grep processor
processor : 0
#
</pre><p>
</p><p>
From the output, you can see that the kernel no longer supports multi-processor systems.
The output indicates support for a single processor. You can verify the
<code class="filename">CONFIG_SMP</code> setting by using this command:
</p><pre class="literallayout">
zcat /proc/config.gz | grep CONFIG_SMP
</pre><p>
The console returns the following output:
</p><pre class="literallayout">
# CONFIG_SMP is not set
</pre><p>
You have successfully reconfigured the kernel.
</p></div></div><div class="section" title="B.3. Adding Kernel Recipes"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="adding-kernel-recipes"></a>B.3. Adding Kernel Recipes</h2></div></div></div><p>
A future release of this manual will present an example that adds kernel recipes, which provide
new functionality to the kernel.
</p><p>
</p><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="180"><tr style="height: 270px"><td align="center"><img src="figures/wip.png" align="middle" width="180" /></td></tr></table><p>
</p></div></div>
</div>
<table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="100%"><tr><td align="left"><img src="figures/adt-title.png" align="left" width="100%" /></td></tr></table>
<div xml:lang="en" class="book" lang="en"><div class="titlepage"><div><div><h1 class="title"><a id="adt-manual"></a></h1></div><div><div class="authorgroup">
<div class="author"><h3 class="author"><span class="firstname">Jessica</span> <span class="surname">Zhang</span></h3><div class="affiliation">
<span class="orgname">Intel Corporation<br /></span>
</div><code class="email">&lt;<a class="email" href="mailto:jessica.zhang@intel.com">jessica.zhang@intel.com</a>&gt;</code></div>
</div></div><div><p class="copyright">Copyright © 2010-2012 Linux Foundation</p></div><div><div class="legalnotice" title="Legal Notice"><a id="id1499739"></a>
<p>
Permission is granted to copy, distribute and/or modify this document under
the terms of the <a class="ulink" href="http://creativecommons.org/licenses/by-sa/2.0/uk/" target="_top">Creative Commons Attribution-Share Alike 2.0 UK: England &amp; Wales</a> as published by Creative Commons.
</p>
<div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Due to production processes, there could be differences between the Yocto Project
documentation bundled in the release tarball and the
Yocto Project Application Developer's Guide on
the <a class="ulink" href="http://www.yoctoproject.org" target="_top">Yocto Project</a> website.
For the latest version of this manual, see the manual on the website.
</div>
</div></div><div><div class="revhistory"><table border="1" width="100%" summary="Revision history"><tr><th align="left" valign="top" colspan="2"><b>Revision History</b></th></tr>
<tr><td align="left">Revision 1.0</td><td align="left">6 April 2011</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.0 Release.</td></tr>
<tr><td align="left">Revision 1.0.1</td><td align="left">23 May 2011</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.0.1 Release.</td></tr>
<tr><td align="left">Revision 1.1</td><td align="left">6 October 2011</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.1 Release.</td></tr>
<tr><td align="left">Revision 1.2</td><td align="left">April 2012</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.2 Release.</td></tr>
<tr><td align="left">Revision 1.3</td><td align="left">Sometime in 2012</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.3 Release.</td></tr>
</table></div></div></div><hr /></div>
<div class="chapter" title="Chapter 1. Introduction"><div class="titlepage"><div><div><h2 class="title"><a id="adt-intro"></a>Chapter 1. Introduction</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#adt-intro-section">1.1. The Application Development Toolkit (ADT)</a></span></dt><dd><dl><dt><span class="section"><a href="#the-cross-toolchain">1.1.1. The Cross-Toolchain</a></span></dt><dt><span class="section"><a href="#sysroot">1.1.2. Sysroot</a></span></dt><dt><span class="section"><a href="#eclipse-overview">1.1.3. Eclipse Yocto Plug-in</a></span></dt><dt><span class="section"><a href="#the-qemu-emulator">1.1.4. The QEMU Emulator</a></span></dt><dt><span class="section"><a href="#user-space-tools">1.1.5. User-Space Tools</a></span></dt></dl></dd></dl></div><p>
Welcome to the Yocto Project Application Developer's Guide.
This manual provides information that lets you begin developing applications
using the Yocto Project.
</p><p>
The Yocto Project provides an application development environment based on
an Application Development Toolkit (ADT) and the availability of stand-alone
cross-development toolchains and other tools.
This manual describes the ADT and how you can configure and install it,
how to access and use the cross-development toolchains, how to
customize the development packages installation,
how to use command line development for both Autotools-based and Makefile-based projects,
and an introduction to the Eclipse Yocto Plug-in.
</p><div class="section" title="1.1. The Application Development Toolkit (ADT)"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="adt-intro-section"></a>1.1. The Application Development Toolkit (ADT)</h2></div></div></div><p>
Part of the Yocto Project development solution is an Application Development
Toolkit (ADT).
The ADT provides you with a custom-built, cross-development
platform suited for developing a user-targeted product application.
</p><p>
Fundamentally, the ADT consists of the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>An architecture-specific cross-toolchain and matching
sysroot both built by the OpenEmbedded build system, which uses Poky.
The toolchain and sysroot are based on a metadata configuration and extensions,
which allows you to cross-develop on the host machine for the target hardware.
</p></li><li class="listitem"><p>The Eclipse IDE Yocto Plug-in.</p></li><li class="listitem"><p>The Quick EMUlator (QEMU), which lets you simulate target hardware.
</p></li><li class="listitem"><p>Various user-space tools that greatly enhance your application
development experience.</p></li></ul></div><p>
</p><div class="section" title="1.1.1. The Cross-Toolchain"><div class="titlepage"><div><div><h3 class="title"><a id="the-cross-toolchain"></a>1.1.1. The Cross-Toolchain</h3></div></div></div><p>
The cross-toolchain consists of a cross-compiler, cross-linker, and cross-debugger
that are used to develop user-space applications for targeted hardware.
This toolchain is created either by running the ADT Installer script or
through a build directory that is based on your metadata
configuration or extension for your targeted device.
The cross-toolchain works with a matching target sysroot.
</p></div><div class="section" title="1.1.2. Sysroot"><div class="titlepage"><div><div><h3 class="title"><a id="sysroot"></a>1.1.2. Sysroot</h3></div></div></div><p>
The matching target sysroot contains needed headers and libraries for generating
binaries that run on the target architecture.
The sysroot is based on the target root filesystem image that is built by
the OpenEmbedded build system Poky and uses the same metadata configuration
used to build the cross-toolchain.
</p></div><div class="section" title="1.1.3. Eclipse Yocto Plug-in"><div class="titlepage"><div><div><h3 class="title"><a id="eclipse-overview"></a>1.1.3. Eclipse Yocto Plug-in</h3></div></div></div><p>
The Eclipse IDE is a popular development environment and it fully supports
development using the Yocto Project.
When you install and configure the Eclipse Yocto Project Plug-in into
the Eclipse IDE, you maximize your Yocto Project experience.
Installing and configuring the Plug-in results in an environment that
has extensions specifically designed to let you more easily develop software.
These extensions allow for cross-compilation, deployment, and execution of
your output into a QEMU emulation session.
You can also perform cross-debugging and profiling.
The environment also supports a suite of tools that allows you to perform
remote profiling, tracing, collection of power data, collection of
latency data, and collection of performance data.
</p><p>
For information about the application development workflow that uses the Eclipse
IDE and for a detailed example of how to install and configure the Eclipse
Yocto Project Plug-in, see the
"<a class="link" href="#adt-eclipse" target="_top">Working Within Eclipse</a>" section
of the Yocto Project Development Manual.
</p></div><div class="section" title="1.1.4. The QEMU Emulator"><div class="titlepage"><div><div><h3 class="title"><a id="the-qemu-emulator"></a>1.1.4. The QEMU Emulator</h3></div></div></div><p>
The QEMU emulator allows you to simulate your hardware while running your
application or image.
QEMU is made available a number of ways:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>If you use the ADT Installer script to install ADT, you can
specify whether or not to install QEMU.</p></li><li class="listitem"><p>If you have downloaded a Yocto Project release and unpacked
it to create a source directory and you have sourced
the environment setup script, QEMU is installed and automatically
available.</p></li><li class="listitem"><p>If you have installed the cross-toolchain
tarball and you have sourcing the toolchain's setup environment script, QEMU
is also installed and automatically available.</p></li></ul></div><p>
</p></div><div class="section" title="1.1.5. User-Space Tools"><div class="titlepage"><div><div><h3 class="title"><a id="user-space-tools"></a>1.1.5. User-Space Tools</h3></div></div></div><p>
User-space tools are included as part of the distribution.
You will find these tools helpful during development.
The tools include LatencyTOP, PowerTOP, OProfile, Perf, SystemTap, and Lttng-ust.
These tools are common development tools for the Linux platform.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>LatencyTOP:</em></span> LatencyTOP focuses on latency
that causes skips in audio,
stutters in your desktop experience, or situations that overload your server
even when you have plenty of CPU power left.
You can find out more about LatencyTOP at
<a class="ulink" href="http://www.latencytop.org/" target="_top">http://www.latencytop.org/</a>.</p></li><li class="listitem"><p><span class="emphasis"><em>PowerTOP:</em></span> Helps you determine what
software is using the most power.
You can find out more about PowerTOP at
<a class="ulink" href="http://www.linuxpowertop.org/" target="_top">http://www.linuxpowertop.org/</a>.</p></li><li class="listitem"><p><span class="emphasis"><em>OProfile:</em></span> A system-wide profiler for Linux
systems that is capable of profiling all running code at low overhead.
You can find out more about OProfile at
<a class="ulink" href="http://oprofile.sourceforge.net/about/" target="_top">http://oprofile.sourceforge.net/about/</a>.</p></li><li class="listitem"><p><span class="emphasis"><em>Perf:</em></span> Performance counters for Linux used
to keep track of certain types of hardware and software events.
For more information on these types of counters see
<a class="ulink" href="https://perf.wiki.kernel.org/" target="_top">https://perf.wiki.kernel.org/</a> and click
on “Perf tools.”</p></li><li class="listitem"><p><span class="emphasis"><em>SystemTap:</em></span> A free software infrastructure
that simplifies information gathering about a running Linux system.
This information helps you diagnose performance or functional problems.
SystemTap is not available as a user-space tool through the Eclipse IDE Yocto Plug-in.
See <a class="ulink" href="http://sourceware.org/systemtap" target="_top">http://sourceware.org/systemtap</a> for more information
on SystemTap.</p></li><li class="listitem"><p><span class="emphasis"><em>Lttng-ust:</em></span> A User-space Tracer designed to
provide detailed information on user-space activity.
See <a class="ulink" href="http://lttng.org/ust" target="_top">http://lttng.org/ust</a> for more information on Lttng-ust.
</p></li></ul></div><p>
</p></div></div></div>
<div class="chapter" title="Chapter 2. Preparing for Application Development"><div class="titlepage"><div><div><h2 class="title"><a id="adt-prepare"></a>Chapter 2. Preparing for Application Development</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#installing-the-adt">2.1. Installing the ADT and Toolchains</a></span></dt><dd><dl><dt><span class="section"><a href="#using-the-adt-installer">2.1.1. Using the ADT Installer</a></span></dt><dt><span class="section"><a href="#using-an-existing-toolchain-tarball">2.1.2. Using a Cross-Toolchain Tarball</a></span></dt><dt><span class="section"><a href="#using-the-toolchain-from-within-the-build-tree">2.1.3. Using BitBake and the Build Directory</a></span></dt></dl></dd><dt><span class="section"><a href="#setting-up-the-cross-development-environment">2.2. Setting Up the Cross-Development Environment</a></span></dt><dt><span class="section"><a href="#securing-kernel-and-filesystem-images">2.3. Securing Kernel and Filesystem Images</a></span></dt><dd><dl><dt><span class="section"><a href="#getting-the-images">2.3.1. Getting the Images</a></span></dt><dt><span class="section"><a href="#extracting-the-root-filesystem">2.3.2. Extracting the Root Filesystem</a></span></dt></dl></dd></dl></div><p>
In order to develop applications, you need set up your host development system.
Several ways exist that allow you to install cross-development tools, QEMU, the
Eclipse Yocto Plug-in, and other tools.
This chapter describes how to prepare for application development.
</p><div class="section" title="2.1. Installing the ADT and Toolchains"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="installing-the-adt"></a>2.1. Installing the ADT and Toolchains</h2></div></div></div><p>
The following list describes installation methods that set up varying degrees of tool
availabiltiy on your system.
Regardless of the installation method you choose,
you must <code class="filename">source</code> the cross-toolchain
environment setup script before you use a toolchain.
See the "<a class="link" href="#setting-up-the-cross-development-environment" title="2.2. Setting Up the Cross-Development Environment">Setting Up the
Cross-Development Environment</a>" section for more information.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>Avoid mixing installation methods when installing toolchains for different architectures.
For example, avoid using the ADT Installer to install some toolchains and then hand-installing
cross-development toolchains from downloaded tarballs to install toolchains
for different architectures.
Mixing installation methods can result in situations where the ADT Installer becomes
unreliable and might not install the toolchain.</p><p>If you must mix installation methods, you might avoid problems by deleting
<code class="filename">/var/lib/opkg</code>, thus purging the <code class="filename">opkg</code> package
metadata</p></div><p>
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Use the ADT Installer Script:</em></span>
This method is the recommended way to install the ADT because it
automates much of the process for you.
For example, you can configure the installation to install the QEMU emulator
and the user-space NFS, specify which root filesystem profiles to download,
and define the target sysroot location.</p></li><li class="listitem"><p><span class="emphasis"><em>Use an Existing Toolchain Tarball:</em></span>
Using this method, you select and download an architecture-specific
toolchain tarball and then hand-install the toolchain.
If you use this method, you just get the cross-toolchain and QEMU - you do not
get any of the other mentioned benefits had you run the ADT Installer script.</p></li><li class="listitem"><p><span class="emphasis"><em>Use the Toolchain from within the Build Directory:</em></span>
If you already have a
<a class="link" href="#build-directory" target="_top">build directory</a>,
you can build the cross-toolchain within the directory.
However, like the previous method mentioned, you only get the cross-toolchain and QEMU - you
do not get any of the other benefits without taking separate steps.</p></li></ul></div><p>
</p><div class="section" title="2.1.1. Using the ADT Installer"><div class="titlepage"><div><div><h3 class="title"><a id="using-the-adt-installer"></a>2.1.1. Using the ADT Installer</h3></div></div></div><p>
To run the ADT Installer, you need to first get the ADT Installer tarball and then run the ADT
Installer Script.
</p><div class="section" title="2.1.1.1. Getting the ADT Installer Tarball"><div class="titlepage"><div><div><h4 class="title"><a id="getting-the-adt-installer-tarball"></a>2.1.1.1. Getting the ADT Installer Tarball</h4></div></div></div><p>
The ADT Installer is contained in the ADT Installer tarball.
You can download the tarball into any directory from the
<a class="ulink" href="http://downloads.yoctoproject.org/releases" target="_top">Index of Releases</a>, specifically
at
<a class="ulink" href="http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/adt_installer" target="_top">http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/adt_installer</a>.
Or, you can use BitBake to generate the tarball inside the existing
<a class="link" href="#build-directory" target="_top">build directory</a>.
</p><p>
If you use BitBake to generate the ADT Installer tarball, you must
<code class="filename">source</code> the environment setup script
(<code class="filename">oe-init-build-env</code>) located
in the source directory before running the <code class="filename">bitbake</code>
command that creates the tarball.
</p><p>
The following example commands download the Poky tarball, set up the
<a class="link" href="#source-directory" target="_top">source directory</a>,
set up the environment while also creating the default build directory,
and run the <code class="filename">bitbake</code> command that results in the tarball
<code class="filename">~/yocto-project/build/tmp/deploy/sdk/adt_installer.tar.bz2</code>:
</p><pre class="literallayout">
$ cd ~
$ mkdir yocto-project
$ cd yocto-project
$ wget http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/poky-1.2+snapshot-8.0.tar.bz2
$ tar xjf poky-1.2+snapshot-8.0.tar.bz2
$ source poky-1.2+snapshot-8.0/oe-init-build-env
$ bitbake adt-installer
</pre><p>
</p></div><div class="section" title="2.1.1.2. Configuring and Running the ADT Installer Script"><div class="titlepage"><div><div><h4 class="title"><a id="configuring-and-running-the-adt-installer-script"></a>2.1.1.2. Configuring and Running the ADT Installer Script</h4></div></div></div><p>
Before running the ADT Installer script, you need to unpack the tarball.
You can unpack the tarball in any directory you wish.
For example, this command copies the ADT Installer tarball from where
it was built into the home directory and then unpacks the tarball into
a top-level directory named <code class="filename">adt-installer</code>:
</p><pre class="literallayout">
$ cd ~
$ cp ~/poky/build/tmp/deploy/sdk/adt_installer.tar.bz2 $HOME
$ tar -xjf adt_installer.tar.bz2
</pre><p>
Unpacking it creates the directory <code class="filename">adt-installer</code>,
which contains the ADT Installer script (<code class="filename">adt_installer</code>)
and its configuration file (<code class="filename">adt_installer.conf</code>).
</p><p>
Before you run the script, however, you should examine the ADT Installer configuration
file and be sure you are going to get what you want.
Your configurations determine which kernel and filesystem image are downloaded.
</p><p>
The following list describes the configurations you can define for the ADT Installer.
For configuration values and restrictions, see the comments in
the <code class="filename">adt-installer.conf</code> file:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename">YOCTOADT_REPO</code>: This area
includes the IPKG-based packages and the root filesystem upon which
the installation is based.
If you want to set up your own IPKG repository pointed to by
<code class="filename">YOCTOADT_REPO</code>, you need to be sure that the
directory structure follows the same layout as the reference directory
set up at <a class="ulink" href="http://adtrepo.yoctoproject.org" target="_top">http://adtrepo.yoctoproject.org</a>.
Also, your repository needs to be accessible through HTTP.</p></li><li class="listitem"><p><code class="filename">YOCTOADT_TARGETS</code>: The machine
target architectures for which you want to set up cross-development
environments.</p></li><li class="listitem"><p><code class="filename">YOCTOADT_QEMU</code>: Indicates whether
or not to install the emulator QEMU.</p></li><li class="listitem"><p><code class="filename">YOCTOADT_NFS_UTIL</code>: Indicates whether
or not to install user-mode NFS.
If you plan to use the Eclipse IDE Yocto plug-in against QEMU,
you should install NFS.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>To boot QEMU images using our userspace NFS server, you need
to be running <code class="filename">portmap</code> or <code class="filename">rpcbind</code>.
If you are running <code class="filename">rpcbind</code>, you will also need to add the
<code class="filename">-i</code> option when <code class="filename">rpcbind</code> starts up.
Please make sure you understand the security implications of doing this.
You might also have to modify your firewall settings to allow
NFS booting to work.</div></li><li class="listitem"><p><code class="filename">YOCTOADT_ROOTFS_&lt;arch&gt;</code>: The root
filesystem images you want to download from the
<code class="filename">YOCTOADT_IPKG_REPO</code> repository.</p></li><li class="listitem"><p><code class="filename">YOCTOADT_TARGET_SYSROOT_IMAGE_&lt;arch&gt;</code>: The
particular root filesystem used to extract and create the target sysroot.
The value of this variable must have been specified with
<code class="filename">YOCTOADT_ROOTFS_&lt;arch&gt;</code>.
For example, if you downloaded both <code class="filename">minimal</code> and
<code class="filename">sato-sdk</code> images by setting
<code class="filename">YOCTOADT_ROOTFS_&lt;arch&gt;</code>
to "minimal sato-sdk", then <code class="filename">YOCTOADT_ROOTFS_&lt;arch&gt;</code>
must be set to either <code class="filename">minimal</code> or
<code class="filename">sato-sdk</code>.</p></li><li class="listitem"><p><code class="filename">YOCTOADT_TARGET_SYSROOT_LOC_&lt;arch&gt;</code>: The
location on the development host where the target sysroot is created.
</p></li></ul></div><p>
</p><p>
After you have configured the <code class="filename">adt_installer.conf</code> file,
run the installer using the following command.
Be sure that you are not trying to use cross-compilation tools.
When you run the installer, the environment must use a
host <code class="filename">gcc</code>:
</p><pre class="literallayout">
$ ./adt_installer
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
The ADT Installer requires the <code class="filename">libtool</code> package to complete.
If you install the recommended packages as described in
"<a class="link" href="#packages" target="_top">The Packages</a>"
section of the Yocto Project Quick Start, then you will have libtool installed.
</div><p>
Once the installer begins to run, you are asked whether you want to run in
interactive or silent mode.
If you want to closely monitor the installation, choose “I” for interactive
mode rather than “S” for silent mode.
Follow the prompts from the script to complete the installation.
</p><p>
Once the installation completes, the ADT, which includes the cross-toolchain, is installed.
You will notice environment setup files for the cross-toolchain in
<code class="filename">/opt/poky/1.3</code>,
and image tarballs in the <code class="filename">adt-installer</code>
directory according to your installer configurations, and the target sysroot located
according to the <code class="filename">YOCTOADT_TARGET_SYSROOT_LOC_&lt;arch&gt;</code> variable
also in your configuration file.
</p></div></div><div class="section" title="2.1.2. Using a Cross-Toolchain Tarball"><div class="titlepage"><div><div><h3 class="title"><a id="using-an-existing-toolchain-tarball"></a>2.1.2. Using a Cross-Toolchain Tarball</h3></div></div></div><p>
If you want to simply install the cross-toolchain by hand, you can do so by using an existing
cross-toolchain tarball.
If you use this method to install the cross-toolchain and you still need to install the target
sysroot, you will have to install sysroot separately.
</p><p>
Follow these steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Go to
<a class="ulink" href="http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/toolchain/" target="_top">http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/toolchain/</a>
and find the folder that matches your host development system
(i.e. <code class="filename">i686</code> for 32-bit machines or
<code class="filename">x86-64</code> for 64-bit machines).</p></li><li class="listitem"><p>Go into that folder and download the toolchain tarball whose name
includes the appropriate target architecture.
For example, if your host development system is an Intel-based 64-bit system and
you are going to use your cross-toolchain for an Intel-based 32-bit target, go into the
<code class="filename">x86_64</code> folder and download the following tarball:
</p><pre class="literallayout">
poky-eglibc-x86_64-i586-toolchain-gmae-1.3.tar.bz2
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>As an alternative to steps one and two, you can build the toolchain tarball
if you have a <a class="link" href="#build-directory" target="_top">build directory</a>.
If you need GMAE, you should use the <code class="filename">bitbake meta-toolchain-gmae</code>
command.
The resulting tarball will support such development.
However, if you are not concerned with GMAE,
you can generate the tarball using <code class="filename">bitbake meta-toolchain</code>.</p><p>Use the appropriate <code class="filename">bitbake</code> command only after you have
sourced the <code class="filename">oe-build-init-env</code> script located in the source
directory.
When the <code class="filename">bitbake</code> command completes, the tarball will
be in <code class="filename">tmp/deploy/sdk</code> in the build directory.
</p></div></li><li class="listitem"><p>Make sure you are in the root directory with root privileges and then expand
the tarball.
The tarball expands into <code class="filename">/opt/poky/1.3</code>.
Once the tarball is expanded, the cross-toolchain is installed.
You will notice environment setup files for the cross-toolchain in the directory.
</p></li></ol></div><p>
</p></div><div class="section" title="2.1.3. Using BitBake and the Build Directory"><div class="titlepage"><div><div><h3 class="title"><a id="using-the-toolchain-from-within-the-build-tree"></a>2.1.3. Using BitBake and the Build Directory</h3></div></div></div><p>
A final way of making the cross-toolchain available is to use BitBake
to generate the toolchain within an existing
<a class="link" href="#build-directory" target="_top">build directory</a>.
This method does not install the toolchain into the
<code class="filename">/opt</code> directory.
As with the previous method, if you need to install the target sysroot, you must
do that separately as well.
</p><p>
Follow these steps to generate the toolchain into the build directory:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Source the environment setup script
<code class="filename">oe-init-build-env</code> located in the
<a class="link" href="#source-directory" target="_top">source directory</a>.
</p></li><li class="listitem"><p>At this point, you should be sure that the
<a class="link" href="#var-MACHINE" target="_top"><code class="filename">MACHINE</code></a> variable
in the <code class="filename">local.conf</code> file found in the
<code class="filename">conf</code> directory of the build directory
is set for the target architecture.
Comments within the <code class="filename">local.conf</code> file list the values you
can use for the <code class="filename">MACHINE</code> variable.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>You can populate the build directory with the cross-toolchains for more
than a single architecture.
You just need to edit the <code class="filename">MACHINE</code> variable in the
<code class="filename">local.conf</code> file and re-run the BitBake
command.</div></li><li class="listitem"><p>Run <code class="filename">bitbake meta-ide-support</code> to complete the
cross-toolchain generation.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>If you change out of your working directory after you
<code class="filename">source</code> the environment setup script and before you run
the <code class="filename">bitbake</code> command, the command might not work.
Be sure to run the <code class="filename">bitbake</code> command immediately
after checking or editing the <code class="filename">local.conf</code> but without
changing out of your working directory.</div><p>
Once the <code class="filename">bitbake</code> command finishes,
the cross-toolchain is generated and populated within the build directory.
You will notice environment setup files for the cross-toolchain in the
build directory in the <code class="filename">tmp</code> directory.
Setup script filenames contain the strings <code class="filename">environment-setup</code>.
</p></li></ol></div><p>
</p></div></div><div class="section" title="2.2. Setting Up the Cross-Development Environment"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="setting-up-the-cross-development-environment"></a>2.2. Setting Up the Cross-Development Environment</h2></div></div></div><p>
Before you can develop using the cross-toolchain, you need to set up the
cross-development environment by sourcing the toolchain's environment setup script.
If you used the ADT Installer or hand-installed cross-toolchain,
then you can find this script in the <code class="filename">/opt/poky/1.3</code>
directory.
If you installed the toolchain in the
<a class="link" href="#build-directory" target="_top">build directory</a>,
you can find the environment setup
script for the toolchain in the build directory's <code class="filename">tmp</code> directory.
</p><p>
Be sure to run the environment setup script that matches the architecture for
which you are developing.
Environment setup scripts begin with the string “<code class="filename">environment-setup</code>”
and include as part of their name the architecture.
For example, the toolchain environment setup script for a 64-bit IA-based architecture would
be the following:
</p><pre class="literallayout">
/opt/poky/1.3/environment-setup-x86_64-poky-linux
</pre><p>
</p></div><div class="section" title="2.3. Securing Kernel and Filesystem Images"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="securing-kernel-and-filesystem-images"></a>2.3. Securing Kernel and Filesystem Images</h2></div></div></div><p>
You will need to have a kernel and filesystem image to boot using your
hardware or the QEMU emulator.
Furthermore, if you plan on booting your image using NFS or you want to use the root filesystem
as the target sysroot, you need to extract the root filesystem.
</p><div class="section" title="2.3.1. Getting the Images"><div class="titlepage"><div><div><h3 class="title"><a id="getting-the-images"></a>2.3.1. Getting the Images</h3></div></div></div><p>
To get the kernel and filesystem images, you either have to build them or download
pre-built versions.
You can find examples for both these situations in the
"<a class="link" href="#test-run" target="_top">A Quick Test Run</a>" section of
the Yocto Project Quick Start.
</p><p>
The Yocto Project ships basic kernel and filesystem images for several
architectures (<code class="filename">x86</code>, <code class="filename">x86-64</code>,
<code class="filename">mips</code>, <code class="filename">powerpc</code>, and <code class="filename">arm</code>)
that you can use unaltered in the QEMU emulator.
These kernel images reside in the release
area - <a class="ulink" href="http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/machines" target="_top">http://downloads.yoctoproject.org/releases/yocto/yocto-1.3/machines</a>
and are ideal for experimentation using Yocto Project.
For information on the image types you can build using the OpenEmbedded build system,
see the
"<a class="link" href="#ref-images" target="_top">Images</a>" chapter in
the Yocto Project Reference Manual.
</p><p>
If you plan on remotely deploying and debugging your application from within the
Eclipse IDE, you must have an image that contains the Yocto Target Communication
Framework (TCF) agent (<code class="filename">tcf-agent</code>).
By default, the Yocto Project provides only one type pre-built image that contains the
<code class="filename">tcf-agent</code>.
And, those images are SDK (e.g.<code class="filename">core-image-sato-sdk</code>).
</p><p>
If you want to use a different image type that contains the <code class="filename">tcf-agent</code>,
you can do so one of two ways:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Modify the <code class="filename">conf/local.conf</code> configuration in
the <a class="link" href="#build-directory" target="_top">build directory</a>
and then rebuild the image.
With this method, you need to modify the
<a class="link" href="#var-EXTRA_IMAGE_FEATURES" target="_top"><code class="filename">EXTRA_IMAGE_FEATURES</code></a>
variable to have the value of "tools-debug" before rebuilding the image.
Once the image is rebuilt, the <code class="filename">tcf-agent</code> will be included
in the image and is launched automatically after the boot.</p></li><li class="listitem"><p>Manually build the <code class="filename">tcf-agent</code>.
To build the agent, follow these steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Be sure the ADT is installed as described in the
"<a class="link" href="#installing-the-adt" title="2.1. Installing the ADT and Toolchains">Installing the ADT and Toolchains</a>" section.
</p></li><li class="listitem"><p>Set up the cross-development environment as described in the
"<a class="link" href="#setting-up-the-cross-development-environment" title="2.2. Setting Up the Cross-Development Environment">Setting
Up the Cross-Development Environment</a>" section.</p></li><li class="listitem"><p>Get the <code class="filename">tcf-agent</code> source code using
the following commands:
</p><pre class="literallayout">
$ git clone http://git.eclipse.org/gitroot/tcf/org.eclipse.tcf.agent.git
$ cd agent
</pre></li><li class="listitem"><p>Modify the <code class="filename">Makefile.inc</code> file
for the cross-compilation environment by setting the
<code class="filename">OPSYS</code> and
<a class="link" href="#var-MACHINE" target="_top"><code class="filename">MACHINE</code></a>
variables according to your target.</p></li><li class="listitem"><p>Use the cross-development tools to build the
<code class="filename">tcf-agent</code>.
Before you "Make" the file, be sure your cross-tools are set up first.
See the "<a class="link" href="#makefile-based-projects" title="4.2. Makefile-Based Projects">Makefile-Based Projects</a>"
section for information on how to make sure the cross-tools are set up
correctly.</p><p>If the build is successful, the <code class="filename">tcf-agent</code> output will
be <code class="filename">obj/$(OPSYS)/$(MACHINE)/Debug/agent</code>.</p></li><li class="listitem"><p>Deploy the agent into the image's root filesystem.</p></li></ol></div><p>
</p></li></ul></div><p>
</p></div><div class="section" title="2.3.2. Extracting the Root Filesystem"><div class="titlepage"><div><div><h3 class="title"><a id="extracting-the-root-filesystem"></a>2.3.2. Extracting the Root Filesystem</h3></div></div></div><p>
You must extract the root filesystem if you want to boot the image using NFS
or you want to use the root filesystem as the target sysroot.
For example, the Eclipse IDE environment with the Eclipse Yocto Plug-in installed allows you
to use QEMU to boot under NFS.
Another example is if you want to develop your target application using the
root filesystem as the target sysroot.
</p><p>
To extract the root filesystem, first <code class="filename">source</code>
the cross-development environment setup script and then
use the <code class="filename">runqemu-extract-sdk</code> command on the
filesystem image.
For example, the following commands set up the environment and then extract
the root filesystem from a previously built filesystem image tarball named
<code class="filename">core-image-sato-sdk-qemux86-2011091411831.rootfs.tar.bz2</code>.
The example extracts the root filesystem into the <code class="filename">$HOME/qemux86-sato</code>
directory:
</p><pre class="literallayout">
$ source $HOME/poky/build/tmp/environment-setup-i586-poky-linux
$ runqemu-extract-sdk \
tmp/deploy/images/core-image-sato-sdk-qemux86-2011091411831.rootfs.tar.bz2 \
$HOME/qemux86-sato
</pre><p>
In this case, you could now point to the target sysroot at
<code class="filename">$HOME/qemux86-sato</code>.
</p></div></div></div>
<div class="chapter" title="Chapter 3. Optionally Customizing the Development Packages Installation"><div class="titlepage"><div><div><h2 class="title"><a id="adt-package"></a>Chapter 3. Optionally Customizing the Development Packages Installation</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#package-management-systems">3.1. Package Management Systems</a></span></dt><dt><span class="section"><a href="#configuring-the-pms">3.2. Configuring the PMS</a></span></dt></dl></div><p>
Because the Yocto Project is suited for embedded Linux development, it is
likely that you will need to customize your development packages installation.
For example, if you are developing a minimal image, then you might not need
certain packages (e.g. graphics support packages).
Thus, you would like to be able to remove those packages from your target sysroot.
</p><div class="section" title="3.1. Package Management Systems"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="package-management-systems"></a>3.1. Package Management Systems</h2></div></div></div><p>
The OpenEmbedded build system supports the generation of sysroot files using
three different Package Management Systems (PMS):
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>OPKG:</em></span> A less well known PMS whose use
originated in the OpenEmbedded and OpenWrt embedded Linux projects.
This PMS works with files packaged in an <code class="filename">.ipk</code> format.
See <a class="ulink" href="http://en.wikipedia.org/wiki/Opkg" target="_top">http://en.wikipedia.org/wiki/Opkg</a> for more
information about OPKG.</p></li><li class="listitem"><p><span class="emphasis"><em>RPM:</em></span> A more widely known PMS intended for GNU/Linux
distributions.
This PMS works with files packaged in an <code class="filename">.rms</code> format.
The build system currently installs through this PMS by default.
See <a class="ulink" href="http://en.wikipedia.org/wiki/RPM_Package_Manager" target="_top">http://en.wikipedia.org/wiki/RPM_Package_Manager</a>
for more information about RPM.</p></li><li class="listitem"><p><span class="emphasis"><em>Debian:</em></span> The PMS for Debian-based systems
is built on many PMS tools.
The lower-level PMS tool <code class="filename">dpkg</code> forms the base of the Debian PMS.
For information on dpkg see
<a class="ulink" href="http://en.wikipedia.org/wiki/Dpkg" target="_top">http://en.wikipedia.org/wiki/Dpkg</a>.</p></li></ul></div><p>
</p></div><div class="section" title="3.2. Configuring the PMS"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="configuring-the-pms"></a>3.2. Configuring the PMS</h2></div></div></div><p>
Whichever PMS you are using, you need to be sure that the
<a class="link" href="#var-PACKAGE_CLASSES" target="_top"><code class="filename">PACKAGE_CLASSES</code></a>
variable in the <code class="filename">conf/local.conf</code>
file is set to reflect that system.
The first value you choose for the variable specifies the package file format for the root
filesystem at sysroot.
Additional values specify additional formats for convenience or testing.
See the configuration file for details.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
For build performance information related to the PMS, see
<a class="link" href="#ref-classes-package" target="_top">Packaging - <code class="filename">package*.bbclass</code></a>
in the Yocto Project Reference Manual.
</div><p>
As an example, consider a scenario where you are using OPKG and you want to add
the <code class="filename">libglade</code> package to the target sysroot.
</p><p>
First, you should generate the <code class="filename">ipk</code> file for the
<code class="filename">libglade</code> package and add it
into a working <code class="filename">opkg</code> repository.
Use these commands:
</p><pre class="literallayout">
$ bitbake libglade
$ bitbake package-index
</pre><p>
</p><p>
Next, source the environment setup script found in the
<a class="link" href="#source-directory" target="_top">source directory</a>.
Follow that by setting up the installation destination to point to your
sysroot as <code class="filename">&lt;sysroot_dir&gt;</code>.
Finally, have an OPKG configuration file <code class="filename">&lt;conf_file&gt;</code>
that corresponds to the <code class="filename">opkg</code> repository you have just created.
The following command forms should now work:
</p><pre class="literallayout">
$ opkg-cl –f &lt;conf_file&gt; -o &lt;sysroot_dir&gt; update
$ opkg-cl –f &lt;cconf_file&gt; -o &lt;sysroot_dir&gt; \
--force-overwrite install libglade
$ opkg-cl –f &lt;cconf_file&gt; -o &lt;sysroot_dir&gt; \
--force-overwrite install libglade-dbg
$ opkg-cl –f &lt;conf_file&gt; -o &lt;sysroot_dir&gt; \
--force-overwrite install libglade-dev
</pre><p>
</p></div></div>
<div class="chapter" title="Chapter 4. Using the Command Line"><div class="titlepage"><div><div><h2 class="title"><a id="using-the-command-line"></a>Chapter 4. Using the Command Line</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#autotools-based-projects">4.1. Autotools-Based Projects</a></span></dt><dt><span class="section"><a href="#makefile-based-projects">4.2. Makefile-Based Projects</a></span></dt></dl></div><p>
Recall that earlier the manual discussed how to use an existing toolchain
tarball that had been installed into <code class="filename">/opt/poky</code>,
which is outside of the build directory
(see the section "<a class="link" href="#using-an-existing-toolchain-tarball" title="2.1.2. Using a Cross-Toolchain Tarball">Using an Existing
Toolchain Tarball)</a>".
And, that sourcing your architecture-specific environment setup script
initializes a suitable cross-toolchain development environment.
During the setup, locations for the compiler, QEMU scripts, QEMU binary,
a special version of <code class="filename">pkgconfig</code> and other useful
utilities are added to the <code class="filename">PATH</code> variable.
Variables to assist <code class="filename">pkgconfig</code> and <code class="filename">autotools</code>
are also defined so that,
for example, <code class="filename">configure.sh</code> can find pre-generated
test results for tests that need target hardware on which to run.
These conditions allow you to easily use the toolchain outside of the
OpenEmbedded build environment on both autotools-based projects and
Makefile-based projects.
</p><div class="section" title="4.1. Autotools-Based Projects"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="autotools-based-projects"></a>4.1. Autotools-Based Projects</h2></div></div></div><p>
For an Autotools-based project, you can use the cross-toolchain by just
passing the appropriate host option to <code class="filename">configure.sh</code>.
The host option you use is derived from the name of the environment setup
script in <code class="filename">/opt/poky</code> resulting from unpacking the
cross-toolchain tarball.
For example, the host option for an ARM-based target that uses the GNU EABI
is <code class="filename">armv5te-poky-linux-gnueabi</code>.
Note that the name of the script is
<code class="filename">environment-setup-armv5te-poky-linux-gnueabi</code>.
Thus, the following command works:
</p><pre class="literallayout">
$ configure --host=armv5te-poky-linux-gnueabi \
--with-libtool-sysroot=&lt;sysroot-dir&gt;
</pre><p>
</p><p>
This single command updates your project and rebuilds it using the appropriate
cross-toolchain tools.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
If <code class="filename">configure</code> script results in problems recognizing the
<code class="filename">--with-libtool-sysroot=&lt;sysroot-dir&gt;</code> option,
regenerate the script to enable the support by doing the following and then
re-running the script:
<pre class="literallayout">
$ libtoolize --automake
$ aclocal -I ${OECORE_NATIVE_SYSROOT}/usr/share/aclocal \
[-I &lt;dir_containing_your_project-specific_m4_macros&gt;]
$ autoconf
$ autoheader
$ automake -a
</pre></div></div><div class="section" title="4.2. Makefile-Based Projects"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="makefile-based-projects"></a>4.2. Makefile-Based Projects</h2></div></div></div><p>
For a Makefile-based project, you use the cross-toolchain by making sure
the tools are used.
You can do this as follows:
</p><pre class="literallayout">
CC=arm-poky-linux-gnueabi-gcc
LD=arm-poky-linux-gnueabi-ld
CFLAGS=”${CFLAGS} --sysroot=&lt;sysroot-dir&gt;”
CXXFLAGS=”${CXXFLAGS} --sysroot=&lt;sysroot-dir&gt;”
</pre><p>
</p></div></div>
</div>
<table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="100%"><tr><td align="left"><img src="figures/bsp-title.png" align="left" width="100%" /></td></tr></table>
<div xml:lang="en" class="book" lang="en"><div class="titlepage"><div><div><h1 class="title"><a id="bsp-guide"></a></h1></div><div><div class="authorgroup">
<div class="author"><h3 class="author"><span class="firstname">Tom</span> <span class="surname">Zanussi</span></h3><div class="affiliation">
<span class="orgname">Intel Corporation<br /></span>
</div><code class="email">&lt;<a class="email" href="mailto:tom.zanussi@intel.com">tom.zanussi@intel.com</a>&gt;</code></div>
<div class="author"><h3 class="author"><span class="firstname">Richard</span> <span class="surname">Purdie</span></h3><div class="affiliation">
<span class="orgname">Linux Foundation<br /></span>
</div><code class="email">&lt;<a class="email" href="mailto:richard.purdie@linuxfoundation.org">richard.purdie@linuxfoundation.org</a>&gt;</code></div>
</div></div><div><p class="copyright">Copyright © 2010-2012 Linux Foundation</p></div><div><div class="legalnotice" title="Legal Notice"><a id="id1501714"></a>
<p>
Permission is granted to copy, distribute and/or modify this document under
the terms of the <a class="ulink" href="http://creativecommons.org/licenses/by-nc-sa/2.0/uk/" target="_top">Creative Commons Attribution-Non-Commercial-Share Alike 2.0 UK: England &amp; Wales</a> as published by Creative Commons.
</p>
<div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Due to production processes, there could be differences between the Yocto Project
documentation bundled in the release tarball and the
Yocto Project Board Support Package (BSP) Developer's Guide on
the <a class="ulink" href="http://www.yoctoproject.org" target="_top">Yocto Project</a> website.
For the latest version of this manual, see the manual on the website.
</div>
</div></div><div><div class="revhistory"><table border="1" width="100%" summary="Revision history"><tr><th align="left" valign="top" colspan="2"><b>Revision History</b></th></tr>
<tr><td align="left">Revision 0.9</td><td align="left">24 November 2010</td></tr><tr><td align="left" colspan="2">The initial document draft released with the Yocto Project 0.9 Release.</td></tr>
<tr><td align="left">Revision 1.0</td><td align="left">6 April 2011</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.0 Release.</td></tr>
<tr><td align="left">Revision 1.0.1</td><td align="left">23 May 2011</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.0.1 Release.</td></tr>
<tr><td align="left">Revision 1.1</td><td align="left">6 October 2011</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.1 Release.</td></tr>
<tr><td align="left">Revision 1.2</td><td align="left">April 2012</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.2 Release.</td></tr>
<tr><td align="left">Revision 1.3</td><td align="left">Sometime in 2012</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.3 Release.</td></tr>
</table></div></div></div><hr /></div>
<div class="chapter" title="Chapter 1. Board Support Packages (BSP) - Developer's Guide"><div class="titlepage"><div><div><h2 class="title"><a id="bsp"></a>Chapter 1. Board Support Packages (BSP) - Developer's Guide</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#bsp-layers">1.1. BSP Layers</a></span></dt><dt><span class="section"><a href="#bsp-filelayout">1.2. Example Filesystem Layout</a></span></dt><dd><dl><dt><span class="section"><a href="#bsp-filelayout-license">1.2.1. License Files</a></span></dt><dt><span class="section"><a href="#bsp-filelayout-readme">1.2.2. README File</a></span></dt><dt><span class="section"><a href="#bsp-filelayout-readme-sources">1.2.3. README.sources File</a></span></dt><dt><span class="section"><a href="#bsp-filelayout-binary">1.2.4. Pre-built User Binaries</a></span></dt><dt><span class="section"><a href="#bsp-filelayout-layer">1.2.5. Layer Configuration File</a></span></dt><dt><span class="section"><a href="#bsp-filelayout-machine">1.2.6. Hardware Configuration Options</a></span></dt><dt><span class="section"><a href="#bsp-filelayout-misc-recipes">1.2.7. Miscellaneous Recipe Files</a></span></dt><dt><span class="section"><a href="#bsp-filelayout-core-recipes">1.2.8. Core Recipe Files</a></span></dt><dt><span class="section"><a href="#bsp-filelayout-recipes-graphics">1.2.9. Display Support Files</a></span></dt><dt><span class="section"><a href="#bsp-filelayout-kernel">1.2.10. Linux Kernel Configuration</a></span></dt></dl></dd><dt><span class="section"><a href="#requirements-and-recommendations-for-released-bsps">1.3. Requirements and Recommendations for Released BSPs</a></span></dt><dd><dl><dt><span class="section"><a href="#released-bsp-requirements">1.3.1. Released BSP Requirements</a></span></dt><dt><span class="section"><a href="#released-bsp-recommendations">1.3.2. Released BSP Recommendations</a></span></dt></dl></dd><dt><span class="section"><a href="#customizing-a-recipe-for-a-bsp">1.4. Customizing a Recipe for a BSP</a></span></dt><dt><span class="section"><a href="#bsp-licensing-considerations">1.5. BSP Licensing Considerations</a></span></dt><dt><span class="section"><a href="#using-the-yocto-projects-bsp-tools">1.6. Using the Yocto Project's BSP Tools</a></span></dt><dd><dl><dt><span class="section"><a href="#common-features">1.6.1. Common Features</a></span></dt><dt><span class="section"><a href="#creating-a-new-bsp-layer-using-the-yocto-bsp-script">1.6.2. Creating a new BSP Layer Using the yocto-bsp Script</a></span></dt><dt><span class="section"><a href="#managing-kernel-patches-and-config-items-with-yocto-kernel">1.6.3. Managing Kernel Patches and Config Items with yocto-kernel</a></span></dt></dl></dd></dl></div><p>
A Board Support Package (BSP) is a collection of information that
defines how to support a particular hardware device, set of devices, or
hardware platform.
The BSP includes information about the hardware features
present on the device and kernel configuration information along with any
additional hardware drivers required.
The BSP also lists any additional software
components required in addition to a generic Linux software stack for both
essential and optional platform features.
</p><p>
This chapter (or document if you are reading the BSP Developer's Guide)
talks about BSP Layers, defines a structure for components
so that BSPs follow a commonly understood layout, discusses how to customize
a recipe for a BSP, addresses BSP licensing, and provides information that
shows you how to create and manage a
<a class="link" href="#bsp-layers" title="1.1. BSP Layers">BSP Layer</a> using two Yocto Project
<a class="link" href="#using-the-yocto-projects-bsp-tools" title="1.6. Using the Yocto Project's BSP Tools">BSP Tools</a>.
</p><div class="section" title="1.1. BSP Layers"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="bsp-layers"></a>1.1. BSP Layers</h2></div></div></div><p>
The BSP consists of a file structure inside a base directory.
Collectively, you can think of the base directory and the file structure
as a BSP Layer.
BSP Layers use the following naming convention:
</p><pre class="literallayout">
meta-&lt;bsp_name&gt;
</pre><p>
"bsp_name" is a placeholder for the machine or platform name.
</p><p>
The layer's base directory (<code class="filename">meta-&lt;bsp_name&gt;</code>) is the root
of the BSP Layer.
This root is what you add to the
<a class="link" href="#var-BBLAYERS" target="_top"><code class="filename">BBLAYERS</code></a>
variable in the <code class="filename">conf/bblayers.conf</code> file found in the
<a class="link" href="#build-directory" target="_top">build directory</a>.
Adding the root allows the OpenEmbedded build system to recognize the BSP
definition and from it build an image.
Here is an example:
</p><pre class="literallayout">
BBLAYERS = " \
/usr/local/src/yocto/meta \
/usr/local/src/yocto/meta-yocto \
/usr/local/src/yocto/meta-&lt;bsp_name&gt; \
"
</pre><p>
</p><p>
Some BSPs require additional layers on
top of the BSP's root layer in order to be functional.
For these cases, you also need to add those layers to the
<code class="filename">BBLAYERS</code> variable in order to build the BSP.
You must also specify in the "Dependencies" section of the BSP's
<code class="filename">README</code> file any requirements for additional
layers and, preferably, any
build instructions that might be contained elsewhere
in the <code class="filename">README</code> file.
</p><p>
Some layers function as a layer to hold other BSP layers.
An example of this type of layer is the <code class="filename">meta-intel</code> layer.
The <code class="filename">meta-intel</code> layer contains over 10 individual BSP layers.
</p><p>
For more detailed information on layers, see the
"<a class="link" href="#understanding-and-creating-layers" target="_top">Understanding and Creating Layers</a>"
section of the Yocto Project Development Manual.
You can also see the detailed examples in the appendices of the
Yocto Project Development Manual.
</p></div><div class="section" title="1.2. Example Filesystem Layout"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="bsp-filelayout"></a>1.2. Example Filesystem Layout</h2></div></div></div><p>
Providing a common form allows end-users to understand and become familiar
with the layout.
A common format also encourages standardization of software support of hardware.
</p><p>
The proposed form does have elements that are specific to the
OpenEmbedded build system.
It is intended that this information can be
used by other build systems besides the OpenEmbedded build system
and that it will be simple
to extract information and convert it to other formats if required.
The OpenEmbedded build system, through its standard layers mechanism, can directly
accept the format described as a layer.
The BSP captures all
the hardware-specific details in one place in a standard format, which is
useful for any person wishing to use the hardware platform regardless of
the build system they are using.
</p><p>
The BSP specification does not include a build system or other tools -
it is concerned with the hardware-specific components only.
At the end-distribution point, you can ship the BSP combined with a build system
and other tools.
However, it is important to maintain the distinction that these
are separate components that happen to be combined in certain end products.
</p><p>
Before looking at the common form for the file structure inside a BSP Layer,
you should be aware that some requirements do exist in order for a BSP to
be considered compliant with the Yocto Project.
For that list of requirements, see the
"<a class="link" href="#released-bsp-requirements" title="1.3.1. Released BSP Requirements">Released BSP Requirements</a>"
section.
</p><p>
Below is the common form for the file structure inside a BSP Layer.
While you can use this basic form for the standard, realize that the actual structures
for specific BSPs could differ.
</p><pre class="literallayout">
meta-&lt;bsp_name&gt;/
meta-&lt;bsp_name&gt;/&lt;bsp_license_file&gt;
meta-&lt;bsp_name&gt;/README
meta-&lt;bsp_name&gt;/README.sources
meta-&lt;bsp_name&gt;/binary/&lt;bootable_images&gt;
meta-&lt;bsp_name&gt;/conf/layer.conf
meta-&lt;bsp_name&gt;/conf/machine/*.conf
meta-&lt;bsp_name&gt;/recipes-bsp/*
meta-&lt;bsp_name&gt;/recipes-core/*
meta-&lt;bsp_name&gt;/recipes-graphics/*
meta-&lt;bsp_name&gt;/recipes-kernel/linux/linux-yocto_&lt;kernel_rev&gt;.bbappend
</pre><p>
</p><p>
Below is an example of the Crown Bay BSP:
</p><pre class="literallayout">
meta-crownbay/COPYING.MIT
meta-crownbay/README
meta-crownbay/README.sources
meta-crownbay/binary/
meta-crownbay/conf/
meta-crownbay/conf/layer.conf
meta-crownbay/conf/machine/
meta-crownbay/conf/machine/crownbay.conf
meta-crownbay/conf/machine/crownbay-noemgd.conf
meta-crownbay/recipes-bsp/
meta-crownbay/recipes-bsp/formfactor/
meta-crownbay/recipes-bsp/formfactor/formfactor_0.0.bbappend
meta-crownbay/recipes-bsp/formfactor/formfactor/
meta-crownbay/recipes-bsp/formfactor/formfactor/crownbay/
meta-crownbay/recipes-bsp/formfactor/formfactor/crownbay/machconfig
meta-crownbay/recipes-bsp/formfactor/formfactor/crownbay-noemgd/
meta-crownbay/recipes-bsp/formfactor/formfactor/crownbay-noemgd/machconfig
meta-crownbay/recipes-core/
meta-crownbay/recipes-core/tasks/
meta-crownbay/recipes-core/tasks/task-core-tools-profile.bbappend
meta-crownbay/recipes-graphics/
meta-crownbay/recipes-graphics/xorg-xserver/
meta-crownbay/recipes-graphics/xorg-xserver/xserver-xf86-config_0.1.bbappend
meta-crownbay/recipes-graphics/xorg-xserver/xserver-xf86-config/
meta-crownbay/recipes-graphics/xorg-xserver/xserver-xf86-config/crownbay/
meta-crownbay/recipes-graphics/xorg-xserver/xserver-xf86-config/crownbay/xorg.conf
meta-crownbay/recipes-graphics/xorg-xserver/xserver-xf86-config/crownbay-noemgd/
meta-crownbay/recipes-graphics/xorg-xserver/xserver-xf86-config/crownbay-noemgd/xorg.conf
meta-crownbay/recipes-kernel/
meta-crownbay/recipes-kernel/linux/
meta-crownbay/recipes-kernel/linux/linux-yocto-rt_3.0.bbappend
meta-crownbay/recipes-kernel/linux/linux-yocto_2.6.37.bbappend
meta-crownbay/recipes-kernel/linux/linux-yocto_3.0.bbappend
</pre><p>
</p><p>
The following sections describe each part of the proposed BSP format.
</p><div class="section" title="1.2.1. License Files"><div class="titlepage"><div><div><h3 class="title"><a id="bsp-filelayout-license"></a>1.2.1. License Files</h3></div></div></div><p>
You can find these files in the BSP Layer at:
</p><pre class="literallayout">
meta-&lt;bsp_name&gt;/&lt;bsp_license_file&gt;
</pre><p>
</p><p>
These optional files satisfy licensing requirements for the BSP.
The type or types of files here can vary depending on the licensing requirements.
For example, in the Crown Bay BSP all licensing requirements are handled with the
<code class="filename">COPYING.MIT</code> file.
</p><p>
Licensing files can be MIT, BSD, GPLv*, and so forth.
These files are recommended for the BSP but are optional and totally up to the BSP developer.
</p></div><div class="section" title="1.2.2. README File"><div class="titlepage"><div><div><h3 class="title"><a id="bsp-filelayout-readme"></a>1.2.2. README File</h3></div></div></div><p>
You can find this file in the BSP Layer at:
</p><pre class="literallayout">
meta-&lt;bsp_name&gt;/README
</pre><p>
</p><p>
This file provides information on how to boot the live images that are optionally
included in the <code class="filename">binary/</code> directory.
The <code class="filename">README</code> file also provides special information needed for
building the image.
</p><p>
At a minimum, the <code class="filename">README</code> file must
contain a list of dependencies, such as the names of
any other layers on which the BSP depends and the name of
the BSP maintainer with his or her contact information.
</p></div><div class="section" title="1.2.3. README.sources File"><div class="titlepage"><div><div><h3 class="title"><a id="bsp-filelayout-readme-sources"></a>1.2.3. README.sources File</h3></div></div></div><p>
You can find this file in the BSP Layer at:
</p><pre class="literallayout">
meta-&lt;bsp_name&gt;/README.sources
</pre><p>
</p><p>
This file provides information on where to locate the BSP source files.
For example, information provides where to find the sources that comprise
the images shipped with the BSP.
Information is also included to help you find the metadata used to generate the images
that ship with the BSP.
</p></div><div class="section" title="1.2.4. Pre-built User Binaries"><div class="titlepage"><div><div><h3 class="title"><a id="bsp-filelayout-binary"></a>1.2.4. Pre-built User Binaries</h3></div></div></div><p>
You can find these files in the BSP Layer at:
</p><pre class="literallayout">
meta-&lt;bsp_name&gt;/binary/&lt;bootable_images&gt;
</pre><p>
</p><p>
This optional area contains useful pre-built kernels and user-space filesystem
images appropriate to the target system.
This directory typically contains graphical (e.g. sato) and minimal live images
when the BSP tarball has been created and made available in the
<a class="ulink" href="http://www.yoctoproject.org" target="_top">Yocto Project</a> website.
You can use these kernels and images to get a system running and quickly get started
on development tasks.
</p><p>
The exact types of binaries present are highly hardware-dependent.
However, a README file should be present in the BSP Layer that explains how to use
the kernels and images with the target hardware.
If pre-built binaries are present, source code to meet licensing requirements must also
exist in some form.
</p></div><div class="section" title="1.2.5. Layer Configuration File"><div class="titlepage"><div><div><h3 class="title"><a id="bsp-filelayout-layer"></a>1.2.5. Layer Configuration File</h3></div></div></div><p>
You can find this file in the BSP Layer at:
</p><pre class="literallayout">
meta-&lt;bsp_name&gt;/conf/layer.conf
</pre><p>
</p><p>
The <code class="filename">conf/layer.conf</code> file identifies the file structure as a
layer, identifies the
contents of the layer, and contains information about how the build
system should use it.
Generally, a standard boilerplate file such as the following works.
In the following example, you would replace "<code class="filename">bsp</code>" and
"<code class="filename">_bsp</code>" with the actual name
of the BSP (i.e. <code class="filename">&lt;bsp_name&gt;</code> from the example template).
</p><p>
</p><pre class="literallayout">
# We have a conf and classes directory, add to BBPATH
BBPATH := "${BBPATH}:${LAYERDIR}"
# We have a recipes directory, add to BBFILES
BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*.bb \
${LAYERDIR}/recipes-*/*.bbappend"
BBFILE_COLLECTIONS += "bsp"
BBFILE_PATTERN_bsp := "^${LAYERDIR}/"
BBFILE_PRIORITY_bsp = "6"
</pre><p>
</p><p>
To illustrate the string substitutions, here are the last three statements from the Crown
Bay <code class="filename">conf/layer.conf</code> file:
</p><pre class="literallayout">
BBFILE_COLLECTIONS += "crownbay"
BBFILE_PATTERN_crownbay := "^${LAYERDIR}/"
BBFILE_PRIORITY_crownbay = "6"
</pre><p>
</p><p>
This file simply makes BitBake aware of the recipes and configuration directories.
The file must exist so that the OpenEmbedded build system can recognize the BSP.
</p></div><div class="section" title="1.2.6. Hardware Configuration Options"><div class="titlepage"><div><div><h3 class="title"><a id="bsp-filelayout-machine"></a>1.2.6. Hardware Configuration Options</h3></div></div></div><p>
You can find these files in the BSP Layer at:
</p><pre class="literallayout">
meta-&lt;bsp_name&gt;/conf/machine/*.conf
</pre><p>
</p><p>
The machine files bind together all the information contained elsewhere
in the BSP into a format that the build system can understand.
If the BSP supports multiple machines, multiple machine configuration files
can be present.
These filenames correspond to the values to which users have set the
<a class="link" href="#var-MACHINE" target="_top"><code class="filename">MACHINE</code></a> variable.
</p><p>
These files define things such as the kernel package to use
(<a class="link" href="#var-PREFERRED_PROVIDER" target="_top"><code class="filename">PREFERRED_PROVIDER</code></a>
of virtual/kernel), the hardware drivers to
include in different types of images, any special software components
that are needed, any bootloader information, and also any special image
format requirements.
</p><p>
Each BSP Layer requires at least one machine file.
However, you can supply more than one file.
For example, in the Crown Bay BSP shown earlier in this section, the
<code class="filename">conf/machine</code> directory contains two configuration files:
<code class="filename">crownbay.conf</code> and <code class="filename">crownbay-noemgd.conf</code>.
The <code class="filename">crownbay.conf</code> file is used for the Crown Bay BSP
that supports the <span class="trademark">Intel</span>® Embedded
Media and Graphics Driver (<span class="trademark">Intel</span>®
EMGD), while the <code class="filename">crownbay-noemgd.conf</code> file is used for the
Crown Bay BSP that does not support the <span class="trademark">Intel</span>®
EMGD.
</p><p>
This <code class="filename">crownbay.conf</code> file could also include
a hardware "tuning" file that is commonly used to
define the package architecture and specify
optimization flags, which are carefully chosen to give best
performance on a given processor.
</p><p>
Tuning files are found in the <code class="filename">meta/conf/machine/include</code>
directory within the
<a class="link" href="#source-directory" target="_top">source directory</a>.
Tuning files can also reside in the BSP Layer itself.
For example, the <code class="filename">ia32-base.inc</code> file resides in the
<code class="filename">meta-intel</code> BSP Layer in <code class="filename">conf/machine/include</code>.
</p><p>
To use an include file, you simply include them in the machine configuration file.
For example, the Crown Bay BSP <code class="filename">crownbay.conf</code> has the
following statements:
</p><pre class="literallayout">
include conf/machine/include/tune-atom.inc
include conf/machine/include/ia32-base.inc
</pre><p>
</p></div><div class="section" title="1.2.7. Miscellaneous Recipe Files"><div class="titlepage"><div><div><h3 class="title"><a id="bsp-filelayout-misc-recipes"></a>1.2.7. Miscellaneous Recipe Files</h3></div></div></div><p>
You can find these files in the BSP Layer at:
</p><pre class="literallayout">
meta-&lt;bsp_name&gt;/recipes-bsp/*
</pre><p>
</p><p>
This optional directory contains miscellaneous recipe files for the BSP.
Most notably would be the formfactor files.
For example, in the Crown Bay BSP there is the
<code class="filename">formfactor_0.0.bbappend</code> file, which is an append file used
to augment the recipe that starts the build.
Furthermore, there are machine-specific settings used during the build that are
defined by the <code class="filename">machconfig</code> files.
In the Crown Bay example, two <code class="filename">machconfig</code> files exist:
one that supports the
<span class="trademark">Intel</span>® Embedded
Media and Graphics Driver (<span class="trademark">Intel</span>®
EMGD) and one that does not:
</p><pre class="literallayout">
meta-crownbay/recipes-bsp/formfactor/formfactor/crownbay/machconfig
meta-crownbay/recipes-bsp/formfactor/formfactor/crownbay-noemgd/machconfig
meta-crownbay/recipes-bsp/formfactor/formfactor_0.0.bbappend
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
If a BSP does not have a formfactor entry, defaults are established according to
the formfactor configuration file that is installed by the main
formfactor recipe
<code class="filename">meta/recipes-bsp/formfactor/formfactor_0.0.bb</code>,
which is found in the
<a class="link" href="#source-directory" target="_top">source directory</a>.
</p></div></div><div class="section" title="1.2.8. Core Recipe Files"><div class="titlepage"><div><div><h3 class="title"><a id="bsp-filelayout-core-recipes"></a>1.2.8. Core Recipe Files</h3></div></div></div><p>
You can find these files in the BSP Layer at:
</p><pre class="literallayout">
meta-&lt;bsp_name&gt;/recipes-core/*
</pre><p>
</p><p>
This directory contains recipe files that are almost always necessary to build a
useful, working Linux image.
Thus, the term "core" is used to group these recipes.
For example, in the Crown Bay BSP there is the
<code class="filename">task-core-tools-profile.bbappend</code> file, which is an append file used
to recommend that the
<a class="ulink" href="http://sourceware.org/systemtap/wiki" target="_top">SystemTap</a>
package be included as a package when the image is built.
</p></div><div class="section" title="1.2.9. Display Support Files"><div class="titlepage"><div><div><h3 class="title"><a id="bsp-filelayout-recipes-graphics"></a>1.2.9. Display Support Files</h3></div></div></div><p>
You can find these files in the BSP Layer at:
</p><pre class="literallayout">
meta-&lt;bsp_name&gt;/recipes-graphics/*
</pre><p>
</p><p>
This optional directory contains recipes for the BSP if it has
special requirements for graphics support.
All files that are needed for the BSP to support a display are kept here.
For example, the Crown Bay BSP contains two versions of the
<code class="filename">xorg.conf</code> file.
The version in <code class="filename">crownbay</code> builds a BSP that supports the
<span class="trademark">Intel</span>® Embedded Media Graphics Driver (EMGD),
while the version in <code class="filename">crownbay-noemgd</code> builds
a BSP that supports Video Electronics Standards Association (VESA) graphics only:
</p><pre class="literallayout">
meta-crownbay/recipes-graphics/xorg-xserver/xserver-xf86-config_0.1.bbappend
meta-crownbay/recipes-graphics/xorg-xserver/xserver-xf86-config/crownbay/xorg.conf
meta-crownbay/recipes-graphics/xorg-xserver/xserver-xf86-config/crownbay-noemgd/xorg.conf
</pre><p>
</p></div><div class="section" title="1.2.10. Linux Kernel Configuration"><div class="titlepage"><div><div><h3 class="title"><a id="bsp-filelayout-kernel"></a>1.2.10. Linux Kernel Configuration</h3></div></div></div><p>
You can find these files in the BSP Layer at:
</p><pre class="literallayout">
meta-&lt;bsp_name&gt;/recipes-kernel/linux/linux-yocto_*.bbappend
</pre><p>
</p><p>
These files append your specific changes to the main kernel recipe you are using.
</p><p>
For your BSP, you typically want to use an existing Yocto Project kernel recipe found in the
<a class="link" href="#source-directory" target="_top">source directory</a>
at <code class="filename">meta/recipes-kernel/linux</code>.
You can append your specific changes to the kernel recipe by using a
similarly named append file, which is located in the BSP Layer (e.g.
the <code class="filename">meta-&lt;bsp_name&gt;/recipes-kernel/linux</code> directory).
</p><p>
Suppose you are using the <code class="filename">linux-yocto_3.4.bb</code> recipe to build
the kernel.
In other words, you have selected the kernel in your
<code class="filename">&lt;bsp_name&gt;.conf</code> file by adding the following statements:
</p><pre class="literallayout">
PREFERRED_PROVIDER_virtual/kernel ?= "linux-yocto"
PREFERRED_VERSION_linux-yocto = "3.4%"
</pre><p>
You would use the <code class="filename">linux-yocto_3.4.bbappend</code> file to append
specific BSP settings to the kernel, thus configuring the kernel for your particular BSP.
</p><p>
As an example, look at the existing Crown Bay BSP.
The append file used is:
</p><pre class="literallayout">
meta-crownbay/recipes-kernel/linux/linux-yocto_3.4.bbappend
</pre><p>
The following listing shows the file.
Be aware that the actual commit ID strings in this example listing might be different
than the actual strings in the file from the <code class="filename">meta-intel</code>
Git source repository.
</p><pre class="literallayout">
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
COMPATIBLE_MACHINE_crownbay = "crownbay"
KMACHINE_crownbay = "crownbay"
KBRANCH_crownbay = "standard/default/crownbay"
COMPATIBLE_MACHINE_crownbay-noemgd = "crownbay-noemgd"
KMACHINE_crownbay-noemgd = "crownbay"
KBRANCH_crownbay-noemgd = "standard/default/crownbay"
SRCREV_machine_pn-linux-yocto_crownbay ?= "48101e609711fcfe8d5e737a37a5a69f4bd57d9a"
SRCREV_meta_pn-linux-yocto_crownbay ?= "5b4c9dc78b5ae607173cc3ddab9bce1b5f78129b"
SRCREV_machine_pn-linux-yocto_crownbay-noemgd ?= "48101e609711fcfe8d5e737a37a5a69f4bd57d9a"
SRCREV_meta_pn-linux-yocto_crownbay-noemgd ?= "5b4c9dc78b5ae607173cc3ddab9bce1b5f78129b"
</pre><p>
This append file contains statements used to support the Crown Bay BSP for both
<span class="trademark">Intel</span>® EMGD and the VESA graphics.
The build process, in this case, recognizes and uses only the statements that
apply to the defined machine name - <code class="filename">crownbay</code> in this case.
So, the applicable statements in the <code class="filename">linux-yocto_3.4.bbappend</code>
file are follows:
</p><pre class="literallayout">
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
COMPATIBLE_MACHINE_crownbay = "crownbay"
KMACHINE_crownbay = "crownbay"
KBRANCH_crownbay = "standard/default/crownbay"
SRCREV_machine_pn-linux-yocto_crownbay ?= "48101e609711fcfe8d5e737a37a5a69f4bd57d9a"
SRCREV_meta_pn-linux-yocto_crownbay ?= "5b4c9dc78b5ae607173cc3ddab9bce1b5f78129b"
</pre><p>
The append file defines <code class="filename">crownbay</code> as the
<a class="link" href="#var-COMPATIBLE_MACHINE" target="_top"><code class="filename">COMPATIBLE_MACHINE</code></a>
and uses the
<a class="link" href="#var-KMACHINE" target="_top"><code class="filename">KMACHINE</code></a> variable to
ensure the machine name used by the OpenEmbedded build system maps to the
machine name used by the Linux Yocto kernel.
The file also uses the optional
<a class="link" href="#var-KBRANCH" target="_top"><code class="filename">KBRANCH</code></a> variable
to ensure the build process uses the <code class="filename">standard/default/crownbay</code>
kernel branch.
Finally, the append file points to the specific top commits in the
<a class="link" href="#source-directory" target="_top">source directory</a> Git
repository and the <code class="filename">meta</code> Git repository branches to identify the
exact kernel needed to build the Crown Bay BSP.
</p><p>
One thing missing in this particular BSP, which you will typically need when
developing a BSP, is the kernel configuration file (<code class="filename">.config</code>) for your BSP.
When developing a BSP, you probably have a kernel configuration file or a set of kernel
configuration files that, when taken together, define the kernel configuration for your BSP.
You can accomplish this definition by putting the configurations in a file or a set of files
inside a directory located at the same level as your kernel's append file and having the same
name as the kernel's main recipe file.
With all these conditions met, simply reference those files in a
<code class="filename">SRC_URI</code> statement in the append file.
</p><p>
For example, suppose you had a some configuration options in a file called
<code class="filename">network_configs.cfg</code>.
You can place that file inside a directory named <code class="filename">/linux-yocto</code> and then add
a <code class="filename">SRC_URI</code> statement such as the following to the append file.
When the OpenEmbedded build system builds the kernel, the configuration options are
picked up and applied.
</p><pre class="literallayout">
SRC_URI += "file://network_configs.cfg"
</pre><p>
</p><p>
To group related configurations into multiple files, you perform a similar procedure.
Here is an example that groups separate configurations specifically for Ethernet and graphics
into their own files and adds the configurations
by using a <code class="filename">SRC_URI</code> statement like the following in your append file:
</p><pre class="literallayout">
SRC_URI += "file://myconfig.cfg \
file://eth.cfg \
file://gfx.cfg"
</pre><p>
</p><p>
The <code class="filename">FILESEXTRAPATHS</code> variable is in boilerplate form in the
previous example in order to make it easy to do that.
This variable must be in your layer or BitBake will not find the patches or
configurations even if you have them in your <code class="filename">SRC_URI</code>.
The <code class="filename">FILESEXTRAPATHS</code> variable enables the build process to
find those configuration files.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
Other methods exist to accomplish grouping and defining configuration options.
For example, if you are working with a local clone of the kernel repository,
you could checkout the kernel's <code class="filename">meta</code> branch, make your changes,
and then push the changes to the local bare clone of the kernel.
The result is that you directly add configuration options to the
<code class="filename">meta</code> branch for your BSP.
The configuration options will likely end up in that location anyway if the BSP gets
added to the Yocto Project.
For an example showing how to change the BSP configuration, see the
"<a class="link" href="#changing-the-bsp-configuration" target="_top">Changing the BSP Configuration</a>"
section in the Yocto Project Development Manual.
For a better understanding of working with a local clone of the kernel repository
and a local bare clone of the kernel, see the
"<a class="link" href="#modifying-the-kernel-source-code" target="_top">Modifying the Kernel
Source Code</a>" section also in the Yocto Project Development Manual.
</p><p>
In general, however, the Yocto Project maintainers take care of moving the
<code class="filename">SRC_URI</code>-specified
configuration options to the kernel's <code class="filename">meta</code> branch.
Not only is it easier for BSP developers to not have to worry about putting those
configurations in the branch, but having the maintainers do it allows them to apply
'global' knowledge about the kinds of common configuration options multiple BSPs in
the tree are typically using.
This allows for promotion of common configurations into common features.
</p></div></div></div><div class="section" title="1.3. Requirements and Recommendations for Released BSPs"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="requirements-and-recommendations-for-released-bsps"></a>1.3. Requirements and Recommendations for Released BSPs</h2></div></div></div><p>
Certain requirements exist for a released BSP to be considered
compliant with the Yocto Project.
Additionally, a single recommendation also exists.
This section describes the requirements and recommendation for
released BSPs.
</p><div class="section" title="1.3.1. Released BSP Requirements"><div class="titlepage"><div><div><h3 class="title"><a id="released-bsp-requirements"></a>1.3.1. Released BSP Requirements</h3></div></div></div><p>
Before looking at BSP requirements, you should consider the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>The requirements here assume the BSP layer is a well-formed, "legal"
layer that can be added to the Yocto Project.
For guidelines on creating a layer that meets these base requirements, see the
"<a class="link" href="#bsp-layers" title="1.1. BSP Layers">BSP Layers</a>" and the
"<a class="link" href="#understanding-and-creating-layers" target="_top">Understanding
and Creating Layers"</a> in the Yocto Project Development Manual.</p></li><li class="listitem"><p>The requirements in this section apply regardless of how you
ultimately package a BSP.
You should consult the packaging and distribution guidelines for your
specific release process.
For an example of packaging and distribution requirements, see the
<a class="ulink" href="https://wiki.yoctoproject.org/wiki/Third_Party_BSP_Release_Process" target="_top">Third
Party BSP Release Process</a> wiki page.</p></li><li class="listitem"><p>The requirements for the BSP as it is made available to a developer
are completely independent of the released form of the BSP.
For example, the BSP metadata can be contained within a Git repository
and could have a directory structure completely different from what appears
in the officially released BSP layer.</p></li><li class="listitem"><p>It is not required that specific packages or package
modifications exist in the BSP layer, beyond the requirements for general
compliance with the Yocto Project.
For example, no requirement exists dictating that a specific kernel or
kernel version be used in a given BSP.</p></li></ul></div><p>
</p><p>
Following are the requirements for a released BSP that conforms to the
Yocto Project:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Layer Name:</em></span>
The BSP must have a layer name that follows the Yocto
Project standards.
For information on BSP layer names, see the
"<a class="link" href="#bsp-layers" title="1.1. BSP Layers">BSP Layers</a>" section.
</p></li><li class="listitem"><p><span class="emphasis"><em>File System Layout:</em></span>
When possible, use the same directory names in your
BSP layer as listed in the <code class="filename">recipes.txt</code> file.
In particular, you should place recipes
(<code class="filename">.bb</code> files) and recipe
modifications (<code class="filename">.bbappend</code> files) into
<code class="filename">recipes-*</code> subdirectories by functional area
as outlined in <code class="filename">recipes.txt</code>.
If you cannot find a category in <code class="filename">recipes.txt</code>
to fit a particular recipe, you can make up your own
<code class="filename">recipe-*</code> subdirectory.
You can find <code class="filename">recipes.txt</code> in the
<code class="filename">meta</code> directory of the
<a class="link" href="#source-directory" target="_top">source directory</a>,
or in the OpenEmbedded Core Layer
(<code class="filename">openembedded-core</code>) found at
<a class="ulink" href="http://git.openembedded.org/openembedded-core/tree/meta" target="_top">http://git.openembedded.org/openembedded-core/tree/meta</a>.
</p><p>Within any particular <code class="filename">recipes-*</code> category, the layout
should match what is found in the OpenEmbedded Core
Git repository (<code class="filename">openembedded-core</code>)
or the source directory (<code class="filename">poky</code>).
In other words, make sure you place related files in appropriately
related <code class="filename">recipes-*</code> subdirectories specific to the
recipe's function, or within a subdirectory containing a set of closely-related
recipes.
The recipes themselves should follow the general guidelines
for recipes used in the Yocto Project found in the
<a class="ulink" href="https://wiki.yoctoproject.org/wiki/Recipe_%26_Patch_Style_Guide" target="_top">Yocto
Recipe and Patch Style Guide</a>.</p></li><li class="listitem"><p><span class="emphasis"><em>License File:</em></span>
You must include a license file in the
<code class="filename">meta-&lt;bsp_name&gt;</code> directory.
This license covers the BSP metadata as a whole.
You must specify which license to use since there is no
default license if one is not specified.
See the
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi/meta-intel/tree/meta-fishriver/COPYING.MIT" target="_top"><code class="filename">COPYING.MIT</code></a>
file for the Fish River BSP in the <code class="filename">meta-fishriver</code> BSP layer
as an example.</p></li><li class="listitem"><p><span class="emphasis"><em>README File:</em></span>
You must include a <code class="filename">README</code> file in the
<code class="filename">meta-&lt;bsp_name&gt;</code> directory.
See the
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi/meta-intel/tree/meta-fishriver/README" target="_top"><code class="filename">README</code></a>
file for the Fish River BSP in the <code class="filename">meta-fishriver</code> BSP layer
as an example.</p><p>At a minimum, the <code class="filename">README</code> file should
contain the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="circle"><li class="listitem"><p>A brief description about the hardware the BSP
targets.</p></li><li class="listitem"><p>A list of all the dependencies a
on which a BSP layer depends.
These dependencies are typically a list of required layers needed
to build the BSP.
However, the dependencies should also contain information regarding
any other dependencies the BSP might have.</p></li><li class="listitem"><p>Any required special licensing information.
For example, this information includes information on
special variables needed to satisfy a EULA,
or instructions on information needed to build or distribute
binaries built from the BSP metadata.</p></li><li class="listitem"><p>The name and contact information for the
BSP layer maintainer.
This is the person to whom patches and questions should
be sent.</p></li><li class="listitem"><p>Instructions on how to build the BSP using the BSP
layer.</p></li><li class="listitem"><p>Instructions on how to boot the BSP build from
the BSP layer.</p></li><li class="listitem"><p>Instructions on how to boot the binary images
contained in the <code class="filename">/binary</code> directory,
if present.</p></li><li class="listitem"><p>Information on any known bugs or issues that users
should know about when either building or booting the BSP
binaries.</p></li></ul></div></li><li class="listitem"><p><span class="emphasis"><em>README.sources File:</em></span>
You must include a <code class="filename">README.sources</code> in the
<code class="filename">meta-&lt;bsp_name&gt;</code> directory.
This file specifies exactly where you can find the sources used to
generate the binary images contained in the
<code class="filename">/binary</code> directory, if present.
See the
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi/meta-intel/tree/meta-fishriver/README.sources" target="_top"><code class="filename">README.sources</code></a>
file for the Fish River BSP in the <code class="filename">meta-fishriver</code> BSP layer
as an example.</p></li><li class="listitem"><p><span class="emphasis"><em>Layer Configuration File:</em></span>
You must include a <code class="filename">conf/layer.conf</code> in the
<code class="filename">meta-&lt;bsp_name&gt;</code> directory.
This file identifies the <code class="filename">meta-&lt;bsp_name&gt;</code>
BSP layer as a layer to the build system.</p></li><li class="listitem"><p><span class="emphasis"><em>Machine Configuration File:</em></span>
You must include a <code class="filename">conf/machine/&lt;bsp_name&gt;.conf</code>
in the <code class="filename">meta-&lt;bsp_name&gt;</code> directory.
This configuration file defines a machine target that can be built
using the BSP layer.
Multiple machine configuration files define variations of machine
configurations that are supported by the BSP.
If a BSP supports more multiple machine variations, you need to
adequately describe each variation in the BSP
<code class="filename">README</code> file.
Do not use multiple machine configuration files to describe disparate
hardware.
Multiple machine configuration files should describe very similar targets.
If you do have very different targets, you should create a separate
BSP.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>It is completely possible for a developer to structure the
working repository as a conglomeration of unrelated BSP
files, and to possibly generate specifically targeted 'release' BSPs
from that directory using scripts or some other mechanism.
Such considerations are outside the scope of this document.</div><p>
</p></li></ul></div><p>
</p></div><div class="section" title="1.3.2. Released BSP Recommendations"><div class="titlepage"><div><div><h3 class="title"><a id="released-bsp-recommendations"></a>1.3.2. Released BSP Recommendations</h3></div></div></div><p>
Following are recommendations for a released BSP that conforms to the
Yocto Project:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Bootable Images:</em></span>
BSP releases
can contain one or more bootable images.
Including bootable images allows users to easily try out the BSP
on their own hardware.</p><p>In some cases, it might not be convenient to include a
bootable image.
In this case, you might want to make two versions of the
BSP available: one that contains binary images, and one
that does not.
The version that does not contain bootable images avoids
unnecessary download times for users not interested in the images.
</p><p>If you need to distribute a BSP and include bootable images or build kernel and
filesystems meant to allow users to boot the BSP for evaluation
purposes, you should put the images and artifacts within a
<code class="filename">binary/</code> subdirectory located in the
<code class="filename">meta-&lt;bsp_name&gt;</code> directory.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>If you do include a bootable image as part of the BSP and the image
was built by software covered by the GPL or other open source licenses,
it is your responsibility to understand
and meet all licensing requirements, which could include distribution
of source files.</div></li><li class="listitem"><p><span class="emphasis"><em>Use a Yocto Linux Kernel:</em></span>
Kernel recipes in the BSP should be based on a Yocto Linux kernel.
Basing your recipes on these kernels reduces the costs for maintaining
the BSP and increases its scalability.
See the <code class="filename">Yocto Linux Kernel</code> category in the
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi" target="_top"><code class="filename">Yocto Source Repositories</code></a>
for these kernels.</p></li></ul></div><p>
</p></div></div><div class="section" title="1.4. Customizing a Recipe for a BSP"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="customizing-a-recipe-for-a-bsp"></a>1.4. Customizing a Recipe for a BSP</h2></div></div></div><p>
If you plan on customizing a recipe for a particular BSP, you need to do the
following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Include within the BSP layer a <code class="filename">.bbappend</code>
file for the modified recipe.</p></li><li class="listitem"><p>Place the BSP-specific file in the BSP's recipe
<code class="filename">.bbappend</code> file path under a directory named
after the machine.</p></li></ul></div><p>
</p><p>
To better understand this, consider an example that customizes a recipe by adding
a BSP-specific configuration file named <code class="filename">interfaces</code> to the
<code class="filename">netbase_4.47.bb</code> recipe for machine "xyz".
Do the following:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Edit the <code class="filename">netbase_4.47.bbappend</code> file so that it
contains the following:
</p><pre class="literallayout">
FILESEXTRAPATHS_prepend := "${THISDIR}/files:"
PRINC := "${@int(PRINC) + 2}"
</pre></li><li class="listitem"><p>Create and place the new <code class="filename">interfaces</code>
configuration file in the BSP's layer here:
</p><pre class="literallayout">
meta-xyz/recipes-core/netbase/files/xyz/interfaces
</pre></li></ol></div><p>
</p></div><div class="section" title="1.5. BSP Licensing Considerations"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="bsp-licensing-considerations"></a>1.5. BSP Licensing Considerations</h2></div></div></div><p>
In some cases, a BSP contains separately licensed Intellectual Property (IP)
for a component or components.
For these cases, you are required to accept the terms of a commercial or other
type of license that requires some kind of explicit End User License Agreement (EULA).
Once the license is accepted, the OpenEmbedded build system can then build and
include the corresponding component in the final BSP image.
If the BSP is available as a pre-built image, you can download the image after
agreeing to the license or EULA.
</p><p>
You could find that some separately licensed components that are essential
for normal operation of the system might not have an unencumbered (or free)
substitute.
Without these essential components, the system would be non-functional.
Then again, you might find that other licensed components that are simply
'good-to-have' or purely elective do have an unencumbered, free replacement
component that you can use rather than agreeing to the separately licensed component.
Even for components essential to the system, you might find an unencumbered component
that is not identical but will work as a less-capable version of the
licensed version in the BSP recipe.
</p><p>
For cases where you can substitute a free component and still
maintain the system's functionality, the Yocto Project website's
<a class="ulink" href="http://www.yoctoproject.org/download/all?keys=&amp;download_type=1&amp;download_version=" target="_top">BSP
Download Page</a> makes available de-featured BSPs
that are completely free of any IP encumbrances.
For these cases, you can use the substitution directly and
without any further licensing requirements.
If present, these fully de-featured BSPs are named appropriately
different as compared to the names of the respective
encumbered BSPs.
If available, these substitutions are your
simplest and most preferred options.
Use of these substitutions of course assumes the resulting functionality meets
system requirements.
</p><p>
If however, a non-encumbered version is unavailable or
it provides unsuitable functionality or quality, you can use an encumbered
version.
</p><p>
A couple different methods exist within the OpenEmbedded build system to
satisfy the licensing requirements for an encumbered BSP.
The following list describes them in order of preference:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p><span class="emphasis"><em>Use the <code class="filename">LICENSE_FLAGS</code> variable
to define the recipes that have commercial or other types of
specially-licensed packages:</em></span>
For each of those recipes, you can
specify a matching license string in a
<code class="filename">local.conf</code> variable named
<code class="filename">LICENSE_FLAGS_WHITELIST</code>.
Specifying the matching license string signifies that you agree to the license.
Thus, the build system can build the corresponding recipe and include
the component in the image.
See the
"<a class="link" href="#enabling-commercially-licensed-recipes" target="_top">Enabling
Commercially Licensed Recipes</a>" section in the Yocto Project Reference
Manual for details on how to use these variables.</p><p>If you build as you normally would, without
specifying any recipes in the
<code class="filename">LICENSE_FLAGS_WHITELIST</code>, the build stops and
provides you with the list of recipes that you have
tried to include in the image that need entries in
the <code class="filename">LICENSE_FLAGS_WHITELIST</code>.
Once you enter the appropriate license flags into the whitelist,
restart the build to continue where it left off.
During the build, the prompt will not appear again
since you have satisfied the requirement.</p><p>Once the appropriate license flags are on the white list
in the <code class="filename">LICENSE_FLAGS_WHITELIST</code> variable, you
can build the encumbered image with no change at all
to the normal build process.</p></li><li class="listitem"><p><span class="emphasis"><em>Get a pre-built version of the BSP:</em></span>
You can get this type of BSP by visiting the Yocto Project website's
<a class="ulink" href="http://www.yoctoproject.org/download" target="_top">Download</a>
page and clicking on "BSP Downloads".
You can download BSP tarballs that contain proprietary components
after agreeing to the licensing
requirements of each of the individually encumbered
packages as part of the download process.
Obtaining the BSP this way allows you to access an encumbered
image immediately after agreeing to the
click-through license agreements presented by the
website.
Note that if you want to build the image
yourself using the recipes contained within the BSP
tarball, you will still need to create an
appropriate <code class="filename">LICENSE_FLAGS_WHITELIST</code> to match the
encumbered recipes in the BSP.</p></li></ol></div><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Pre-compiled images are bundled with
a time-limited kernel that runs for a
predetermined amount of time (10 days) before it forces
the system to reboot.
This limitation is meant to discourage direct redistribution
of the image.
You must eventually rebuild the image if you want to remove this restriction.
</div></div><div class="section" title="1.6. Using the Yocto Project's BSP Tools"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="using-the-yocto-projects-bsp-tools"></a>1.6. Using the Yocto Project's BSP Tools</h2></div></div></div><p>
The Yocto Project includes a couple of tools that enable
you to create a <a class="link" href="#bsp-layers" title="1.1. BSP Layers">BSP layer</a>
from scratch and do basic configuration and maintenance
of the kernel without ever looking at a metadata file.
These tools are <code class="filename">yocto-bsp</code> and <code class="filename">yocto-kernel</code>,
respectively.
</p><p>
The following sections describe the common location and help features as well
as details for the <code class="filename">yocto-bsp</code> and <code class="filename">yocto-kernel</code>
tools.
</p><div class="section" title="1.6.1. Common Features"><div class="titlepage"><div><div><h3 class="title"><a id="common-features"></a>1.6.1. Common Features</h3></div></div></div><p>
Designed to have a command interface somewhat like
<a class="link" href="#git" target="_top">Git</a>, each
tool is structured as a set of sub-commands under a
top-level command.
The top-level command (<code class="filename">yocto-bsp</code>
or <code class="filename">yocto-kernel</code>) itself does
nothing but invoke or provide help on the sub-commands
it supports.
</p><p>
Both tools reside in the <code class="filename">scripts/</code> subdirectory
of the <a class="link" href="#source-directory" target="_top">source directory</a>.
Consequently, to use the scripts, you must <code class="filename">source</code> the
environment just as you would when invoking a build:
</p><pre class="literallayout">
$ source oe-init-build-env [build_dir]
</pre><p>
</p><p>
The most immediately useful function is to get help on both tools.
The built-in help system makes it easy to drill down at
any time and view the syntax required for any specific command.
Simply enter the name of the command, or the command along with
<code class="filename">help</code> to display a list of the available sub-commands.
Here is an example:
</p><pre class="literallayout">
$ yocto-bsp
$ yocto-bsp help
Usage:
Create a customized Yocto BSP layer.
usage: yocto-bsp [--version] [--help] COMMAND [ARGS]
The most commonly used 'yocto-bsp' commands are:
create Create a new Yocto BSP
list List available values for options and BSP properties
See 'yocto-bsp help COMMAND' for more information on a specific command.
Options:
--version show program's version number and exit
-h, --help show this help message and exit
-D, --debug output debug information
</pre><p>
</p><p>
Similarly, entering just the name of a sub-command shows the detailed usage
for that sub-command:
</p><pre class="literallayout">
$ yocto-bsp create
Usage:
Create a new Yocto BSP
usage: yocto-bsp create &lt;bsp-name&gt; &lt;karch&gt; [-o &lt;DIRNAME&gt; | --outdir &lt;DIRNAME&gt;]
[-i &lt;JSON PROPERTY FILE&gt; | --infile &lt;JSON PROPERTY_FILE&gt;]
This command creates a Yocto BSP based on the specified parameters.
The new BSP will be a new BSP layer contained by default within
the top-level directory specified as 'meta-bsp-name'. The -o option
can be used to place the BSP layer in a directory with a different
name and location.
...
</pre><p>
</p><p>
For any sub-command, you can also use the word 'help' just before the
sub-command to get more extensive documentation:
</p><pre class="literallayout">
$ yocto-bsp help create
NAME
yocto-bsp create - Create a new Yocto BSP
SYNOPSIS
yocto-bsp create &lt;bsp-name&gt; &lt;karch&gt; [-o &lt;DIRNAME&gt; | --outdir &lt;DIRNAME&gt;]
[-i &lt;JSON PROPERTY FILE&gt; | --infile &lt;JSON PROPERTY_FILE&gt;]
DESCRIPTION
This command creates a Yocto BSP based on the specified
parameters. The new BSP will be a new Yocto BSP layer contained
by default within the top-level directory specified as
'meta-bsp-name'. The -o option can be used to place the BSP layer
in a directory with a different name and location.
The value of the 'karch' parameter determines the set of files
that will be generated for the BSP, along with the specific set of
'properties' that will be used to fill out the BSP-specific
portions of the BSP.
...
NOTE: Once created, you should add your new layer to your
bblayers.conf file in order for it to be subsequently seen and
modified by the yocto-kernel tool.
NOTE for x86- and x86_64-based BSPs: The generated BSP assumes the
presence of the of the meta-intel layer, so you should also have a
meta-intel layer present and added to your bblayers.conf as well.
</pre><p>
</p><p>
Now that you know where these two commands reside and how to access information
on them, you should find it relatively straightforward to discover the commands
necessary to create a BSP and perform basic kernel maintenance on that BSP using
the tools.
The next sections provide a concrete starting point to expand on a few points that
might not be immediately obvious or that could use further explanation.
</p></div><div class="section" title="1.6.2. Creating a new BSP Layer Using the yocto-bsp Script"><div class="titlepage"><div><div><h3 class="title"><a id="creating-a-new-bsp-layer-using-the-yocto-bsp-script"></a>1.6.2. Creating a new BSP Layer Using the yocto-bsp Script</h3></div></div></div><p>
The <code class="filename">yocto-bsp</code> script creates a new
<a class="link" href="#bsp-layers" title="1.1. BSP Layers">BSP layer</a> for any architecture supported
by the Yocto Project, as well as QEMU versions of the same.
The default mode of the script's operation is to prompt you for information needed
to generate the BSP layer.
For the current set of BSPs, the script prompts you for various important
parameters such as:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>which kernel to use</p></li><li class="listitem"><p>which branch of that kernel to use (or re-use)</p></li><li class="listitem"><p>whether or not to use X, and if so, which drivers to use</p></li><li class="listitem"><p>whether to turn on SMP</p></li><li class="listitem"><p>whether the BSP has a keyboard</p></li><li class="listitem"><p>whether the BSP has a touchscreen</p></li><li class="listitem"><p>any remaining configurable items associated with the BSP</p></li></ul></div><p>
</p><p>
You use the <code class="filename">yocto-bsp create</code> sub-command to create
a new BSP layer.
This command requires you to specify a particular architecture on which to
base the BSP.
Assuming you have sourced the environment, you can use the
<code class="filename">yocto-bsp list karch</code> sub-command to list the
architectures available for BSP creation as follows:
</p><pre class="literallayout">
$ yocto-bsp list karch
Architectures available:
arm
powerpc
i386
mips
x86_64
qemu
</pre><p>
</p><p>
The remainder of this section presents an example that uses
<code class="filename">myarm</code> as the machine name and <code class="filename">qemu</code>
as the machine architecture.
Of the available architectures, <code class="filename">qemu</code> is the only architecture
that causes the script to prompt you further for an actual architecture.
In every other way, this architecture is representative of how creating a BSP for
a 'real' machine would work.
The reason the example uses this architecture is because it is an emulated architecture
and can easily be followed without requiring actual hardware.
</p><p>
As the <code class="filename">yocto-bsp create</code> command runs, default values for
the prompts appear in brackets.
Pressing enter without supplying anything on the command line or pressing enter
and providing an invalid response causes the script to accept the default value.
</p><p>
Following is the complete example:
</p><pre class="literallayout">
$ yocto-bsp create myarm qemu
Which qemu architecture would you like to use? [default: x86]
1) common 32-bit x86
2) common 64-bit x86
3) common 32-bit ARM
4) common 32-bit PowerPC
5) common 32-bit MIPS
3
Would you like to use the default (3.2) kernel? (Y/n)
Do you need a new machine branch for this BSP (the alternative is to re-use an existing branch)? [Y/n]
Getting branches from remote repo git://git.yoctoproject.org/linux-yocto-3.2...
Please choose a machine branch to base this BSP on =&gt; [default: standard/default/common-pc]
1) base
2) standard/base
3) standard/default/arm-versatile-926ejs
4) standard/default/base
5) standard/default/beagleboard
6) standard/default/cedartrailbsp (copy).xml
7) standard/default/common-pc-64/base
8) standard/default/common-pc-64/jasperforest
9) standard/default/common-pc-64/romley
10) standard/default/common-pc-64/sugarbay
11) standard/default/common-pc/atom-pc
12) standard/default/common-pc/base
13) standard/default/crownbay
14) standard/default/emenlow
15) standard/default/fishriver
16) standard/default/fri2
17) standard/default/fsl-mpc8315e-rdb
18) standard/default/mti-malta32-be
19) standard/default/mti-malta32-le
20) standard/default/preempt-rt
21) standard/default/qemu-ppc32
22) standard/default/routerstationpro
23) standard/preempt-rt/base
24) standard/preempt-rt/qemu-ppc32
25) standard/preempt-rt/routerstationpro
26) standard/tiny
3
Do you need SMP support? (Y/n)
Does your BSP have a touchscreen? (y/N)
Does your BSP have a keyboard? (Y/n)
New qemu BSP created in meta-myarm
</pre><p>
Let's take a closer look at the example now:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>For the <code class="filename">qemu</code> architecture,
the script first prompts you for which emulated architecture to use.
In the example, we use the <code class="filename">arm</code> architecture.
</p></li><li class="listitem"><p>The script then prompts you for the kernel.
The default kernel is 3.2 and is acceptable.
So, the example accepts the default.
If you enter 'n', the script prompts you to further enter the kernel
you do want to use (e.g. 3.0, 3.2_preempt-rt, etc.).</p></li><li class="listitem"><p>Next, the script asks whether you would like to have a new
branch created especially for your BSP in the local
<a class="link" href="#local-kernel-files" target="_top">Linux Yocto Kernel</a>
Git repository .
If not, then the script re-uses an existing branch.</p><p>In this example, the default (or 'yes') is accepted.
Thus, a new branch is created for the BSP rather than using a common, shared
branch.
The new branch is the branch committed to for any patches you might later add.
The reason a new branch is the default is that typically
new BSPs do require BSP-specific patches.
The tool thus assumes that most of time a new branch is required.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>In the current implementation, creation or re-use of a branch does
not actually matter.
The reason is because the generated BSPs assume that patches and
configurations live in recipe-space, which is something that can be done
with or without a dedicated branch.
Generated BSPs, however, are different.
This difference becomes significant once the tool's 'publish' functionality
is implemented.</div></li><li class="listitem"><p>Regardless of which choice is made in the previous step,
you are now given the opportunity to select a particular machine branch on
which to base your new BSP-specific machine branch on
(or to re-use if you had elected to not create a new branch).
Because this example is generating an <code class="filename">arm</code> BSP, the example
uses <code class="filename">#3</code> at the prompt, which selects the arm-versatile branch.
</p></li><li class="listitem"><p>The remainder of the prompts are routine.
Defaults are accepted for each.</p></li><li class="listitem"><p>By default, the script creates the new BSP Layer in the
<a class="link" href="#build-directory" target="_top">build directory</a>.
</p></li></ol></div><p>
</p><p>
Once the BSP Layer is created, you must add it to your
<code class="filename">bblayers.conf</code> file.
Here is an example:
</p><pre class="literallayout">
BBLAYERS = " \
/usr/local/src/yocto/meta \
/usr/local/src/yocto/meta-yocto \
/usr/local/src/yocto/meta-myarm \
"
</pre><p>
Adding the layer to this file allows the build system to build the BSP and
the <code class="filename">yocto-kernel</code> tool to be able to find the layer and
other metadata it needs on which to operate.
</p></div><div class="section" title="1.6.3. Managing Kernel Patches and Config Items with yocto-kernel"><div class="titlepage"><div><div><h3 class="title"><a id="managing-kernel-patches-and-config-items-with-yocto-kernel"></a>1.6.3. Managing Kernel Patches and Config Items with yocto-kernel</h3></div></div></div><p>
Assuming you have created a <a class="link" href="#bsp-layers" title="1.1. BSP Layers">BSP Layer</a> using
<a class="link" href="#creating-a-new-bsp-layer-using-the-yocto-bsp-script" title="1.6.2. Creating a new BSP Layer Using the yocto-bsp Script">
<code class="filename">yocto-bsp</code></a> and you added it to your
<a class="link" href="#var-BBLAYERS" target="_top"><code class="filename">BBLAYERS</code></a>
variable in the <code class="filename">bblayers.conf</code> file, you can now use
the <code class="filename">yocto-kernel</code> script to add patches and configuration
items to the BSP's kernel.
</p><p>
The <code class="filename">yocto-kernel</code> script allows you to add, remove, and list patches
and kernel config settings to a BSP's kernel
<code class="filename">.bbappend</code> file.
All you need to do is use the appropriate sub-command.
Recall that the easiest way to see exactly what sub-commands are available
is to use the <code class="filename">yocto-kernel</code> built-in help as follows:
</p><pre class="literallayout">
$ yocto-kernel
Usage:
Modify and list Yocto BSP kernel config items and patches.
usage: yocto-kernel [--version] [--help] COMMAND [ARGS]
The most commonly used 'yocto-kernel' commands are:
config list List the modifiable set of bare kernel config options for a BSP
config add Add or modify bare kernel config options for a BSP
config rm Remove bare kernel config options from a BSP
patch list List the patches associated with a BSP
patch add Patch the Yocto kernel for a BSP
patch rm Remove patches from a BSP
See 'yocto-kernel help COMMAND' for more information on a specific command.
</pre><p>
</p><p>
The <code class="filename">yocto-kernel patch add</code> sub-command allows you to add a
patch to a BSP.
The following example adds two patches to the <code class="filename">myarm</code> BSP:
</p><pre class="literallayout">
$ yocto-kernel patch add myarm ~/test.patch
Added patches:
test.patch
$ yocto-kernel patch add myarm ~/yocto-testmod.patch
Added patches:
yocto-testmod.patch
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>Although the previous example adds patches one at a time, it is possible
to add multiple patches at the same time.</div><p>
</p><p>
You can verify patches have been added by using the
<code class="filename">yocto-kernel patch list</code> sub-command.
Here is an example:
</p><pre class="literallayout">
$ yocto-kernel patch list myarm
The current set of machine-specific patches for myarm is:
1) test.patch
2) yocto-testmod.patch
</pre><p>
</p><p>
You can also use the <code class="filename">yocto-kernel</code> script to
remove a patch using the <code class="filename">yocto-kernel patch rm</code> sub-command.
Here is an example:
</p><pre class="literallayout">
$ yocto-kernel patch rm myarm
Specify the patches to remove:
1) test.patch
2) yocto-testmod.patch
1
Removed patches:
test.patch
</pre><p>
</p><p>
Again, using the <code class="filename">yocto-kernel patch list</code> sub-command,
you can verify that the patch was in fact removed:
</p><pre class="literallayout">
$ yocto-kernel patch list myarm
The current set of machine-specific patches for myarm is:
1) yocto-testmod.patch
</pre><p>
</p><p>
In a completely similar way, you can use the <code class="filename">yocto-kernel config add</code>
sub-command to add one or more kernel config item settings to a BSP.
The following commands add a couple of config items to the
<code class="filename">myarm</code> BSP:
</p><pre class="literallayout">
$ yocto-kernel config add myarm CONFIG_MISC_DEVICES=y
Added items:
CONFIG_MISC_DEVICES=y
$ yocto-kernel config add myarm KCONFIG_YOCTO_TESTMOD=y
Added items:
CONFIG_YOCTO_TESTMOD=y
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>Although the previous example adds config items one at a time, it is possible
to add multiple config items at the same time.</div><p>
</p><p>
You can list the config items now associated with the BSP.
Doing so shows you the config items you added as well as others associated
with the BSP:
</p><pre class="literallayout">
$ yocto-kernel config list myarm
The current set of machine-specific kernel config items for myarm is:
1) CONFIG_MISC_DEVICES=y
2) CONFIG_YOCTO_TESTMOD=y
</pre><p>
</p><p>
Finally, you can remove one or more config items using the
<code class="filename">yocto-kernel config rm</code> sub-command in a manner
completely analogous to <code class="filename">yocto-kernel patch rm</code>.
</p></div></div></div>
</div>
<table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="100%"><tr><td align="left"><img src="figures/kernel-title.png" align="left" width="100%" /></td></tr></table>
<div xml:lang="en" class="book" lang="en"><div class="titlepage"><div><div><h1 class="title"><a id="kernel-manual"></a></h1></div><div><div class="authorgroup">
<div class="author"><h3 class="author"><span class="firstname">Bruce</span> <span class="surname">Ashfield</span></h3><div class="affiliation">
<span class="orgname">Wind River Corporation<br /></span>
</div><code class="email">&lt;<a class="email" href="mailto:bruce.ashfield@windriver.com">bruce.ashfield@windriver.com</a>&gt;</code></div>
</div></div><div><p class="copyright">Copyright © 2010-2012 Linux Foundation</p></div><div><div class="legalnotice" title="Legal Notice"><a id="id1504523"></a>
<p>
Permission is granted to copy, distribute and/or modify this document under
the terms of the <a class="ulink" href="http://creativecommons.org/licenses/by-sa/2.0/uk/" target="_top">Creative Commons Attribution-Share Alike 2.0 UK: England &amp; Wales</a> as published by Creative Commons.
</p>
<div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Due to production processes, there could be differences between the Yocto Project
documentation bundled in the release tarball and the
Yocto Project Kernel Architecture and Use Manual on
the <a class="ulink" href="http://www.yoctoproject.org" target="_top">Yocto Project</a> website.
For the latest version of this manual, see the manual on the website.
</div>
</div></div><div><div class="revhistory"><table border="1" width="100%" summary="Revision history"><tr><th align="left" valign="top" colspan="2"><b>Revision History</b></th></tr>
<tr><td align="left">Revision 0.9</td><td align="left">24 November 2010</td></tr><tr><td align="left" colspan="2">The initial document draft released with the Yocto Project 0.9 Release.</td></tr>
<tr><td align="left">Revision 1.0</td><td align="left">6 April 2011</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.0 Release.</td></tr>
<tr><td align="left">Revision 1.0.1</td><td align="left">23 May 2011</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.0.1 Release.</td></tr>
<tr><td align="left">Revision 1.1</td><td align="left">6 October 2011</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.1 Release.</td></tr>
<tr><td align="left">Revision 1.2</td><td align="left">April 2012</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.2 Release.</td></tr>
<tr><td align="left">Revision 1.3</td><td align="left">Sometime in 2012</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.3 Release.</td></tr>
</table></div></div></div><hr /></div>
<div class="chapter" title="Chapter 1. Yocto Project Kernel Architecture and Use Manual"><div class="titlepage"><div><div><h2 class="title"><a id="kernel-doc-intro"></a>Chapter 1. Yocto Project Kernel Architecture and Use Manual</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#kernel-intro-section">1.1. Introduction</a></span></dt></dl></div><div class="section" title="1.1. Introduction"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="kernel-intro-section"></a>1.1. Introduction</h2></div></div></div><p>
The Yocto Project presents kernels as a fully patched, history-clean Git
repositories.
Each repository represents selected features, board support,
and configurations extensively tested by the Yocto Project.
Yocto Project kernels allow the end user to leverage community
best practices to seamlessly manage the development, build and debug cycles.
</p><p>
This manual describes Yocto Project kernels by providing information
on history, organization, benefits, and use.
The manual consists of two sections:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Concepts:</em></span> Describes concepts behind a kernel.
You will understand how a kernel is organized and why it is organized in
the way it is. You will understand the benefits of a kernel's organization
and the mechanisms used to work with the kernel and how to apply it in your
design process.</p></li><li class="listitem"><p><span class="emphasis"><em>Using a Kernel:</em></span> Describes best practices
and "how-to" information
that lets you put a kernel to practical use.
Some examples are how to examine changes in a branch and how to
save kernel modifications.</p></li></ul></div><p>
</p><p>
For more information on the Linux kernel, see the following links:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>The Linux Foundation's guide for kernel development
process - <a class="ulink" href="http://ldn.linuxfoundation.org/book/1-a-guide-kernel-development-process" target="_top">http://ldn.linuxfoundation.org/book/1-a-guide-kernel-development-process</a></p></li><li class="listitem"><p>A fairly encompassing guide on Linux kernel development -
<a class="ulink" href="http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob_plain;f=Documentation/HOWTO;hb=HEAD" target="_top">http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob_plain;f=Documentation/HOWTO;hb=HEAD</a></p></li></ul></div><p>
</p><p>
For more discussion on the Yocto Project kernel, you can see these sections
in the Yocto Project Development Manual:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
"<a class="link" href="#kernel-overview" target="_top">Kernel Overview</a>"</p></li><li class="listitem"><p>
"<a class="link" href="#kernel-modification-workflow" target="_top">Kernel Modification Workflow</a>"
</p></li><li class="listitem"><p>
"<a class="link" href="#dev-manual-kernel-appendix" target="_top">Kernel Modification Example</a>"</p></li></ul></div><p>
</p><p>
For general information on the Yocto Project, visit the website at
<a class="ulink" href="http://www.yoctoproject.org" target="_top">http://www.yoctoproject.org</a>.
</p></div></div>
<div class="chapter" title="Chapter 2. Yocto Project Kernel Concepts"><div class="titlepage"><div><div><h2 class="title"><a id="kernel-concepts"></a>Chapter 2. Yocto Project Kernel Concepts</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#concepts-org">2.1. Introduction</a></span></dt><dt><span class="section"><a href="#kernel-goals">2.2. Kernel Goals</a></span></dt><dt><span class="section"><a href="#kernel-big-picture">2.3. Yocto Project Kernel Development and Maintenance Overview</a></span></dt><dt><span class="section"><a href="#kernel-architecture">2.4. Kernel Architecture</a></span></dt><dd><dl><dt><span class="section"><a href="#architecture-overview">2.4.1. Overview</a></span></dt><dt><span class="section"><a href="#branching-and-workflow">2.4.2. Branching Strategy and Workflow</a></span></dt><dt><span class="section"><a href="#source-code-manager-git">2.4.3. Source Code Manager - Git</a></span></dt></dl></dd><dt><span class="section"><a href="#kernel-configuration">2.5. Kernel Configuration</a></span></dt><dt><span class="section"><a href="#kernel-tools">2.6. Kernel Tools</a></span></dt></dl></div><div class="section" title="2.1. Introduction"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="concepts-org"></a>2.1. Introduction</h2></div></div></div><p>
This chapter provides conceptual information about the kernel:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Kernel Goals</p></li><li class="listitem"><p>Kernel Development and Maintenance Overview</p></li><li class="listitem"><p>Kernel Architecture</p></li><li class="listitem"><p>Kernel Tools</p></li></ul></div><p>
</p></div><div class="section" title="2.2. Kernel Goals"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="kernel-goals"></a>2.2. Kernel Goals</h2></div></div></div><p>
The complexity of embedded kernel design has increased dramatically.
Whether it is managing multiple implementations of a particular feature or tuning and
optimizing board specific features, both flexibility and maintainability are key concerns.
The Linux kernels available through the Yocto Project are presented with the embedded
developer's needs in mind and have evolved to assist in these key concerns.
For example, prior methods such as applying hundreds of patches to an extracted
tarball have been replaced with proven techniques that allow easy inspection,
bisection and analysis of changes.
Application of these techniques also creates a platform for performing integration and
collaboration with the thousands of upstream development projects.
</p><p>
With all these considerations in mind, the Yocto Project's kernel and development team
strives to attain these goals:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Allow the end user to leverage community best practices to seamlessly
manage the development, build and debug cycles.</p></li><li class="listitem"><p>Create a platform for performing integration and collaboration with the
thousands of upstream development projects that exist.</p></li><li class="listitem"><p>Provide mechanisms that support many different work flows, front-ends and
management techniques.</p></li><li class="listitem"><p>Deliver the most up-to-date kernel possible while still ensuring that
the baseline kernel is the most stable official release.</p></li><li class="listitem"><p>Include major technological features as part of the Yocto Project's
upward revision strategy.</p></li><li class="listitem"><p>Present a kernel Git repository that, similar to the upstream
<code class="filename">kernel.org</code> tree,
has a clear and continuous history.</p></li><li class="listitem"><p>Deliver a key set of supported kernel types, where each type is tailored
to meet a specific use (e.g. networking, consumer, devices, and so forth).</p></li><li class="listitem"><p>Employ a Git branching strategy that, from a developer's point of view,
results in a linear path from the baseline <code class="filename">kernel.org</code>,
through a select group of features and
ends with their BSP-specific commits.</p></li></ul></div><p>
</p></div><div class="section" title="2.3. Yocto Project Kernel Development and Maintenance Overview"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="kernel-big-picture"></a>2.3. Yocto Project Kernel Development and Maintenance Overview</h2></div></div></div><p>
Kernels available through the Yocto Project, like other kernels, are based off the Linux
kernel releases from <a class="ulink" href="http://www.kernel.org" target="_top">http://www.kernel.org</a>.
At the beginning of a major development cycle, the Yocto Project team
chooses its kernel based on factors such as release timing, the anticipated release
timing of final upstream <code class="filename">kernel.org</code> versions, and Yocto Project
feature requirements.
Typically, the kernel chosen is in the
final stages of development by the community.
In other words, the kernel is in the release
candidate or "rc" phase and not yet a final release.
But, by being in the final stages of external development, the team knows that the
<code class="filename">kernel.org</code> final release will clearly be within the early stages of
the Yocto Project development window.
</p><p>
This balance allows the team to deliver the most up-to-date kernel
as possible, while still ensuring that the team has a stable official release for
the baseline Linux kernel version.
</p><p>
The ultimate source for kernels available through the Yocto Project are released kernels
from <code class="filename">kernel.org</code>.
In addition to a foundational kernel from <code class="filename">kernel.org</code>, the
kernels available contain a mix of important new mainline
developments, non-mainline developments (when there is no alternative),
Board Support Package (BSP) developments,
and custom features.
These additions result in a commercially released Yocto Project Linux kernel that caters
to specific embedded designer needs for targeted hardware.
</p><p>
Once a kernel is officially released, the Yocto Project team goes into
their next development cycle, or upward revision (uprev) cycle, while still
continuing maintenance on the released kernel.
It is important to note that the most sustainable and stable way
to include feature development upstream is through a kernel uprev process.
Back-porting hundreds of individual fixes and minor features from various
kernel versions is not sustainable and can easily compromise quality.
</p><p>
During the uprev cycle, the Yocto Project team uses an ongoing analysis of
kernel development, BSP support, and release timing to select the best
possible <code class="filename">kernel.org</code> version.
The team continually monitors community kernel
development to look for significant features of interest.
The team does consider back-porting large features if they have a significant advantage.
User or community demand can also trigger a back-port or creation of new
functionality in the Yocto Project baseline kernel during the uprev cycle.
</p><p>
Generally speaking, every new kernel both adds features and introduces new bugs.
These consequences are the basic properties of upstream kernel development and are
managed by the Yocto Project team's kernel strategy.
It is the Yocto Project team's policy to not back-port minor features to the released kernel.
They only consider back-porting significant technological jumps - and, that is done
after a complete gap analysis.
The reason for this policy is that back-porting any small to medium sized change
from an evolving kernel can easily create mismatches, incompatibilities and very
subtle errors.
</p><p>
These policies result in both a stable and a cutting
edge kernel that mixes forward ports of existing features and significant and critical
new functionality.
Forward porting functionality in the kernels available through the Yocto Project kernel
can be thought of as a "micro uprev."
The many “micro uprevs” produce a kernel version with a mix of
important new mainline, non-mainline, BSP developments and feature integrations.
This kernel gives insight into new features and allows focused
amounts of testing to be done on the kernel, which prevents
surprises when selecting the next major uprev.
The quality of these cutting edge kernels is evolving and the kernels are used in leading edge
feature and BSP development.
</p></div><div class="section" title="2.4. Kernel Architecture"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="kernel-architecture"></a>2.4. Kernel Architecture</h2></div></div></div><p>
This section describes the architecture of the kernels available through the
Yocto Project and provides information
on the mechanisms used to achieve that architecture.
</p><div class="section" title="2.4.1. Overview"><div class="titlepage"><div><div><h3 class="title"><a id="architecture-overview"></a>2.4.1. Overview</h3></div></div></div><p>
As mentioned earlier, a key goal of the Yocto Project is to present the
developer with
a kernel that has a clear and continuous history that is visible to the user.
The architecture and mechanisms used achieve that goal in a manner similar to the
upstream <code class="filename">kernel.org</code>.
</p><p>
You can think of a Yocto Project kernel as consisting of a baseline Linux kernel with
added features logically structured on top of the baseline.
The features are tagged and organized by way of a branching strategy implemented by the
source code manager (SCM) Git.
For information on Git as applied to the Yocto Project, see the
"<a class="link" href="#git" target="_top">Git</a>" section in the
Yocto Project Development Manual.
</p><p>
The result is that the user has the ability to see the added features and
the commits that make up those features.
In addition to being able to see added features, the user can also view the history of what
made up the baseline kernel.
</p><p>
The following illustration shows the conceptual Yocto Project kernel.
</p><p>
</p><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="540"><tr style="height: 630px"><td align="center"><img src="figures/kernel-architecture-overview.png" align="middle" /></td></tr></table><p>
</p><p>
In the illustration, the "Kernel.org Branch Point"
marks the specific spot (or release) from
which the Yocto Project kernel is created.
From this point "up" in the tree, features and differences are organized and tagged.
</p><p>
The "Yocto Project Baseline Kernel" contains functionality that is common to every kernel
type and BSP that is organized further up the tree.
Placing these common features in the
tree this way means features don't have to be duplicated along individual branches of the
structure.
</p><p>
From the Yocto Project Baseline Kernel, branch points represent specific functionality
for individual BSPs as well as real-time kernels.
The illustration represents this through three BSP-specific branches and a real-time
kernel branch.
Each branch represents some unique functionality for the BSP or a real-time kernel.
</p><p>
In this example structure, the real-time kernel branch has common features for all
real-time kernels and contains
more branches for individual BSP-specific real-time kernels.
The illustration shows three branches as an example.
Each branch points the way to specific, unique features for a respective real-time
kernel as they apply to a given BSP.
</p><p>
The resulting tree structure presents a clear path of markers (or branches) to the
developer that, for all practical purposes, is the kernel needed for any given set
of requirements.
</p></div><div class="section" title="2.4.2. Branching Strategy and Workflow"><div class="titlepage"><div><div><h3 class="title"><a id="branching-and-workflow"></a>2.4.2. Branching Strategy and Workflow</h3></div></div></div><p>
The Yocto Project team creates kernel branches at points where functionality is
no longer shared and thus, needs to be isolated.
For example, board-specific incompatibilities would require different functionality
and would require a branch to separate the features.
Likewise, for specific kernel features, the same branching strategy is used.
</p><p>
This branching strategy results in a tree that has features organized to be specific
for particular functionality, single kernel types, or a subset of kernel types.
This strategy also results in not having to store the same feature twice
internally in the tree.
Rather, the kernel team stores the unique differences required to apply the
feature onto the kernel type in question.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
The Yocto Project team strives to place features in the tree such that they can be
shared by all boards and kernel types where possible.
However, during development cycles or when large features are merged,
the team cannot always follow this practice.
In those cases, the team uses isolated branches to merge features.
</div><p>
</p><p>
BSP-specific code additions are handled in a similar manner to kernel-specific additions.
Some BSPs only make sense given certain kernel types.
So, for these types, the team creates branches off the end of that kernel type for all
of the BSPs that are supported on that kernel type.
From the perspective of the tools that create the BSP branch, the BSP is really no
different than a feature.
Consequently, the same branching strategy applies to BSPs as it does to features.
So again, rather than store the BSP twice, the team only stores the unique
differences for the BSP across the supported multiple kernels.
</p><p>
While this strategy can result in a tree with a significant number of branches, it is
important to realize that from the developer's point of view, there is a linear
path that travels from the baseline <code class="filename">kernel.org</code>, through a select
group of features and ends with their BSP-specific commits.
In other words, the divisions of the kernel are transparent and are not relevant
to the developer on a day-to-day basis.
From the developer's perspective, this path is the "master" branch.
The developer does not need to be aware of the existence of any other branches at all.
Of course, there is value in the existence of these branches
in the tree, should a person decide to explore them.
For example, a comparison between two BSPs at either the commit level or at the line-by-line
code <code class="filename">diff</code> level is now a trivial operation.
</p><p>
Working with the kernel as a structured tree follows recognized community best practices.
In particular, the kernel as shipped with the product, should be
considered an "upstream source" and viewed as a series of
historical and documented modifications (commits).
These modifications represent the development and stabilization done
by the Yocto Project kernel development team.
</p><p>
Because commits only change at significant release points in the product life cycle,
developers can work on a branch created
from the last relevant commit in the shipped Yocto Project kernel.
As mentioned previously, the structure is transparent to the developer
because the kernel tree is left in this state after cloning and building the kernel.
</p></div><div class="section" title="2.4.3. Source Code Manager - Git"><div class="titlepage"><div><div><h3 class="title"><a id="source-code-manager-git"></a>2.4.3. Source Code Manager - Git</h3></div></div></div><p>
The Source Code Manager (SCM) is Git.
This SCM is the obvious mechanism for meeting the previously mentioned goals.
Not only is it the SCM for <code class="filename">kernel.org</code> but,
Git continues to grow in popularity and supports many different work flows,
front-ends and management techniques.
</p><p>
You can find documentation on Git at <a class="ulink" href="http://git-scm.com/documentation" target="_top">http://git-scm.com/documentation</a>.
You can also get an introduction to Git as it applies to the Yocto Project in the
"<a class="link" href="#git" target="_top">Git</a>"
section in the Yocto Project Development Manual.
These referenced sections overview Git and describe a minimal set of
commands that allows you to be functional using Git.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
You can use as much, or as little, of what Git has to offer to accomplish what
you need for your project.
You do not have to be a "Git Master" in order to use it with the Yocto Project.
</div><p>
</p></div></div><div class="section" title="2.5. Kernel Configuration"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="kernel-configuration"></a>2.5. Kernel Configuration</h2></div></div></div><p>
Kernel configuration, along with kernel features, defines how a kernel
image is built for the Yocto Project.
Through configuration settings, you can customize a Yocto Project kernel to be
specific to particular hardware.
For example, you can specify sound support or networking support.
This section describes basic concepts behind Kernel configuration within the
Yocto Project and references you to other areas for specific configuration
applications.
</p><p>
Conceptually, configuration of a Yocto Project kernel occurs similarly to that needed for any
Linux kernel.
The build process for a Yocto Project kernel uses a <code class="filename">.config</code> file, which
is created through the Linux Kernel Coinfiguration (LKC) tool.
You can directly set various configurations in the
<code class="filename">.config</code> file by using the <code class="filename">menuconfig</code>
tool as built by BitBake.
You can also define configurations in the file by using configuration fragments.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
It is not recommended that you edit the <code class="filename">.config</code> file directly.
</div><p>
Here are some brief descriptions of the ways you can affect the
<code class="filename">.config</code> file:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>The <code class="filename">menuconfig</code> Tool:</em></span>
One of many front-ends that allows you to define kernel configurations.
Some others are <code class="filename">make config</code>,
<code class="filename">make nconfig</code>, and <code class="filename">make gconfig</code>.
In the Yocto Project environment, you must use BitBake to build the
<code class="filename">menuconfig</code> tool before you can use it to define
configurations:
</p><pre class="literallayout">
$ bitbake linux-yocto -c menuconfig
</pre><p>
After the tool is built, you can interact with it normally.
You can see how <code class="filename">menuconfig</code> is used to change a simple
kernel configuration in the
"<a class="link" href="#changing-the-config-smp-configuration-using-menuconfig" target="_top">Changing the  <code class="filename">CONFIG_SMP</code> Configuration Using  <code class="filename">menuconfig</code></a>"
section of the Yocto Project Development Manual.
For general information on <code class="filename">menuconfig</code>, see
<a class="ulink" href="http://en.wikipedia.org/wiki/Menuconfig" target="_top">http://en.wikipedia.org/wiki/Menuconfig</a>.
</p></li><li class="listitem"><p><span class="emphasis"><em>Configuration Fragments:</em></span> A file with a
list of kernel options just as they would appear syntactically in the
<code class="filename">.config</code> file.
Configuration fragments are typically logical groupings and are assembled
by the OpenEmbedded build system to produce input used by the LKC
that ultimately generates the <code class="filename">.config</code> file.</p><p>The
<code class="filename"><a class="link" href="#var-KERNEL_FEATURES" target="_top">KERNEL_FEATURES</a></code>
variable can be used to list configuration fragments.
For further discussion on applying configuration fragments, see the
"<a class="link" href="#bsp-filelayout-kernel" target="_top">Linux Kernel Configuration</a>"
section in the Yocto Project Board Support Package (BSP) Guide.
</p></li></ul></div><p>
</p></div><div class="section" title="2.6. Kernel Tools"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="kernel-tools"></a>2.6. Kernel Tools</h2></div></div></div><p>
Since most standard workflows involve moving forward with an existing tree by
continuing to add and alter the underlying baseline, the tools that manage
the Yocto Project's kernel construction are largely hidden from the developer to
present a simplified view of the kernel for ease of use.
</p><p>
Fundamentally, the kernel tools that manage and construct the
Yocto Project kernel accomplish the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Group patches into named, reusable features.</p></li><li class="listitem"><p>Allow top-down control of included features.</p></li><li class="listitem"><p>Bind kernel configurations to kernel patches and features.</p></li><li class="listitem"><p>Present a seamless Git repository that blends Yocto Project value
with the <code class="filename">kernel.org</code> history and development.</p></li></ul></div><p>
</p></div></div>
<div class="chapter" title="Chapter 3. Working with the Yocto Project Kernel"><div class="titlepage"><div><div><h2 class="title"><a id="kernel-how-to"></a>Chapter 3. Working with the Yocto Project Kernel</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#actions-org">3.1. Introduction</a></span></dt><dt><span class="section"><a href="#tree-construction">3.2. Tree Construction</a></span></dt><dt><span class="section"><a href="#build-strategy">3.3. Build Strategy</a></span></dt><dt><span class="section"><a href="#workflow-examples">3.4. Workflow Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#change-inspection-kernel-changes-commits">3.4.1. Change Inspection: Changes/Commits</a></span></dt><dt><span class="section"><a href="#development-saving-kernel-modifications">3.4.2. Development: Saving Kernel Modifications</a></span></dt><dt><span class="section"><a href="#scm-working-with-the-yocto-project-kernel-in-another-scm">3.4.3. Working with the Yocto Project Kernel in Another SCM</a></span></dt><dt><span class="section"><a href="#bsp-creating">3.4.4. Creating a BSP Based on an Existing Similar BSP</a></span></dt><dt><span class="section"><a href="#tip-dirty-string">3.4.5. "-dirty" String</a></span></dt></dl></dd></dl></div><div class="section" title="3.1. Introduction"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="actions-org"></a>3.1. Introduction</h2></div></div></div><p>
This chapter describes how to accomplish tasks involving a kernel's tree structure.
The information is designed to help the developer that wants to modify the Yocto
Project kernel and contribute changes upstream to the Yocto Project.
The information covers the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Tree construction</p></li><li class="listitem"><p>Build strategies</p></li><li class="listitem"><p>Workflow examples</p></li></ul></div><p>
</p></div><div class="section" title="3.2. Tree Construction"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="tree-construction"></a>3.2. Tree Construction</h2></div></div></div><p>
This section describes construction of the Yocto Project kernel source repositories
as accomplished by the Yocto Project team to create kernel repositories.
These kernel repositories are found under the heading "Yocto Linux Kernel" at
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi" target="_top">http://git.yoctoproject.org/cgit.cgi</a>
and can be shipped as part of a Yocto Project release.
The team creates these repositories by
compiling and executing the set of feature descriptions for every BSP/feature
in the product.
Those feature descriptions list all necessary patches,
configuration, branching, tagging and feature divisions found in a kernel.
Thus, the Yocto Project kernel repository (or tree) is built.
</p><p>
The existence of this tree allows you to access and clone a particular
Yocto Project kernel repository and use it to build images based on their configurations
and features.
</p><p>
You can find the files used to describe all the valid features and BSPs
in the Yocto Project kernel in any clone of the Yocto Project kernel source repository
Git tree.
For example, the following command clones the Yocto Project baseline kernel that
branched off of <code class="filename">linux.org</code> version 3.4:
</p><pre class="literallayout">
$ git clone git://git.yoctoproject.org/linux-yocto-3.4
</pre><p>
For another example of how to set up a local Git repository of the Yocto Project
kernel files, see the
"<a class="link" href="#local-kernel-files" target="_top">Yocto Project Kernel</a>" bulleted
item in the Yocto Project Development Manual.
</p><p>
Once you have cloned the kernel Git repository on your local machine, you can
switch to the <code class="filename">meta</code> branch within the repository.
Here is an example that assumes the local Git repository for the kernel is in
a top-level directory named <code class="filename">linux-yocto-3.4</code>:
</p><pre class="literallayout">
$ cd ~/linux-yocto-3.4
$ git checkout -b meta origin/meta
</pre><p>
Once you have checked out and switched to the <code class="filename">meta</code> branch,
you can see a snapshot of all the kernel configuration and feature descriptions that are
used to build that particular kernel repository.
These descriptions are in the form of <code class="filename">.scc</code> files.
</p><p>
You should realize, however, that browsing your local kernel repository
for feature descriptions and patches is not an effective way to determine what is in a
particular kernel branch.
Instead, you should use Git directly to discover the changes in a branch.
Using Git is an efficient and flexible way to inspect changes to the kernel.
For examples showing how to use Git to inspect kernel commits, see the following sections
in this chapter.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Ground up reconstruction of the complete kernel tree is an action only taken by the
Yocto Project team during an active development cycle.
When you create a clone of the kernel Git repository, you are simply making it
efficiently available for building and development.
</div><p>
</p><p>
The following steps describe what happens when the Yocto Project Team constructs
the Yocto Project kernel source Git repository (or tree) found at
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi" target="_top">http://git.yoctoproject.org/cgit.cgi</a> given the
introduction of a new top-level kernel feature or BSP.
These are the actions that effectively create the tree
that includes the new feature, patch or BSP:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>A top-level kernel feature is passed to the kernel build subsystem.
Normally, this feature is a BSP for a particular kernel type.</p></li><li class="listitem"><p>The file that describes the top-level feature is located by searching
these system directories:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>The in-tree kernel-cache directories, which are located
in <code class="filename">meta/cfg/kernel-cache</code></p></li><li class="listitem"><p>Areas pointed to by <code class="filename">SRC_URI</code> statements
found in recipes</p></li></ul></div><p>
For a typical build, the target of the search is a
feature description in an <code class="filename">.scc</code> file
whose name follows this format:
</p><pre class="literallayout">
&lt;bsp_name&gt;-&lt;kernel_type&gt;.scc
</pre><p>
</p></li><li class="listitem"><p>Once located, the feature description is either compiled into a simple script
of actions, or into an existing equivalent script that is already part of the
shipped kernel.</p></li><li class="listitem"><p>Extra features are appended to the top-level feature description.
These features can come from the
<a class="link" href="#var-KERNEL_FEATURES" target="_top"><code class="filename">KERNEL_FEATURES</code></a>
variable in recipes.</p></li><li class="listitem"><p>Each extra feature is located, compiled and appended to the script
as described in step three.</p></li><li class="listitem"><p>The script is executed to produce a series of <code class="filename">meta-*</code>
directories.
These directories are descriptions of all the branches, tags, patches and configurations that
need to be applied to the base Git repository to completely create the
source (build) branch for the new BSP or feature.</p></li><li class="listitem"><p>The base repository is cloned, and the actions
listed in the <code class="filename">meta-*</code> directories are applied to the
tree.</p></li><li class="listitem"><p>The Git repository is left with the desired branch checked out and any
required branching, patching and tagging has been performed.</p></li></ol></div><p>
</p><p>
The kernel tree is now ready for developer consumption to be locally cloned,
configured, and built into a Yocto Project kernel specific to some target hardware.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>The generated <code class="filename">meta-*</code> directories add to the kernel
as shipped with the Yocto Project release.
Any add-ons and configuration data are applied to the end of an existing branch.
The full repository generation that is found in the
official Yocto Project kernel repositories at
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi" target="_top">http://git.yoctoproject.org/cgit.cgi</a>
is the combination of all supported boards and configurations.</p><p>The technique the Yocto Project team uses is flexible and allows for seamless
blending of an immutable history with additional patches specific to a
deployment.
Any additions to the kernel become an integrated part of the branches.</p></div><p>
</p></div><div class="section" title="3.3. Build Strategy"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="build-strategy"></a>3.3. Build Strategy</h2></div></div></div><p>
Once a local Git repository of the Yocto Project kernel exists on a development system,
you can consider the compilation phase of kernel development - building a kernel image.
Some prerequisites exist that are validated by the build process before compilation
starts:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>The <code class="filename">SRC_URI</code> points to the kernel Git
repository.</p></li><li class="listitem"><p>A BSP build branch exists.
This branch has the following form:
</p><pre class="literallayout">
&lt;kernel_type&gt;/&lt;bsp_name&gt;
</pre></li></ul></div><p>
The OpenEmbedded build system makes sure these conditions exist before attempting compilation.
Other means, however, do exist, such as as bootstrapping a BSP, see
the "<a class="link" href="#workflow-examples" title="3.4. Workflow Examples">Workflow Examples</a>".
</p><p>
Before building a kernel, the build process verifies the tree
and configures the kernel by processing all of the
configuration "fragments" specified by feature descriptions in the <code class="filename">.scc</code>
files.
As the features are compiled, associated kernel configuration fragments are noted
and recorded in the <code class="filename">meta-*</code> series of directories in their compilation order.
The fragments are migrated, pre-processed and passed to the Linux Kernel
Configuration subsystem (<code class="filename">lkc</code>) as raw input in the form
of a <code class="filename">.config</code> file.
The <code class="filename">lkc</code> uses its own internal dependency constraints to do the final
processing of that information and generates the final <code class="filename">.config</code> file
that is used during compilation.
</p><p>
Using the board's architecture and other relevant values from the board's template,
kernel compilation is started and a kernel image is produced.
</p><p>
The other thing that you notice once you configure a kernel is that
the build process generates a build tree that is separate from your kernel's local Git
source repository tree.
This build tree has a name that uses the following form, where
<code class="filename">${MACHINE}</code> is the metadata name of the machine (BSP) and "kernel_type" is one
of the Yocto Project supported kernel types (e.g. "standard"):
</p><pre class="literallayout">
linux-${MACHINE}-&lt;kernel_type&gt;-build
</pre><p>
</p><p>
The existing support in the <code class="filename">kernel.org</code> tree achieves this
default functionality.
</p><p>
This behavior means that all the generated files for a particular machine or BSP are now in
the build tree directory.
The files include the final <code class="filename">.config</code> file, all the <code class="filename">.o</code>
files, the <code class="filename">.a</code> files, and so forth.
Since each machine or BSP has its own separate build directory in its own separate branch
of the Git repository, you can easily switch between different builds.
</p></div><div class="section" title="3.4. Workflow Examples"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="workflow-examples"></a>3.4. Workflow Examples</h2></div></div></div><p>
As previously noted, the Yocto Project kernel has built-in Git integration.
However, these utilities are not the only way to work with the kernel repository.
The Yocto Project has not made changes to Git or to other tools that
would invalidate alternate workflows.
Additionally, the way the kernel repository is constructed results in using
only core Git functionality, thus allowing any number of tools or front ends to use the
resulting tree.
</p><p>
This section contains several workflow examples.
Many of the examples use Git commands.
You can find Git documentation at
<a class="ulink" href="http://git-scm.com/documentation" target="_top">http://git-scm.com/documentation</a>.
You can find a simple overview of using Git with the Yocto Project in the
"<a class="link" href="#git" target="_top">Git</a>"
section of the Yocto Project Development Manual.
</p><div class="section" title="3.4.1. Change Inspection: Changes/Commits"><div class="titlepage"><div><div><h3 class="title"><a id="change-inspection-kernel-changes-commits"></a>3.4.1. Change Inspection: Changes/Commits</h3></div></div></div><p>
A common question when working with a kernel is:
"What changes have been applied to this tree?"
</p><p>
In projects that have a collection of directories that
contain patches to the kernel, it is possible to inspect or "grep" the contents
of the directories to get a general feel for the changes.
This sort of patch inspection is not an efficient way to determine what has been
done to the kernel.
The reason it is inefficient is because there are many optional patches that are
selected based on the kernel type and the feature description.
Additionally, patches could exist in directories that are not included in the search.
</p><p>
A more efficient way to determine what has changed in the branch is to use
Git and inspect or search the kernel tree.
This method gives you a full view of not only the source code modifications,
but also provides the reasons for the changes.
</p><div class="section" title="3.4.1.1. What Changed in a Kernel?"><div class="titlepage"><div><div><h4 class="title"><a id="what-changed-in-a-kernel"></a>3.4.1.1. What Changed in a Kernel?</h4></div></div></div><p>
Following are a few examples that show how to use Git commands to examine changes.
Because Git repositories in the Yocto Project do not break existing Git
functionality, and because there exists many permutations of these types of
Git commands, many methods exist by which you can discover changes.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
In the following examples, unless you provide a commit range,
<code class="filename">kernel.org</code> history is blended with Yocto Project
kernel changes.
You can form ranges by using branch names from the kernel tree as the
upper and lower commit markers with the Git commands.
You can see the branch names through the web interface to the
Yocto Project source repositories at
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi" target="_top">http://git.yoctoproject.org/cgit.cgi</a>.
For example, the branch names for the <code class="filename">linux-yocto-3.4</code>
kernel repository can be seen at
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi/linux-yocto-3.4/refs/heads" target="_top">http://git.yoctoproject.org/cgit.cgi/linux-yocto-3.4/refs/heads</a>.
</div><p>
To see a full range of the changes, use the
<code class="filename">git whatchanged</code> command and specify a commit range
for the branch (<code class="filename">&lt;commit&gt;..&lt;commit&gt;</code>).
</p><p>
Here is an example that looks at what has changed in the
<code class="filename">emenlow</code> branch of the
<code class="filename">linux-yocto-3.4</code> kernel.
The lower commit range is the commit associated with the
<code class="filename">standard/base</code> branch, while
the upper commit range is the commit associated with the
<code class="filename">standard/emenlow</code> branch.
</p><pre class="literallayout">
$ git whatchanged origin/standard/base..origin/standard/emenlow
</pre><p>
</p><p>
To see a summary of changes use the <code class="filename">git log</code> command.
Here is an example using the same branches:
</p><pre class="literallayout">
$ git log --oneline origin/standard/base..origin/standard/emenlow
</pre><p>
The <code class="filename">git log</code> output might be more useful than
the <code class="filename">git whatchanged</code> as you get
a short, one-line summary of each change and not the entire commit.
</p><p>
If you want to see code differences associated with all the changes, use
the <code class="filename">git diff</code> command.
Here is an example:
</p><pre class="literallayout">
$ git diff origin/standard/base..origin/standard/emenlow
</pre><p>
</p><p>
You can see the commit log messages and the text differences using the
<code class="filename">git show</code> command:
Here is an example:
</p><pre class="literallayout">
$ git show origin/standard/base..origin/standard/emenlow
</pre><p>
</p><p>
You can create individual patches for each change by using the
<code class="filename">git format-patch</code> command.
Here is an example that that creates patch files for each commit and
places them in your <code class="filename">Documents</code> directory:
</p><pre class="literallayout">
$ git format-patch -o $HOME/Documents origin/standard/base..origin/standard/emenlow
</pre><p>
</p></div><div class="section" title="3.4.1.2. Show a Particular Feature or Branch Change"><div class="titlepage"><div><div><h4 class="title"><a id="show-a-particular-feature-or-branch-change"></a>3.4.1.2. Show a Particular Feature or Branch Change</h4></div></div></div><p>
Developers use tags in the Yocto Project kernel tree to divide changes for significant
features or branches.
Once you know a particular tag, you can use Git commands
to show changes associated with the tag and find the branches that contain
the feature.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Because BSP branch, <code class="filename">kernel.org</code>, and feature tags are all
present, there could be many tags.
</div><p>
The <code class="filename">git show &lt;tag&gt;</code> command shows changes that are tagged by
a feature.
Here is an example that shows changes tagged by the <code class="filename">systemtap</code>
feature:
</p><pre class="literallayout">
$ git show systemtap
</pre><p>
You can use the <code class="filename">git branch --contains &lt;tag&gt;</code> command
to show the branches that contain a particular feature.
This command shows the branches that contain the <code class="filename">systemtap</code>
feature:
</p><pre class="literallayout">
$ git branch --contains systemtap
</pre><p>
</p><p>
You can use many other comparisons to isolate BSP and kernel changes.
For example, you can compare against <code class="filename">kernel.org</code> tags
such as the <code class="filename">v3.4</code> tag.
</p></div></div><div class="section" title="3.4.2. Development: Saving Kernel Modifications"><div class="titlepage"><div><div><h3 class="title"><a id="development-saving-kernel-modifications"></a>3.4.2. Development: Saving Kernel Modifications</h3></div></div></div><p>
Another common operation is to build a BSP supplied by the Yocto Project, make some
changes, rebuild, and then test.
Those local changes often need to be exported, shared or otherwise maintained.
</p><p>
Since the Yocto Project kernel source tree is backed by Git, this activity is
much easier as compared to with previous releases.
Because Git tracks file modifications, additions and deletions, it is easy
to modify the code and later realize that you need to save the changes.
It is also easy to determine what has changed.
This method also provides many tools to commit, undo and export those modifications.
</p><p>
This section and its sub-sections, describe general application of Git's
<code class="filename">push</code> and <code class="filename">pull</code> commands, which are used to
get your changes upstream or source your code from an upstream repository.
The Yocto Project provides scripts that help you work in a collaborative development
environment.
For information on these scripts, see the
"<a class="link" href="#pushing-a-change-upstream" target="_top">Using Scripts to Push a Change
Upstream and Request a Pull</a>" and
"<a class="link" href="#submitting-a-patch" target="_top">Using Email to Submit a Patch</a>"
sections in the Yocto Project Development Manual.
</p><p>
There are many ways to save kernel modifications.
The technique employed
depends on the destination for the patches:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Bulk storage</p></li><li class="listitem"><p>Internal sharing either through patches or by using Git</p></li><li class="listitem"><p>External submissions</p></li><li class="listitem"><p>Exporting for integration into another Source Code
Manager (SCM)</p></li></ul></div><p>
</p><p>
Because of the following list of issues, the destination of the patches also influences
the method for gathering them:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Bisectability</p></li><li class="listitem"><p>Commit headers</p></li><li class="listitem"><p>Division of subsystems for separate submission or review</p></li></ul></div><p>
</p><div class="section" title="3.4.2.1. Bulk Export"><div class="titlepage"><div><div><h4 class="title"><a id="bulk-export"></a>3.4.2.1. Bulk Export</h4></div></div></div><p>
This section describes how you can "bulk" export changes that have not
been separated or divided.
This situation works well when you are simply storing patches outside of the kernel
source repository, either permanently or temporarily, and you are not committing
incremental changes during development.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
This technique is not appropriate for full integration of upstream submission
because changes are not properly divided and do not provide an avenue for per-change
commit messages.
Therefore, this example assumes that changes have not been committed incrementally
during development and that you simply must gather and export them.
</div><p>
</p><pre class="literallayout">
# bulk export of ALL modifications without separation or division
# of the changes
$ git add .
$ git commit -s -a -m &lt;msg&gt;
or
$ git commit -s -a # and interact with $EDITOR
</pre><p>
</p><p>
The previous operations capture all the local changes in the project source
tree in a single Git commit.
And, that commit is also stored in the project's source tree.
</p><p>
Once the changes are exported, you can restore them manually using a template
or through integration with the <code class="filename">default_kernel</code>.
</p></div><div class="section" title="3.4.2.2. Incremental/Planned Sharing"><div class="titlepage"><div><div><h4 class="title"><a id="incremental-planned-sharing"></a>3.4.2.2. Incremental/Planned Sharing</h4></div></div></div><p>
This section describes how to save modifications when you are making incremental
commits or practicing planned sharing.
The examples in this section assume that you have incrementally committed
changes to the tree during development and now need to export them.
The sections that follow
describe how you can export your changes internally through either patches or by
using Git commands.
</p><p>
During development, the following commands are of interest.
For full Git documentation, refer to the Git documentation at
<a class="ulink" href="http://github.com" target="_top">http://github.com</a>.
</p><pre class="literallayout">
# edit a file
$ vi &lt;path&gt;/file
# stage the change
$ git add &lt;path&gt;/file
# commit the change
$ git commit -s
# remove a file
$ git rm &lt;path&gt;/file
# commit the change
$ git commit -s
... etc.
</pre><p>
</p><p>
Distributed development with Git is possible when you use a universally
agreed-upon unique commit identifier (set by the creator of the commit) that maps to a
specific change set with a specific parent.
This identifier is created for you when
you create a commit, and is re-created when you amend, alter or re-apply
a commit.
As an individual in isolation, this is of no interest.
However, if you
intend to share your tree with normal Git <code class="filename">push</code> and
<code class="filename">pull</code> operations for
distributed development, you should consider the ramifications of changing a
commit that you have already shared with others.
</p><p>
Assuming that the changes have not been pushed upstream, or pulled into
another repository, you can update both the commit content and commit messages
associated with development by using the following commands:
</p><pre class="literallayout">
$ Git add &lt;path&gt;/file
$ Git commit --amend
$ Git rebase or Git rebase -i
</pre><p>
</p><p>
Again, assuming that the changes have not been pushed upstream, and that
no pending works-in-progress exist (use <code class="filename">git status</code> to check), then
you can revert (undo) commits by using the following commands:
</p><pre class="literallayout">
# remove the commit, update working tree and remove all
# traces of the change
$ git reset --hard HEAD^
# remove the commit, but leave the files changed and staged for re-commit
$ git reset --soft HEAD^
# remove the commit, leave file change, but not staged for commit
$ git reset --mixed HEAD^
</pre><p>
</p><p>
You can create branches, "cherry-pick" changes, or perform any number of Git
operations until the commits are in good order for pushing upstream
or for pull requests.
After a <code class="filename">push</code> or <code class="filename">pull</code> command,
commits are normally considered
"permanent" and you should not modify them.
If the commits need to be changed, you can incrementally do so with new commits.
These practices follow standard Git workflow and the <code class="filename">kernel.org</code> best
practices, which is recommended.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
It is recommended to tag or branch before adding changes to a Yocto Project
BSP or before creating a new one.
The reason for this recommendation is because the branch or tag provides a
reference point to facilitate locating and exporting local changes.
</div><p>
</p><div class="section" title="3.4.2.2.1. Exporting Changes Internally by Using Patches"><div class="titlepage"><div><div><h5 class="title"><a id="export-internally-via-patches"></a>3.4.2.2.1. Exporting Changes Internally by Using Patches</h5></div></div></div><p>
This section describes how you can extract committed changes from a working directory
by exporting them as patches.
Once the changes have been extracted, you can use the patches for upstream submission,
place them in a Yocto Project template for automatic kernel patching,
or apply them in many other common uses.
</p><p>
This example shows how to create a directory with sequentially numbered patches.
Once the directory is created, you can apply it to a repository using the
<code class="filename">git am</code> command to reproduce the original commit and all
the related information such as author, date, commit log, and so forth.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
The new commit identifiers (ID) will be generated upon re-application.
This action reflects that the commit is now applied to an underlying commit
with a different ID.
</div><p>
</p><pre class="literallayout">
# &lt;first-commit&gt; can be a tag if one was created before development
# began. It can also be the parent branch if a branch was created
# before development began.
$ git format-patch -o &lt;dir&gt; &lt;first commit&gt;..&lt;last commit&gt;
</pre><p>
</p><p>
In other words:
</p><pre class="literallayout">
# Identify commits of interest.
# If the tree was tagged before development
$ git format-patch -o &lt;save dir&gt; &lt;tag&gt;
# If no tags are available
$ git format-patch -o &lt;save dir&gt; HEAD^ # last commit
$ git format-patch -o &lt;save dir&gt; HEAD^^ # last 2 commits
$ git whatchanged # identify last commit
$ git format-patch -o &lt;save dir&gt; &lt;commit id&gt;
$ git format-patch -o &lt;save dir&gt; &lt;rev-list&gt;
</pre><p>
</p></div><div class="section" title="3.4.2.2.2. Exporting Changes Internally by Using Git"><div class="titlepage"><div><div><h5 class="title"><a id="export-internally-via-git"></a>3.4.2.2.2. Exporting Changes Internally by Using Git</h5></div></div></div><p>
This section describes how you can export changes from a working directory
by pushing the changes into a master repository or by making a pull request.
Once you have pushed the changes to the master repository, you can then
pull those same changes into a new kernel build at a later time.
</p><p>
Use this command form to push the changes:
</p><pre class="literallayout">
$ git push ssh://&lt;master_server&gt;/&lt;path_to_repo&gt;
&lt;local_branch&gt;:&lt;remote_branch&gt;
</pre><p>
</p><p>
For example, the following command pushes the changes from your local branch
<code class="filename">yocto/standard/common-pc/base</code> to the remote branch with the same name
in the master repository <code class="filename">//git.mycompany.com/pub/git/kernel-3.4</code>.
</p><pre class="literallayout">
$ git push ssh://git.mycompany.com/pub/git/kernel-3.4 \
yocto/standard/common-pc/base:yocto/standard/common-pc/base
</pre><p>
</p><p>
A pull request entails using the <code class="filename">git request-pull</code> command to compose
an email to the
maintainer requesting that a branch be pulled into the master repository, see
<a class="ulink" href="http://github.com/guides/pull-requests" target="_top">http://github.com/guides/pull-requests</a> for an example.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Other commands such as <code class="filename">git stash</code> or branching can also be used to save
changes, but are not covered in this document.
</div><p>
</p></div></div><div class="section" title="3.4.2.3. Exporting Changes for External (Upstream) Submission"><div class="titlepage"><div><div><h4 class="title"><a id="export-for-external-upstream-submission"></a>3.4.2.3. Exporting Changes for External (Upstream) Submission</h4></div></div></div><p>
This section describes how to export changes for external upstream submission.
If the patch series is large or the maintainer prefers to pull
changes, you can submit these changes by using a pull request.
However, it is common to send patches as an email series.
This method allows easy review and integration of the changes.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Before sending patches for review be sure you understand the
community standards for submitting and documenting changes and follow their best practices.
For example, kernel patches should follow standards such as:
<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
<a class="ulink" href="http://linux.yyz.us/patch-format.html" target="_top">http://linux.yyz.us/patch-format.html</a></p></li><li class="listitem"><p>Documentation/SubmittingPatches (in any linux
kernel source tree)</p></li></ul></div></div><p>
</p><p>
The messages used to commit changes are a large part of these standards.
Consequently, be sure that the headers for each commit have the required information.
For information on how to follow the Yocto Project commit message standards, see the
"<a class="link" href="#how-to-submit-a-change" target="_top">How to Submit a
Change</a>" section in the Yocto Project Development Manual.
</p><p>
If the initial commits were not properly documented or do not meet those standards,
you can re-base by using the <code class="filename">git rebase -i</code> command to
manipulate the commits and
get them into the required format.
Other techniques such as branching and cherry-picking commits are also viable options.
</p><p>
Once you complete the commits, you can generate the email that sends the patches
to the maintainer(s) or lists that review and integrate changes.
The command <code class="filename">git send-email</code> is commonly used to ensure
that patches are properly
formatted for easy application and avoid mailer-induced patch damage.
</p><p>
The following is an example of dumping patches for external submission:
</p><pre class="literallayout">
# dump the last 4 commits
$ git format-patch --thread -n -o ~/rr/ HEAD^^^^
$ git send-email --compose --subject '[RFC 0/N] &lt;patch series summary&gt;' \
--to foo@yoctoproject.org --to bar@yoctoproject.org \
--cc list@yoctoproject.org ~/rr
# the editor is invoked for the 0/N patch, and when complete the entire
# series is sent via email for review
</pre><p>
</p></div><div class="section" title="3.4.2.4. Exporting Changes for Import into Another SCM"><div class="titlepage"><div><div><h4 class="title"><a id="export-for-import-into-other-scm"></a>3.4.2.4. Exporting Changes for Import into Another SCM</h4></div></div></div><p>
When you want to export changes for import into another
Source Code Manager (SCM), you can use any of the previously discussed
techniques.
However, if the patches are manually applied to a secondary tree and then
that tree is checked into the SCM, you can lose change information such as
commit logs.
This process is not recommended.
</p><p>
Many SCMs can directly import Git commits, or can translate Git patches so that
information is not lost.
Those facilities are SCM-dependent and you should use them whenever possible.
</p></div></div><div class="section" title="3.4.3. Working with the Yocto Project Kernel in Another SCM"><div class="titlepage"><div><div><h3 class="title"><a id="scm-working-with-the-yocto-project-kernel-in-another-scm"></a>3.4.3. Working with the Yocto Project Kernel in Another SCM</h3></div></div></div><p>
This section describes kernel development in an SCM other than Git,
which is not the same as exporting changes to another SCM described earlier.
For this scenario, you use the OpenEmbedded build system to
develop the kernel in a different SCM.
The following must be true for you to accomplish this:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>The delivered Yocto Project kernel must be exported into the second
SCM.</p></li><li class="listitem"><p>Development must be exported from that secondary SCM into a
format that can be used by the OpenEmbedded build system.</p></li></ul></div><p>
</p><div class="section" title="3.4.3.1. Exporting the Delivered Kernel to the SCM"><div class="titlepage"><div><div><h4 class="title"><a id="exporting-delivered-kernel-to-scm"></a>3.4.3.1. Exporting the Delivered Kernel to the SCM</h4></div></div></div><p>
Depending on the SCM, it might be possible to export the entire Yocto Project
kernel Git repository, branches and all, into a new environment.
This method is preferred because it has the most flexibility and potential to maintain
the meta data associated with each commit.
</p><p>
When a direct import mechanism is not available, it is still possible to
export a branch (or series of branches) and check them into a new repository.
</p><p>
The following commands illustrate some of the steps you could use to
import the <code class="filename">yocto/standard/common-pc/base</code>
kernel into a secondary SCM:
</p><pre class="literallayout">
$ git checkout yocto/standard/common-pc/base
$ cd .. ; echo linux/.git &gt; .cvsignore
$ cvs import -m "initial import" linux MY_COMPANY start
</pre><p>
</p><p>
You could now relocate the CVS repository and use it in a centralized manner.
</p><p>
The following commands illustrate how you can condense and merge two BSPs into a
second SCM:
</p><pre class="literallayout">
$ git checkout yocto/standard/common-pc/base
$ git merge yocto/standard/common-pc-64/base
# resolve any conflicts and commit them
$ cd .. ; echo linux/.git &gt; .cvsignore
$ cvs import -m "initial import" linux MY_COMPANY start
</pre><p>
</p></div><div class="section" title="3.4.3.2. Importing Changes for the Build"><div class="titlepage"><div><div><h4 class="title"><a id="importing-changes-for-build"></a>3.4.3.2. Importing Changes for the Build</h4></div></div></div><p>
Once development has reached a suitable point in the second development
environment, you need to export the changes as patches.
To export them, place the changes in a recipe and
automatically apply them to the kernel during patching.
</p></div></div><div class="section" title="3.4.4. Creating a BSP Based on an Existing Similar BSP"><div class="titlepage"><div><div><h3 class="title"><a id="bsp-creating"></a>3.4.4. Creating a BSP Based on an Existing Similar BSP</h3></div></div></div><p>
This section overviews the process of creating a BSP based on an
existing similar BSP.
The information is introductory in nature and does not provide step-by-step examples.
For detailed information on how to create a BSP given an existing similar BSP, see
the "<a class="link" href="#dev-manual-bsp-appendix" target="_top">BSP Development
Example</a>" appendix in the Yocto Project Development Manual, or see the
<a class="ulink" href="https://wiki.yoctoproject.org/wiki/Transcript:_creating_one_generic_Atom_BSP_from_another" target="_top">Transcript:_creating_one_generic_Atom_BSP_from_another</a>
wiki page.
</p><p>
The basic steps you need to follow are:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p><span class="emphasis"><em>Make sure you have set up a local source directory:</em></span>
You must create a local <a class="link" href="#source-directory" target="_top">source
directory</a> by either creating a Git repository (recommended) or
extracting a Yocto Project release tarball.</p></li><li class="listitem"><p><span class="emphasis"><em>Choose an existing BSP available with the Yocto Project:</em></span>
Try to map your board features as closely to the features of a BSP that is
already supported and exists in the Yocto Project.
Starting with something as close as possible to your board makes developing
your BSP easier.
You can find all the BSPs that are supported and ship with the Yocto Project
on the Yocto Project's Download page at
<a class="ulink" href="http://www.yoctoproject.org/download" target="_top">http://www.yoctoproject.org/download</a>.</p></li><li class="listitem"><p><span class="emphasis"><em>Be sure you have the Base BSP:</em></span>
You need to either have a local Git repository of the base BSP set up or
have downloaded and extracted the files from a release BSP tarball.
Either method gives you access to the BSP source files.</p></li><li class="listitem"><p><span class="emphasis"><em>Make a copy of the existing BSP, thus isolating your new
BSP work:</em></span>
Copying the existing BSP file structure gives you a new area in which to work.</p></li><li class="listitem"><p><span class="emphasis"><em>Make configuration and recipe changes to your new BSP:</em></span>
Configuration changes involve the files in the BSP's <code class="filename">conf</code>
directory.
Changes include creating a machine-specific configuration file and editing the
<code class="filename">layer.conf</code> file.
The configuration changes identify the kernel you will be using.
Recipe changes include removing, modifying, or adding new recipe files that
instruct the build process on what features to include in the image.</p></li><li class="listitem"><p><span class="emphasis"><em>Prepare for the build:</em></span>
Before you actually initiate the build, you need to set up the build environment
by sourcing the environment initialization script.
After setting up the environment, you need to make some build configuration
changes to the <code class="filename">local.conf</code> and <code class="filename">bblayers.conf</code>
files.</p></li><li class="listitem"><p><span class="emphasis"><em>Build the image:</em></span>
The OpenEmbedded build system uses BitBake to create the image.
You need to decide on the type of image you are going to build (e.g. minimal, base,
core, sato, and so forth) and then start the build using the <code class="filename">bitbake</code>
command.</p></li></ol></div><p>
</p></div><div class="section" title="3.4.5. &quot;-dirty&quot; String"><div class="titlepage"><div><div><h3 class="title"><a id="tip-dirty-string"></a>3.4.5. "-dirty" String</h3></div></div></div><p>
If kernel images are being built with "-dirty" on the end of the version
string, this simply means that modifications in the source
directory have not been committed.
</p><pre class="literallayout">
$ git status
</pre><p>
</p><p>
You can use the above Git command to report modified, removed, or added files.
You should commit those changes to the tree regardless of whether they will be saved,
exported, or used.
Once you commit the changes you need to rebuild the kernel.
</p><p>
To brute force pickup and commit all such pending changes, enter the following:
</p><pre class="literallayout">
$ git add .
$ git commit -s -a -m "getting rid of -dirty"
</pre><p>
</p><p>
Next, rebuild the kernel.
</p></div></div></div>
</div>
<table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="100%"><tr><td align="left"><img src="figures/poky-title.png" align="left" width="100%" /></td></tr></table>
<div xml:lang="en" class="book" lang="en"><div class="titlepage"><div><div><h1 class="title"><a id="poky-ref-manual"></a></h1></div><div><div class="authorgroup">
<div class="author"><h3 class="author"><span class="firstname">Richard</span> <span class="surname">Purdie</span></h3><div class="affiliation">
<span class="orgname">Linux Foundation<br /></span>
</div><code class="email">&lt;<a class="email" href="mailto:richard.purdie@linuxfoundation.org">richard.purdie@linuxfoundation.org</a>&gt;</code></div>
</div></div><div><p class="copyright">Copyright © 2010-2012 Linux Foundation</p></div><div><div class="legalnotice" title="Legal Notice"><a id="id1506919"></a>
<p>
Permission is granted to copy, distribute and/or modify this document under
the terms of the <a class="ulink" href="http://creativecommons.org/licenses/by-sa/2.0/uk/" target="_top">Creative Commons Attribution-Share Alike 2.0 UK: England &amp; Wales</a> as published by Creative Commons.
</p>
<div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Due to production processes, there could be differences between the Yocto Project
documentation bundled in the release tarball and the
Yocto Project Reference Manual on
the <a class="ulink" href="http://www.yoctoproject.org" target="_top">Yocto Project</a> website.
For the latest version of this manual, see the manual on the website.
</div>
</div></div><div><div class="revhistory"><table border="1" width="100%" summary="Revision history"><tr><th align="left" valign="top" colspan="2"><b>Revision History</b></th></tr>
<tr><td align="left">Revision 4.0+git</td><td align="left">24 November 2010</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 0.9 Release</td></tr>
<tr><td align="left">Revision 1.0</td><td align="left">6 April 2011</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.0 Release.</td></tr>
<tr><td align="left">Revision 1.0.1</td><td align="left">23 May 2011</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.0.1 Release.</td></tr>
<tr><td align="left">Revision 1.1</td><td align="left">6 October 2011</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.1 Release.</td></tr>
<tr><td align="left">Revision 1.2</td><td align="left">April 2012</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.2 Release.</td></tr>
<tr><td align="left">Revision 1.3</td><td align="left">Sometime in 2012</td></tr><tr><td align="left" colspan="2">Released with the Yocto Project 1.3 Release.</td></tr>
</table></div></div></div><hr /></div>
<div class="chapter" title="Chapter 1. Introduction"><div class="titlepage"><div><div><h2 class="title"><a id="intro"></a>Chapter 1. Introduction</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#intro-welcome">1.1. Introduction</a></span></dt><dt><span class="section"><a href="#intro-manualoverview">1.2. Documentation Overview</a></span></dt><dt><span class="section"><a href="#intro-requirements">1.3. System Requirements</a></span></dt><dt><span class="section"><a href="#intro-getit">1.4. Obtaining the Yocto Project</a></span></dt><dt><span class="section"><a href="#intro-getit-dev">1.5. Development Checkouts</a></span></dt></dl></div><div class="section" title="1.1. Introduction"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="intro-welcome"></a>1.1. Introduction</h2></div></div></div><p>
This manual provides reference information for the current release of the Yocto Project.
The Yocto Project is an open-source collaboration project focused on embedded Linux
developers.
Amongst other things, the Yocto Project uses the OpenEmbedded build system, which
is based on the Poky project, to construct complete Linux images.
You can find complete introductory and getting started information on the Yocto Project
by reading the
Yocto Project Quick Start.
For task-based information using the Yocto Project, see the
Yocto Project Development Manual.
You can also find lots of information on the Yocto Project on the
<a class="ulink" href="http://www.yoctoproject.org" target="_top">Yocto Project website</a>.
</p></div><div class="section" title="1.2. Documentation Overview"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="intro-manualoverview"></a>1.2. Documentation Overview</h2></div></div></div><p>
This reference manual consists of the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>
<a class="link" href="#usingpoky" title="Chapter 2. Using the Yocto Project">Using the Yocto Project</a>:</em></span> This chapter
provides an overview of the components that make up the Yocto Project
followed by information about debugging images created in the Yocto Project.
</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="link" href="#technical-details" title="Chapter 3. Technical Details">Technical Details</a>:</em></span>
This chapter describes fundamental Yocto Project components as well as an explanation
behind how the Yocto Project uses shared state (sstate) cache to speed build time.
</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="link" href="#ref-structure" title="Chapter 4. Source Directory Structure">Directory Structure</a>:</em></span>
This chapter describes the
<a class="link" href="#source-directory" target="_top">source directory</a> created
either by unpacking a released Yocto Project tarball on your host development system,
or by cloning the upstream
<a class="link" href="#poky" target="_top">Poky</a> Git repository.
</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="link" href="#ref-bitbake" title="Chapter 5. BitBake">BitBake</a>:</em></span>
This chapter provides an overview of the BitBake tool and its role within
the Yocto Project.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="link" href="#ref-classes" title="Chapter 6. Classes">Classes</a>:</em></span>
This chapter describes the classes used in the Yocto Project.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="link" href="#ref-images" title="Chapter 7. Images">Images</a>:</em></span>
This chapter describes the standard images that the Yocto Project supports.
</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="link" href="#ref-features" title="Chapter 8. Reference: Features">Features</a>:</em></span>
This chapter describes mechanisms for creating distribution, machine, and image
features during the build process using the OpenEmbedded build system.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="link" href="#ref-variables-glos" title="Chapter 9. Variables Glossary">Variables Glossary</a>:</em></span>
This chapter presents most variables used by the OpenEmbedded build system, which
using BitBake.
Entries describe the function of the variable and how to apply them.
</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="link" href="#ref-varlocality" title="Chapter 10. Variable Context">Variable Context</a>:</em></span>
This chapter provides variable locality or context.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="link" href="#faq" title="Chapter 11. FAQ">FAQ</a>:</em></span>
This chapter provides answers for commonly asked questions in the Yocto Project
development environment.</p></li><li class="listitem"><p><span class="emphasis"><em>
<a class="link" href="#resources" title="Chapter 12. Contributing to the Yocto Project">Contributing to the Yocto Project</a>:</em></span>
This chapter provides guidance on how you can contribute back to the Yocto
Project.</p></li></ul></div><p>
</p></div><div class="section" title="1.3. System Requirements"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="intro-requirements"></a>1.3. System Requirements</h2></div></div></div><p>
For Yocto Project system requirements, see the
<a class="link" href="#yp-resources" target="_top">
What You Need and How You Get It</a> section in the Yocto Project Quick Start.
</p></div><div class="section" title="1.4. Obtaining the Yocto Project"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="intro-getit"></a>1.4. Obtaining the Yocto Project</h2></div></div></div><p>
The Yocto Project development team makes the Yocto Project available through a number
of methods:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Releases:</em></span> Stable, tested releases are available through
<a class="ulink" href="http://downloads.yoctoproject.org/releases/yocto/" target="_top">http://downloads.yoctoproject.org/releases/yocto/</a>.</p></li><li class="listitem"><p><span class="emphasis"><em>Nightly Builds:</em></span> These releases are available at
<a class="ulink" href="http://autobuilder.yoctoproject.org/nightly" target="_top">http://autobuilder.yoctoproject.org/nightly</a>.
These builds include Yocto Project releases, meta-toolchain tarballs, and
experimental builds.</p></li><li class="listitem"><p><span class="emphasis"><em>Yocto Project Website:</em></span> You can find releases
of the Yocto Project and supported BSPs at the
<a class="ulink" href="http://www.yoctoproject.org" target="_top">Yocto Project website</a>.
Along with these downloads, you can find lots of other information at this site.
</p></li></ul></div><p>
</p></div><div class="section" title="1.5. Development Checkouts"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="intro-getit-dev"></a>1.5. Development Checkouts</h2></div></div></div><p>
Development using the Yocto Project requires a local
<a class="link" href="#source-directory" target="_top">source directory</a>.
You can set up the source directory by downloading a Yocto Project release tarball and unpacking it,
or by cloning a copy of the upstream
<a class="link" href="#poky" target="_top">Poky</a> Git repository.
For information on both these methods, see the
"<a class="link" href="#getting-setup" target="_top">Getting Setup</a>"
section in the Yocto Project Development Manual.
</p></div></div>
<div class="chapter" title="Chapter 2. Using the Yocto Project"><div class="titlepage"><div><div><h2 class="title"><a id="usingpoky"></a>Chapter 2. Using the Yocto Project</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#usingpoky-build">2.1. Running a Build</a></span></dt><dd><dl><dt><span class="section"><a href="#build-overview">2.1.1. Build Overview</a></span></dt><dt><span class="section"><a href="#building-an-image-using-gpl-components">2.1.2. Building an Image Using GPL Components</a></span></dt></dl></dd><dt><span class="section"><a href="#usingpoky-install">2.2. Installing and Using the Result</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging">2.3. Debugging Build Failures</a></span></dt><dd><dl><dt><span class="section"><a href="#usingpoky-debugging-taskfailures">2.3.1. Task Failures</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-taskrunning">2.3.2. Running Specific Tasks</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-dependencies">2.3.3. Dependency Graphs</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-bitbake">2.3.4. General BitBake Problems</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-buildfile">2.3.5. Building with No Dependencies</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-variables">2.3.6. Variables</a></span></dt><dt><span class="section"><a href="#recipe-logging-mechanisms">2.3.7. Recipe Logging Mechanisms</a></span></dt><dt><span class="section"><a href="#usingpoky-debugging-others">2.3.8. Other Tips</a></span></dt></dl></dd></dl></div><p>
This chapter describes common usage for the Yocto Project.
The information is introductory in nature as other manuals in the Yocto Project
documentation set provide more details on how to use the Yocto Project.
</p><div class="section" title="2.1. Running a Build"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="usingpoky-build"></a>2.1. Running a Build</h2></div></div></div><p>
You can find general information on how to build an image using the OpenEmbedded build
system in the
"<a class="link" href="#building-image" target="_top">Building an Image</a>"
section of the Yocto Project Quick Start.
This section provides a summary of the build process and provides information
for less obvious aspects of the build process.
</p><div class="section" title="2.1.1. Build Overview"><div class="titlepage"><div><div><h3 class="title"><a id="build-overview"></a>2.1.1. Build Overview</h3></div></div></div><p>
The first thing you need to do is set up the OpenEmbedded build environment by sourcing
the environment setup script as follows:
</p><pre class="literallayout">
$ source oe-init-build-env [build_dir]
</pre><p>
</p><p>
The <code class="filename">build_dir</code> is optional and specifies the directory the
OpenEmbedded build system uses for the build -
the <a class="link" href="#build-directory" target="_top">build directory</a>.
If you do not specify a build directory it defaults to <code class="filename">build</code>
in your current working directory.
A common practice is to use a different build directory for different targets.
For example, <code class="filename">~/build/x86</code> for a <code class="filename">qemux86</code>
target, and <code class="filename">~/build/arm</code> for a <code class="filename">qemuarm</code> target.
See <a class="link" href="#structure-core-script" title="4.1.9. oe-init-build-env">oe-init-build-env</a>
for more information on this script.
</p><p>
Once the build environment is set up, you can build a target using:
</p><pre class="literallayout">
$ bitbake &lt;target&gt;
</pre><p>
</p><p>
The <code class="filename">target</code> is the name of the recipe you want to build.
Common targets are the images in <code class="filename">meta/recipes-core/images</code>,
<code class="filename">/meta/recipes-sato/images</code>, etc. all found in the
<a class="link" href="#source-directory" target="_top">source directory</a>.
Or, the target can be the name of a recipe for a specific piece of software such as
<span class="application">busybox</span>.
For more details about the images the OpenEmbedded build system supports, see the
"<a class="link" href="#ref-images" title="Chapter 7. Images">Images</a>" chapter.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Building an image without GNU Public License Version 3 (GPLv3) components is
only supported for minimal and base images.
See the "<a class="link" href="#ref-images" title="Chapter 7. Images">Images</a>" chapter for more information.
</div></div><div class="section" title="2.1.2. Building an Image Using GPL Components"><div class="titlepage"><div><div><h3 class="title"><a id="building-an-image-using-gpl-components"></a>2.1.2. Building an Image Using GPL Components</h3></div></div></div><p>
When building an image using GPL components, you need to maintain your original
settings and not switch back and forth applying different versions of the GNU
Public License.
If you rebuild using different versions of GPL, dependency errors might occur
due to some components not being rebuilt.
</p></div></div><div class="section" title="2.2. Installing and Using the Result"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="usingpoky-install"></a>2.2. Installing and Using the Result</h2></div></div></div><p>
Once an image has been built, it often needs to be installed.
The images and kernels built by the OpenEmbedded build system are placed in the
<a class="link" href="#build-directory" target="_top">build directory</a> in
<code class="filename">tmp/deploy/images</code>.
For information on how to run pre-built images such as <code class="filename">qemux86</code>
and <code class="filename">qemuarm</code>, see the
"<a class="link" href="#using-pre-built" target="_top">Using Pre-Built Binaries and QEMU</a>"
section in the Yocto Project Quick Start.
For information about how to install these images, see the documentation for your
particular board/machine.
</p></div><div class="section" title="2.3. Debugging Build Failures"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="usingpoky-debugging"></a>2.3. Debugging Build Failures</h2></div></div></div><p>
The exact method for debugging build failures depends on the nature of the
problem and on the system's area from which the bug originates.
Standard debugging practices such as comparison against the last
known working version with examination of the changes and the re-application of steps
to identify the one causing the problem are
valid for the Yocto Project just as they are for any other system.
Even though it is impossible to detail every possible potential failure,
this section provides some general tips to aid in debugging.
</p><div class="section" title="2.3.1. Task Failures"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-debugging-taskfailures"></a>2.3.1. Task Failures</h3></div></div></div><p>The log file for shell tasks is available in
<code class="filename">${WORKDIR}/temp/log.do_taskname.pid</code>.
For example, the <code class="filename">compile</code> task for the QEMU minimal image for the x86
machine (<code class="filename">qemux86</code>) might be
<code class="filename">tmp/work/qemux86-poky-linux/core-image-minimal-1.0-r0/temp/log.do_compile.20830</code>.
To see what BitBake runs to generate that log, look at the corresponding
<code class="filename">run.do_taskname.pid</code> file located in the same directory.
</p><p>
Presently, the output from Python tasks is sent directly to the console.
</p></div><div class="section" title="2.3.2. Running Specific Tasks"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-debugging-taskrunning"></a>2.3.2. Running Specific Tasks</h3></div></div></div><p>
Any given package consists of a set of tasks.
The standard BitBake behavior in most cases is: <code class="filename">fetch</code>,
<code class="filename">unpack</code>,
<code class="filename">patch</code>, <code class="filename">configure</code>,
<code class="filename">compile</code>, <code class="filename">install</code>, <code class="filename">package</code>,
<code class="filename">package_write</code>, and <code class="filename">build</code>.
The default task is <code class="filename">build</code> and any tasks on which it depends
build first.
Some tasks exist, such as <code class="filename">devshell</code>, that are not part of the
default build chain.
If you wish to run a task that is not part of the default build chain, you can use the
<code class="filename">-c</code> option in BitBake as follows:
</p><pre class="literallayout">
$ bitbake matchbox-desktop -c devshell
</pre><p>
</p><p>
If you wish to rerun a task, use the <code class="filename">-f</code> force option.
For example, the following sequence forces recompilation after changing files in the
working directory.
</p><pre class="literallayout">
$ bitbake matchbox-desktop
.
.
[make some changes to the source code in the working directory]
.
.
$ bitbake matchbox-desktop -c compile -f
$ bitbake matchbox-desktop
</pre><p>
</p><p>
This sequence first builds <code class="filename">matchbox-desktop</code> and then recompiles it.
The last command reruns all tasks (basically the packaging tasks) after the compile.
BitBake recognizes that the <code class="filename">compile</code> task was rerun and therefore
understands that the other tasks also need to be run again.
</p><p>
You can view a list of tasks in a given package by running the
<code class="filename">listtasks</code> task as follows:
</p><pre class="literallayout">
$ bitbake matchbox-desktop -c listtasks
</pre><p>
The results are in the file <code class="filename">${WORKDIR}/temp/log.do_listtasks</code>.
</p></div><div class="section" title="2.3.3. Dependency Graphs"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-debugging-dependencies"></a>2.3.3. Dependency Graphs</h3></div></div></div><p>
Sometimes it can be hard to see why BitBake wants to build some other packages before a given
package you have specified.
The <code class="filename">bitbake -g targetname</code> command creates the
<code class="filename">depends.dot</code>, <code class="filename">package-depends.dot</code>,
and <code class="filename">task-depends.dot</code> files in the current directory.
These files show the package and task dependencies and are useful for debugging problems.
You can use the <code class="filename">bitbake -g -u depexp targetname</code> command to
display the results in a more human-readable form.
</p></div><div class="section" title="2.3.4. General BitBake Problems"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-debugging-bitbake"></a>2.3.4. General BitBake Problems</h3></div></div></div><p>
You can see debug output from BitBake by using the <code class="filename">-D</code> option.
The debug output gives more information about what BitBake
is doing and the reason behind it.
Each <code class="filename">-D</code> option you use increases the logging level.
The most common usage is <code class="filename">-DDD</code>.
</p><p>
The output from <code class="filename">bitbake -DDD -v targetname</code> can reveal why
BitBake chose a certain version of a package or why BitBake
picked a certain provider.
This command could also help you in a situation where you think BitBake did something
unexpected.
</p></div><div class="section" title="2.3.5. Building with No Dependencies"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-debugging-buildfile"></a>2.3.5. Building with No Dependencies</h3></div></div></div><p>
If you really want to build a specific <code class="filename">.bb</code> file, you can use
the command form <code class="filename">bitbake -b &lt;somepath/somefile.bb&gt;</code>.
This command form does not check for dependencies so you should use it
only when you know its dependencies already exist.
You can also specify fragments of the filename.
In this case, BitBake checks for a unique match.
</p></div><div class="section" title="2.3.6. Variables"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-debugging-variables"></a>2.3.6. Variables</h3></div></div></div><p>
The <code class="filename">-e</code> option dumps the resulting environment for
either the configuration (no package specified) or for a
specific package when specified; or <code class="filename">-b recipename</code>
to show the environment from parsing a single recipe file only.
</p></div><div class="section" title="2.3.7. Recipe Logging Mechanisms"><div class="titlepage"><div><div><h3 class="title"><a id="recipe-logging-mechanisms"></a>2.3.7. Recipe Logging Mechanisms</h3></div></div></div><p>
Best practices exist while writing recipes that both log build progress and
act on build conditions such as warnings and errors.
Both Python and Bash language bindings exist for the logging mechanism:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Python:</em></span> For Python functions, BitBake
supports several loglevels: <code class="filename">bb.fatal</code>,
<code class="filename">bb.error</code>, <code class="filename">bb.warn</code>,
<code class="filename">bb.note</code>, <code class="filename">bb.plain</code>,
and <code class="filename">bb.debug</code>.</p></li><li class="listitem"><p><span class="emphasis"><em>Bash:</em></span> For Bash functions, the same set
of loglevels exist and are accessed with a similar syntax:
<code class="filename">bbfatal</code>, <code class="filename">bberror</code>,
<code class="filename">bbwarn</code>, <code class="filename">bbnote</code>,
<code class="filename">bbplain</code>, and <code class="filename">bbdebug</code>.</p></li></ul></div><p>
</p><p>
For guidance on how logging is handled in both Python and Bash recipes, see the
<code class="filename">logging.bbclass</code> file in the
<code class="filename">meta/classes</code> folder of the
<a class="link" href="#source-directory" target="_top">source directory</a>.
</p><div class="section" title="2.3.7.1. Logging With Python"><div class="titlepage"><div><div><h4 class="title"><a id="logging-with-python"></a>2.3.7.1. Logging With Python</h4></div></div></div><p>
When creating recipes using Python and inserting code that handles build logs
keep in mind the goal is to have informative logs while keeping the console as
"silent" as possible.
Also, if you want status messages in the log use the "debug" loglevel.
</p><p>
Following is an example written in Python.
The code handles logging for a function that determines the number of tasks
needed to be run:
</p><pre class="literallayout">
python do_listtasks() {
bb.debug(2, "Starting to figure out the task list")
if noteworthy_condition:
bb.note("There are 47 tasks to run")
bb.debug(2, "Got to point xyz")
if warning_trigger:
bb.warn("Detected warning_trigger, this might be a problem later.")
if recoverable_error:
bb.error("Hit recoverable_error, you really need to fix this!")
if fatal_error:
bb.fatal("fatal_error detected, unable to print the task list")
bb.plain("The tasks present are abc")
bb.debug(2, "Finished figuring out the tasklist")
}
</pre><p>
</p></div><div class="section" title="2.3.7.2. Logging With Bash"><div class="titlepage"><div><div><h4 class="title"><a id="logging-with-bash"></a>2.3.7.2. Logging With Bash</h4></div></div></div><p>
When creating recipes using Bash and inserting code that handles build
logs you have the same goals - informative with minimal console output.
The syntax you use for recipes written in Bash is similar to that of
recipes written in Python described in the previous section.
</p><p>
Following is an example written in Bash.
The code logs the progress of the <code class="filename">do_my_function</code> function.
</p><pre class="literallayout">
do_my_function() {
bbdebug 2 "Running do_my_function"
if [ exceptional_condition ]; then
bbnote "Hit exceptional_condition"
fi
bbdebug 2 "Got to point xyz"
if [ warning_trigger ]; then
bbwarn "Detected warning_trigger, this might cause a problem later."
fi
if [ recoverable_error ]; then
bberror "Hit recoverable_error, correcting"
fi
if [ fatal_error ]; then
bbfatal "fatal_error detected"
fi
bbdebug 2 "Completed do_my_function"
}
</pre><p>
</p></div></div><div class="section" title="2.3.8. Other Tips"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-debugging-others"></a>2.3.8. Other Tips</h3></div></div></div><p>
Here are some other tips that you might find useful:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>When adding new packages, it is worth watching for
undesirable items making their way into compiler command lines.
For example, you do not want references to local system files like
<code class="filename">/usr/lib/</code> or <code class="filename">/usr/include/</code>.
</p></li><li class="listitem"><p>If you want to remove the psplash boot splashscreen,
add <code class="filename">psplash=false</code> to the kernel command line.
Doing so prevents psplash from loading and thus allows you to see the console.
It is also possible to switch out of the splashscreen by
switching the virtual console (e.g. Fn+Left or Fn+Right on a Zaurus).
</p></li></ul></div><p>
</p></div></div></div>
<div class="chapter" title="Chapter 3. Technical Details"><div class="titlepage"><div><div><h2 class="title"><a id="technical-details"></a>Chapter 3. Technical Details</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#usingpoky-components">3.1. Yocto Project Components</a></span></dt><dd><dl><dt><span class="section"><a href="#usingpoky-components-bitbake">3.1.1. BitBake</a></span></dt><dt><span class="section"><a href="#usingpoky-components-metadata">3.1.2. Metadata (Recipes)</a></span></dt><dt><span class="section"><a href="#usingpoky-components-classes">3.1.3. Classes</a></span></dt><dt><span class="section"><a href="#usingpoky-components-configuration">3.1.4. Configuration</a></span></dt></dl></dd><dt><span class="section"><a href="#shared-state-cache">3.2. Shared State Cache</a></span></dt><dd><dl><dt><span class="section"><a href="#overall-architecture">3.2.1. Overall Architecture</a></span></dt><dt><span class="section"><a href="#checksums">3.2.2. Checksums (Signatures)</a></span></dt><dt><span class="section"><a href="#shared-state">3.2.3. Shared State</a></span></dt><dt><span class="section"><a href="#tips-and-tricks">3.2.4. Tips and Tricks</a></span></dt></dl></dd><dt><span class="section"><a href="#x32">3.3. x32</a></span></dt><dd><dl><dt><span class="section"><a href="#support">3.3.1. Support</a></span></dt><dt><span class="section"><a href="#future-development-and-limitations">3.3.2. Future Development and Limitations</a></span></dt><dt><span class="section"><a href="#using-x32-right-now">3.3.3. Using x32 Right Now</a></span></dt></dl></dd><dt><span class="section"><a href="#licenses">3.4. Licenses</a></span></dt><dd><dl><dt><span class="section"><a href="#usingpoky-configuring-LIC_FILES_CHKSUM">3.4.1. Tracking License Changes</a></span></dt><dt><span class="section"><a href="#enabling-commercially-licensed-recipes">3.4.2. Enabling Commercially Licensed Recipes</a></span></dt></dl></dd></dl></div><p>
This chapter provides technical details for various parts of the Yocto Project.
Currently, topics include Yocto Project components and shared state (sstate) cache.
</p><div class="section" title="3.1. Yocto Project Components"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="usingpoky-components"></a>3.1. Yocto Project Components</h2></div></div></div><p>
The BitBake task executor together with various types of configuration files form the
OpenEmbedded Core.
This section overviews the BitBake task executor and the
configuration files by describing what they are used for and how they interact.
</p><p>
BitBake handles the parsing and execution of the data files.
The data itself is of various types:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Recipes:</em></span> Provides details about particular
pieces of software</p></li><li class="listitem"><p><span class="emphasis"><em>Class Data:</em></span> An abstraction of common build
information (e.g. how to build a Linux kernel).</p></li><li class="listitem"><p><span class="emphasis"><em>Configuration Data:</em></span> Defines machine-specific settings,
policy decisions, etc.
Configuration data acts as the glue to bind everything together.</p></li></ul></div><p>
For more information on data, see the
"<a class="link" href="#yocto-project-terms" target="_top">Yocto Project Terms</a>"
section in the Yocto Project Development Manual.
</p><p>
BitBake knows how to combine multiple data sources together and refers to each data source
as a layer.
For information on layers, see the
"<a class="link" href="#understanding-and-creating-layers" target="_top">Understanding and
Creating Layers</a>" section of the Yocto Project Development Manual.
</p><p>
Following are some brief details on these core components.
For more detailed information on these components see the
"<a class="link" href="#ref-structure" title="Chapter 4. Source Directory Structure">Directory Structure</a>" chapter.
</p><div class="section" title="3.1.1. BitBake"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-components-bitbake"></a>3.1.1. BitBake</h3></div></div></div><p>
BitBake is the tool at the heart of the OpenEmbedded build system and is responsible
for parsing the metadata, generating a list of tasks from it,
and then executing those tasks.
To see a list of the options BitBake supports, use the following help command:
</p><pre class="literallayout">
$ bitbake --help
</pre><p>
</p><p>
The most common usage for BitBake is <code class="filename">bitbake &lt;packagename&gt;</code>, where
<code class="filename">packagename</code> is the name of the package you want to build
(referred to as the "target" in this manual).
The target often equates to the first part of a <code class="filename">.bb</code> filename.
So, to run the <code class="filename">matchbox-desktop_1.2.3.bb</code> file, you
might type the following:
</p><pre class="literallayout">
$ bitbake matchbox-desktop
</pre><p>
Several different versions of <code class="filename">matchbox-desktop</code> might exist.
BitBake chooses the one selected by the distribution configuration.
You can get more details about how BitBake chooses between different
target versions and providers in the
"<a class="link" href="#ref-bitbake-providers" title="5.2. Preferences and Providers">Preferences and Providers</a>" section.
</p><p>
BitBake also tries to execute any dependent tasks first.
So for example, before building <code class="filename">matchbox-desktop</code>, BitBake
would build a cross compiler and <code class="filename">eglibc</code> if they had not already
been built.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>This release of the Yocto Project does not support the <code class="filename">glibc</code>
GNU version of the Unix standard C library. By default, the OpenEmbedded build system
builds with <code class="filename">eglibc</code>.</div><p>
</p><p>
A useful BitBake option to consider is the <code class="filename">-k</code> or
<code class="filename">--continue</code> option.
This option instructs BitBake to try and continue processing the job as much
as possible even after encountering an error.
When an error occurs, the target that
failed and those that depend on it cannot be remade.
However, when you use this option other dependencies can still be processed.
</p></div><div class="section" title="3.1.2. Metadata (Recipes)"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-components-metadata"></a>3.1.2. Metadata (Recipes)</h3></div></div></div><p>
The <code class="filename">.bb</code> files are usually referred to as "recipes."
In general, a recipe contains information about a single piece of software.
The information includes the location from which to download the source patches
(if any are needed), which special configuration options to apply,
how to compile the source files, and how to package the compiled output.
</p><p>
The term "package" can also be used to describe recipes.
However, since the same word is used for the packaged output from the OpenEmbedded
build system (i.e. <code class="filename">.ipk</code> or <code class="filename">.deb</code> files),
this document avoids using the term "package" when referring to recipes.
</p></div><div class="section" title="3.1.3. Classes"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-components-classes"></a>3.1.3. Classes</h3></div></div></div><p>
Class files (<code class="filename">.bbclass</code>) contain information that is useful to share
between metadata files.
An example is the Autotools class, which contains
common settings for any application that Autotools uses.
The "<a class="link" href="#ref-classes" title="Chapter 6. Classes">Reference: Classes</a>" chapter provides details
about common classes and how to use them.
</p></div><div class="section" title="3.1.4. Configuration"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-components-configuration"></a>3.1.4. Configuration</h3></div></div></div><p>
The configuration files (<code class="filename">.conf</code>) define various configuration variables
that govern the OpenEmbedded build process.
These files fall into several areas that define machine configuration options,
distribution configuration options, compiler tuning options, general common configuration
options and user configuration options (<code class="filename">local.conf</code>, which is found
in the <a class="ulink" href="build-directory" target="_top">build directory</a>).
</p></div></div><div class="section" title="3.2. Shared State Cache"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="shared-state-cache"></a>3.2. Shared State Cache</h2></div></div></div><p>
By design, the OpenEmbedded build system builds everything from scratch unless
BitBake can determine that parts don't need to be rebuilt.
Fundamentally, building from scratch is attractive as it means all parts are
built fresh and there is no possibility of stale data causing problems.
When developers hit problems, they typically default back to building from scratch
so they know the state of things from the start.
</p><p>
Building an image from scratch is both an advantage and a disadvantage to the process.
As mentioned in the previous paragraph, building from scratch ensures that
everything is current and starts from a known state.
However, building from scratch also takes much longer as it generally means
rebuilding things that don't necessarily need rebuilt.
</p><p>
The Yocto Project implements shared state code that supports incremental builds.
The implementation of the shared state code answers the following questions that
were fundamental roadblocks within the OpenEmbedded incremental build support system:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">What pieces of the system have changed and what pieces have not changed?</li><li class="listitem">How are changed pieces of software removed and replaced?</li><li class="listitem">How are pre-built components that don't need to be rebuilt from scratch
used when they are available?</li></ul></div><p>
</p><p>
For the first question, the build system detects changes in the "inputs" to a given task by
creating a checksum (or signature) of the task's inputs.
If the checksum changes, the system assumes the inputs have changed and the task needs to be
rerun.
For the second question, the shared state (sstate) code tracks which tasks add which output
to the build process.
This means the output from a given task can be removed, upgraded or otherwise manipulated.
The third question is partly addressed by the solution for the second question
assuming the build system can fetch the sstate objects from remote locations and
install them if they are deemed to be valid.
</p><p>
The rest of this section goes into detail about the overall incremental build
architecture, the checksums (signatures), shared state, and some tips and tricks.
</p><div class="section" title="3.2.1. Overall Architecture"><div class="titlepage"><div><div><h3 class="title"><a id="overall-architecture"></a>3.2.1. Overall Architecture</h3></div></div></div><p>
When determining what parts of the system need to be built, BitBake
uses a per-task basis and does not use a per-recipe basis.
You might wonder why using a per-task basis is preferred over a per-recipe basis.
To help explain, consider having the IPK packaging backend enabled and then switching to DEB.
In this case, <code class="filename">do_install</code> and <code class="filename">do_package</code>
output are still valid.
However, with a per-recipe approach, the build would not include the
<code class="filename">.deb</code> files.
Consequently, you would have to invalidate the whole build and rerun it.
Rerunning everything is not the best situation.
Also in this case, the core must be "taught" much about specific tasks.
This methodology does not scale well and does not allow users to easily add new tasks
in layers or as external recipes without touching the packaged-staging core.
</p></div><div class="section" title="3.2.2. Checksums (Signatures)"><div class="titlepage"><div><div><h3 class="title"><a id="checksums"></a>3.2.2. Checksums (Signatures)</h3></div></div></div><p>
The shared state code uses a checksum, which is a unique signature of a task's
inputs, to determine if a task needs to be run again.
Because it is a change in a task's inputs that triggers a rerun, the process
needs to detect all the inputs to a given task.
For shell tasks, this turns out to be fairly easy because
the build process generates a "run" shell script for each task and
it is possible to create a checksum that gives you a good idea of when
the task's data changes.
</p><p>
To complicate the problem, there are things that should not be included in
the checksum.
First, there is the actual specific build path of a given task -
the <code class="filename">WORKDIR</code>.
It does not matter if the working directory changes because it should not
affect the output for target packages.
Also, the build process has the objective of making native/cross packages relocatable.
The checksum therefore needs to exclude <code class="filename">WORKDIR</code>.
The simplistic approach for excluding the working directory is to set
<code class="filename">WORKDIR</code> to some fixed value and create the checksum
for the "run" script.
</p><p>
Another problem results from the "run" scripts containing functions that
might or might not get called.
The incremental build solution contains code that figures out dependencies
between shell functions.
This code is used to prune the "run" scripts down to the minimum set,
thereby alleviating this problem and making the "run" scripts much more
readable as a bonus.
</p><p>
So far we have solutions for shell scripts.
What about python tasks?
The same approach applies even though these tasks are more difficult.
The process needs to figure out what variables a python function accesses
and what functions it calls.
Again, the incremental build solution contains code that first figures out
the variable and function dependencies, and then creates a checksum for the data
used as the input to the task.
</p><p>
Like the <code class="filename">WORKDIR</code> case, situations exist where dependencies
should be ignored.
For these cases, you can instruct the build process to ignore a dependency
by using a line like the following:
</p><pre class="literallayout">
PACKAGE_ARCHS[vardepsexclude] = "MACHINE"
</pre><p>
This example ensures that the <code class="filename">PACKAGE_ARCHS</code> variable does not
depend on the value of <code class="filename">MACHINE</code>, even if it does reference it.
</p><p>
Equally, there are cases where we need to add dependencies BitBake is not able to find.
You can accomplish this by using a line like the following:
</p><pre class="literallayout">
PACKAGE_ARCHS[vardeps] = "MACHINE"
</pre><p>
This example explicitly adds the <code class="filename">MACHINE</code> variable as a
dependency for <code class="filename">PACKAGE_ARCHS</code>.
</p><p>
Consider a case with inline python, for example, where BitBake is not
able to figure out dependencies.
When running in debug mode (i.e. using <code class="filename">-DDD</code>), BitBake
produces output when it discovers something for which it cannot figure out
dependencies.
The Yocto Project team has currently not managed to cover those dependencies
in detail and is aware of the need to fix this situation.
</p><p>
Thus far, this section has limited discussion to the direct inputs into a task.
Information based on direct inputs is referred to as the "basehash" in the
code.
However, there is still the question of a task's indirect inputs - the
things that were already built and present in the build directory.
The checksum (or signature) for a particular task needs to add the hashes
of all the tasks on which the particular task depends.
Choosing which dependencies to add is a policy decision.
However, the effect is to generate a master checksum that combines the basehash
and the hashes of the task's dependencies.
</p><p>
At the code level, there are a variety of ways both the basehash and the
dependent task hashes can be influenced.
Within the BitBake configuration file, we can give BitBake some extra information
to help it construct the basehash.
The following statements effectively result in a list of global variable
dependency excludes - variables never included in any checksum:
</p><pre class="literallayout">
BB_HASHBASE_WHITELIST ?= "TMPDIR FILE PATH PWD BB_TASKHASH BBPATH"
BB_HASHBASE_WHITELIST += "DL_DIR SSTATE_DIR THISDIR FILESEXTRAPATHS"
BB_HASHBASE_WHITELIST += "FILE_DIRNAME HOME LOGNAME SHELL TERM USER"
BB_HASHBASE_WHITELIST += "FILESPATH USERNAME STAGING_DIR_HOST STAGING_DIR_TARGET"
</pre><p>
The previous example actually excludes
<a class="link" href="#var-WORKDIR" title="WORKDIR"><code class="filename">WORKDIR</code></a>
since it is actually constructed as a path within
<a class="link" href="#var-TMPDIR" title="TMPDIR"><code class="filename">TMPDIR</code></a>, which is on
the whitelist.
</p><p>
The rules for deciding which hashes of dependent tasks to include through
dependency chains are more complex and are generally accomplished with a
python function.
The code in <code class="filename">meta/lib/oe/sstatesig.py</code> shows two examples
of this and also illustrates how you can insert your own policy into the system
if so desired.
This file defines the two basic signature generators <code class="filename">OE-Core</code>
uses: "OEBasic" and "OEBasicHash".
By default, there is a dummy "noop" signature handler enabled in BitBake.
This means that behavior is unchanged from previous versions.
<code class="filename">OE-Core</code> uses the "OEBasic" signature handler by default
through this setting in the <code class="filename">bitbake.conf</code> file:
</p><pre class="literallayout">
BB_SIGNATURE_HANDLER ?= "OEBasic"
</pre><p>
The "OEBasicHash" <code class="filename">BB_SIGNATURE_HANDLER</code> is the same as the
"OEBasic" version but adds the task hash to the stamp files.
This results in any metadata change that changes the task hash, automatically
causing the task to be run again.
This removes the need to bump <a class="link" href="#var-PR" title="PR"><code class="filename">PR</code></a>
values and changes to metadata automatically ripple across the build.
Currently, this behavior is not the default behavior for <code class="filename">OE-Core</code>
but is the default in <code class="filename">poky</code>.
</p><p>
It is also worth noting that the end result of these signature generators is to
make some dependency and hash information available to the build.
This information includes:
</p><pre class="literallayout">
BB_BASEHASH_task-&lt;taskname&gt; - the base hashes for each task in the recipe
BB_BASEHASH_&lt;filename:taskname&gt; - the base hashes for each dependent task
BBHASHDEPS_&lt;filename:taskname&gt; - The task dependencies for each task
BB_TASKHASH - the hash of the currently running task
</pre><p>
</p></div><div class="section" title="3.2.3. Shared State"><div class="titlepage"><div><div><h3 class="title"><a id="shared-state"></a>3.2.3. Shared State</h3></div></div></div><p>
Checksums and dependencies, as discussed in the previous section, solve half the
problem.
The other part of the problem is being able to use checksum information during the build
and being able to reuse or rebuild specific components.
</p><p>
The shared state class (<code class="filename">sstate.bbclass</code>)
is a relatively generic implementation of how to "capture" a snapshot of a given task.
The idea is that the build process does not care about the source of a task's output.
Output could be freshly built or it could be downloaded and unpacked from
somewhere - the build process doesn't need to worry about its source.
</p><p>
There are two types of output, one is just about creating a directory
in <code class="filename">WORKDIR</code>.
A good example is the output of either <code class="filename">do_install</code> or
<code class="filename">do_package</code>.
The other type of output occurs when a set of data is merged into a shared directory
tree such as the sysroot.
</p><p>
The Yocto Project team has tried to keep the details of the implementation hidden in
<code class="filename">sstate.bbclass</code>.
From a user's perspective, adding shared state wrapping to a task
is as simple as this <code class="filename">do_deploy</code> example taken from
<code class="filename">do_deploy.bbclass</code>:
</p><pre class="literallayout">
DEPLOYDIR = "${WORKDIR}/deploy-${PN}"
SSTATETASKS += "do_deploy"
do_deploy[sstate-name] = "deploy"
do_deploy[sstate-inputdirs] = "${DEPLOYDIR}"
do_deploy[sstate-outputdirs] = "${DEPLOY_DIR_IMAGE}"
python do_deploy_setscene () {
sstate_setscene(d)
}
addtask do_deploy_setscene
</pre><p>
In the example, we add some extra flags to the task, a name field ("deploy"), an
input directory where the task sends data, and the output
directory where the data from the task should eventually be copied.
We also add a <code class="filename">_setscene</code> variant of the task and add the task
name to the <code class="filename">SSTATETASKS</code> list.
</p><p>
If you have a directory whose contents you need to preserve, you can do this with
a line like the following:
</p><pre class="literallayout">
do_package[sstate-plaindirs] = "${PKGD} ${PKGDEST}"
</pre><p>
This method, as well as the following example, also works for multiple directories.
</p><pre class="literallayout">
do_package[sstate-inputdirs] = "${PKGDESTWORK} ${SHLIBSWORKDIR}"
do_package[sstate-outputdirs] = "${PKGDATA_DIR} ${SHLIBSDIR}"
do_package[sstate-lockfile] = "${PACKAGELOCK}"
</pre><p>
These methods also include the ability to take a lockfile when manipulating
shared state directory structures since some cases are sensitive to file
additions or removals.
</p><p>
Behind the scenes, the shared state code works by looking in
<code class="filename">SSTATE_DIR</code> and
<code class="filename">SSTATE_MIRRORS</code> for shared state files.
Here is an example:
</p><pre class="literallayout">
SSTATE_MIRRORS ?= "\
file://.* http://someserver.tld/share/sstate/ \n \
file://.* file:///some/local/dir/sstate/"
</pre><p>
</p><p>
The shared state package validity can be detected just by looking at the
filename since the filename contains the task checksum (or signature) as
described earlier in this section.
If a valid shared state package is found, the build process downloads it
and uses it to accelerate the task.
</p><p>
The build processes uses the <code class="filename">*_setscene</code> tasks
for the task acceleration phase.
BitBake goes through this phase before the main execution code and tries
to accelerate any tasks for which it can find shared state packages.
If a shared state package for a task is available, the shared state
package is used.
This means the task and any tasks on which it is dependent are not
executed.
</p><p>
As a real world example, the aim is when building an IPK-based image,
only the <code class="filename">do_package_write_ipk</code> tasks would have their
shared state packages fetched and extracted.
Since the sysroot is not used, it would never get extracted.
This is another reason why a task-based approach is preferred over a
recipe-based approach, which would have to install the output from every task.
</p></div><div class="section" title="3.2.4. Tips and Tricks"><div class="titlepage"><div><div><h3 class="title"><a id="tips-and-tricks"></a>3.2.4. Tips and Tricks</h3></div></div></div><p>
The code in the build system that supports incremental builds is not
simple code.
This section presents some tips and tricks that help you work around
issues related to shared state code.
</p><div class="section" title="3.2.4.1. Debugging"><div class="titlepage"><div><div><h4 class="title"><a id="debugging"></a>3.2.4.1. Debugging</h4></div></div></div><p>
When things go wrong, debugging needs to be straightforward.
Because of this, the Yocto Project team included strong debugging
tools:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Whenever a shared state package is written out, so is a
corresponding <code class="filename">.siginfo</code> file.
This practice results in a pickled python database of all
the metadata that went into creating the hash for a given shared state
package.</p></li><li class="listitem"><p>If BitBake is run with the <code class="filename">--dump-signatures</code>
(or <code class="filename">-S</code>) option, BitBake dumps out
<code class="filename">.siginfo</code> files in
the stamp directory for every task it would have executed instead of
building the specified target package.</p></li><li class="listitem"><p>There is a <code class="filename">bitbake-diffsigs</code> command that
can process these <code class="filename">.siginfo</code> files.
If one file is specified, it will dump out the dependency
information in the file.
If two files are specified, it will compare the two files and dump out
the differences between the two.
This allows the question of "What changed between X and Y?" to be
answered easily.</p></li></ul></div><p>
</p></div><div class="section" title="3.2.4.2. Invalidating Shared State"><div class="titlepage"><div><div><h4 class="title"><a id="invalidating-shared-state"></a>3.2.4.2. Invalidating Shared State</h4></div></div></div><p>
The shared state code uses checksums and shared state
cache to avoid unnecessarily rebuilding tasks.
As with all schemes, this one has some drawbacks.
It is possible that you could make implicit changes that are not factored
into the checksum calculation, but do affect a task's output.
A good example is perhaps when a tool changes its output.
Let's say that the output of <code class="filename">rpmdeps</code> needed to change.
The result of the change should be that all the "package", "package_write_rpm",
and "package_deploy-rpm" shared state cache items would become invalid.
But, because this is a change that is external to the code and therefore implicit,
the associated shared state cache items do not become invalidated.
In this case, the build process would use the cached items rather than running the
task again.
Obviously, these types of implicit changes can cause problems.
</p><p>
To avoid these problems during the build, you need to understand the effects of any
change you make.
Note that any changes you make directly to a function automatically are factored into
the checksum calculation and thus, will invalidate the associated area of sstate cache.
You need to be aware of any implicit changes that are not obvious changes to the
code and could affect the output of a given task.
Once you are aware of such a change, you can take steps to invalidate the cache
and force the task to run.
The step to take is as simple as changing a function's comments in the source code.
For example, to invalidate package shared state files, change the comment statements
of <code class="filename">do_package</code> or the comments of one of the functions it calls.
The change is purely cosmetic, but it causes the checksum to be recalculated and
forces the task to be run again.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
For an example of a commit that makes a cosmetic change to invalidate
a shared state, see this
<a class="ulink" href="http://git.yoctoproject.org/cgit.cgi/poky/commit/meta/classes/package.bbclass?id=737f8bbb4f27b4837047cb9b4fbfe01dfde36d54" target="_top">commit</a>.
</div></div></div></div><div class="section" title="3.3. x32"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="x32"></a>3.3. x32</h2></div></div></div><p>
x32 is a new processor-specific Application Binary Interface (psABI) for x86_64.
An ABI defines the calling conventions between functions in a processing environment.
The interface determines what registers are used and what the sizes are for various C data types.
</p><p>
Some processing environments prefer using 32-bit applications even when running
on Intel 64-bit platforms.
Consider the i386 psABI, which is a very old 32-bit ABI for Intel 64-bit platforms.
The i386 psABI does not provide efficient use and access of the Intel 64-bit processor resources,
leaving the system underutilized.
Now consider the x86_64 psABI.
This ABI is newer and uses 64-bits for data sizes and program pointers.
The extra bits increase the footprint size of the programs, libraries,
and also increases the memory and file system size requirements.
Executing under the x32 psABI enables user programs to utilize CPU and system resources
more efficiently while keeping the memory footprint of the applications low.
Extra bits are used for registers but not for addressing mechanisms.
</p><div class="section" title="3.3.1. Support"><div class="titlepage"><div><div><h3 class="title"><a id="support"></a>3.3.1. Support</h3></div></div></div><p>
While the x32 psABI specifications are not fully finalized, this Yocto Project
release supports current development specifications of x32 psABI.
As of this release of the Yocto Project, x32 psABI support exists as follows:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>You can create packages and images in x32 psABI format on x86_64 architecture targets.
</p></li><li class="listitem"><p>You can use the x32 psABI support through the <code class="filename">meta-x32</code>
layer on top of the OE-core/Yocto layer.</p></li><li class="listitem"><p>The toolchain from the <code class="filename">experimental/meta-x32</code> layer
is used for building x32 psABI program binaries.</p></li><li class="listitem"><p>You can successfully build many recipes with the x32 toolchain.</p></li><li class="listitem"><p>You can create and boot <code class="filename">core-image-minimal</code> and
<code class="filename">core-image-sato</code> images.</p></li></ul></div><p>
</p></div><div class="section" title="3.3.2. Future Development and Limitations"><div class="titlepage"><div><div><h3 class="title"><a id="future-development-and-limitations"></a>3.3.2. Future Development and Limitations</h3></div></div></div><p>
As of this Yocto Project release, the x32 psABI kernel and library interfaces
specifications are not finalized.
</p><p>
Future Plans for the x32 psABI in the Yocto Project include the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Enhance and fix the few remaining recipes so they
work with and support x32 toolchains.</p></li><li class="listitem"><p>Enhance RPM Package Manager (RPM) support for x32 binaries.</p></li><li class="listitem"><p>Support larger images.</p></li><li class="listitem"><p>Integrate x32 recipes, toolchain, and kernel changes from
<code class="filename">experimental/meta-x32</code> into OE-core.</p></li></ul></div><p>
</p></div><div class="section" title="3.3.3. Using x32 Right Now"><div class="titlepage"><div><div><h3 class="title"><a id="using-x32-right-now"></a>3.3.3. Using x32 Right Now</h3></div></div></div><p>
Despite the fact the x32 psABI support is in development state for this release of the
Yocto Project, you can follow these steps to use the x32 spABI:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Add the <code class="filename">experimental/meta-x32</code> layer to your local
<a class="link" href="#build-directory" target="_top">build directory</a>.
You can find the <code class="filename">experimental/meta-x32</code> source repository at
<a class="ulink" href="http://git.yoctoproject.org" target="_top">http://git.yoctoproject.org</a>.</p></li><li class="listitem"><p>Edit your <code class="filename">conf/bblayers.conf</code> file so that it includes
the <code class="filename">meta-x32</code>.
Here is an example:
</p><pre class="literallayout">
BBLAYERS ?= " \
/home/nitin/prj/poky.git/meta \
/home/nitin/prj/poky.git/meta-yocto \
/home/nitin/prj/meta-x32.git \
"
</pre></li><li class="listitem"><p>Enable the x32 psABI tuning file for <code class="filename">x86_64</code>
machines by editing the <code class="filename">conf/local.conf</code> like this:
</p><pre class="literallayout">
MACHINE = "qemux86-64"
DEFAULTTUNE = "x86-64-x32"
baselib = "${@d.getVar('BASE_LIB_tune-' + (d.getVar('DEFAULTTUNE', True) \
or 'INVALID'), True) or 'lib'}"
#MACHINE = "atom-pc"
#DEFAULTTUNE = "core2-64-x32"
</pre></li><li class="listitem"><p>As usual, use BitBake to build an image that supports the x32 psABI.
Here is an example:
</p><pre class="literallayout">
$ bitake core-image-sato
</pre></li><li class="listitem"><p>As usual, run your image using QEMU:
</p><pre class="literallayout">
$ runqemu qemux86-64 core-image-sato
</pre></li></ul></div><p>
</p></div></div><div class="section" title="3.4. Licenses"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="licenses"></a>3.4. Licenses</h2></div></div></div><p>
This section describes the mechanism by which the OpenEmbedded build system
tracks changes to licensing text.
The section also describes how to enable commercially licensed recipes,
which by default are disabled.
</p><div class="section" title="3.4.1. Tracking License Changes"><div class="titlepage"><div><div><h3 class="title"><a id="usingpoky-configuring-LIC_FILES_CHKSUM"></a>3.4.1. Tracking License Changes</h3></div></div></div><p>
The license of an upstream project might change in the future.
In order to prevent these changes going unnoticed, the
<code class="filename"><a class="link" href="#var-LIC_FILES_CHKSUM" title="LIC_FILES_CHKSUM">LIC_FILES_CHKSUM</a></code>
variable tracks changes to the license text. The checksums are validated at the end of the
configure step, and if the checksums do not match, the build will fail.
</p><div class="section" title="3.4.1.1. Specifying the LIC_FILES_CHKSUM Variable"><div class="titlepage"><div><div><h4 class="title"><a id="usingpoky-specifying-LIC_FILES_CHKSUM"></a>3.4.1.1. Specifying the <code class="filename">LIC_FILES_CHKSUM</code> Variable</h4></div></div></div><p>
The <code class="filename">LIC_FILES_CHKSUM</code>
variable contains checksums of the license text in the source code for the recipe.
Following is an example of how to specify <code class="filename">LIC_FILES_CHKSUM</code>:
</p><pre class="literallayout">
LIC_FILES_CHKSUM = "file://COPYING;md5=xxxx \
file://licfile1.txt;beginline=5;endline=29;md5=yyyy \
file://licfile2.txt;endline=50;md5=zzzz \
..."
</pre><p>
</p><p>
The build system uses the
<code class="filename"><a class="link" href="#var-S" title="S">S</a></code> variable as the
default directory used when searching files listed in
<code class="filename">LIC_FILES_CHKSUM</code>.
The previous example employs the default directory.
</p><p>
You can also use relative paths as shown in the following example:
</p><pre class="literallayout">
LIC_FILES_CHKSUM = "file://src/ls.c;startline=5;endline=16;\
md5=bb14ed3c4cda583abc85401304b5cd4e"
LIC_FILES_CHKSUM = "file://../license.html;md5=5c94767cedb5d6987c902ac850ded2c6"
</pre><p>
</p><p>
In this example, the first line locates a file in
<code class="filename">${S}/src/ls.c</code>.
The second line refers to a file in
<code class="filename"><a class="link" href="#var-WORKDIR" title="WORKDIR">WORKDIR</a></code>, which is the parent
of <code class="filename"><a class="link" href="#var-S" title="S">S</a></code>.
</p><p>
Note that this variable is mandatory for all recipes, unless the
<code class="filename">LICENSE</code> variable is set to "CLOSED".
</p></div><div class="section" title="3.4.1.2. Explanation of Syntax"><div class="titlepage"><div><div><h4 class="title"><a id="usingpoky-LIC_FILES_CHKSUM-explanation-of-syntax"></a>3.4.1.2. Explanation of Syntax</h4></div></div></div><p>
As mentioned in the previous section, the
<code class="filename">LIC_FILES_CHKSUM</code> variable lists all the
important files that contain the license text for the source code.
It is possible to specify a checksum for an entire file, or a specific section of a
file (specified by beginning and ending line numbers with the "beginline" and "endline"
parameters, respectively).
The latter is useful for source files with a license notice header,
README documents, and so forth.
If you do not use the "beginline" parameter, then it is assumed that the text begins on the
first line of the file.
Similarly, if you do not use the "endline" parameter, it is assumed that the license text
ends with the last line of the file.
</p><p>
The "md5" parameter stores the md5 checksum of the license text.
If the license text changes in any way as compared to this parameter
then a mismatch occurs.
This mismatch triggers a build failure and notifies the developer.
Notification allows the developer to review and address the license text changes.
Also note that if a mismatch occurs during the build, the correct md5
checksum is placed in the build log and can be easily copied to the recipe.
</p><p>
There is no limit to how many files you can specify using the
<code class="filename">LIC_FILES_CHKSUM</code> variable.
Generally, however, every project requires a few specifications for license tracking.
Many projects have a "COPYING" file that stores the license information for all the source
code files.
This practice allows you to just track the "COPYING" file as long as it is kept up to date.
</p><div class="tip" title="Tip" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Tip</h3>
If you specify an empty or invalid "md5" parameter, BitBake returns an md5 mis-match
error and displays the correct "md5" parameter value during the build.
The correct parameter is also captured in the build log.
</div><div class="tip" title="Tip" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Tip</h3>
If the whole file contains only license text, you do not need to use the "beginline" and
"endline" parameters.
</div></div></div><div class="section" title="3.4.2. Enabling Commercially Licensed Recipes"><div class="titlepage"><div><div><h3 class="title"><a id="enabling-commercially-licensed-recipes"></a>3.4.2. Enabling Commercially Licensed Recipes</h3></div></div></div><p>
By default, the OpenEmbedded build system disables
components that have commercial or other special licensing
requirements.
Such requirements are defined on a
recipe-by-recipe basis through the <code class="filename">LICENSE_FLAGS</code> variable
definition in the affected recipe.
For instance, the
<code class="filename">$HOME/poky/meta/recipes-multimedia/gstreamer/gst-plugins-ugly</code>
recipe contains the following statement:
</p><pre class="literallayout">
LICENSE_FLAGS = "commercial"
</pre><p>
Here is a slightly more complicated example that contains both an
explicit package name and version (after variable expansion):
</p><pre class="literallayout">
LICENSE_FLAGS = "license_${PN}_${PV}"
</pre><p>
In order for a component restricted by a <code class="filename">LICENSE_FLAGS</code>
definition to be enabled and included in an image, it
needs to have a matching entry in the global
<code class="filename">LICENSE_FLAGS_WHITELIST</code> variable, which is a variable
typically defined in your <code class="filename">local.conf</code> file.
For example, to enable
the <code class="filename">$HOME/poky/meta/recipes-multimedia/gstreamer/gst-plugins-ugly</code>
package, you could add either the string
"commercial_gst-plugins-ugly" or the more general string
"commercial" to <code class="filename">LICENSE_FLAGS_WHITELIST</code>.
See the
"<a class="link" href="#license-flag-matching" title="3.4.2.1. License Flag Matching">License Flag Matching</a>" section
for a full explanation of how <code class="filename">LICENSE_FLAGS</code> matching works.
Here is the example:
</p><pre class="literallayout">
LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly"
</pre><p>
Likewise, to additionally enable the package containing
<code class="filename">LICENSE_FLAGS = "license_${PN}_${PV}"</code>, and assuming
that the actual recipe name was <code class="filename">emgd_1.10.bb</code>,
the following string would enable that package as well as
the original <code class="filename">gst-plugins-ugly</code> package:
</p><pre class="literallayout">
LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly license_emgd_1.10"
</pre><p>
As a convenience, you do not need to specify the complete license string
in the whitelist for every package.
you can use an abbreviated form, which consists
of just the first portion or portions of the license string before
the initial underscore character or characters.
A partial string will match
any license that contains the given string as the first
portion of its license.
For example, the following
whitelist string will also match both of the packages
previously mentioned as well as any other packages that have
licenses starting with "commercial" or "license".
</p><pre class="literallayout">
LICENSE_FLAGS_WHITELIST = "commercial license"
</pre><p>
</p><div class="section" title="3.4.2.1. License Flag Matching"><div class="titlepage"><div><div><h4 class="title"><a id="license-flag-matching"></a>3.4.2.1. License Flag Matching</h4></div></div></div><p>
The definition of 'matching' in reference to a
recipe's <code class="filename">LICENSE_FLAGS</code> setting is simple.
However, some things exist that you should know about in order to
correctly and effectively use it.
</p><p>
Before a flag
defined by a particular recipe is tested against the
contents of the <code class="filename">LICENSE_FLAGS_WHITELIST</code> variable, the
string <code class="filename">_${PN}</code> (with
<a class="link" href="#var-PN" title="PN"><code class="filename">PN</code></a> expanded of course) is
appended to the flag, thus automatically making each
<code class="filename">LICENSE_FLAGS</code> value recipe-specific.
That string is
then matched against the whitelist.
So if you specify <code class="filename">LICENSE_FLAGS = "commercial"</code> in recipe
"foo" for example, the string <code class="filename">"commercial_foo"</code>
would normally be what is specified in the whitelist in order for it to
match.
</p><p>
You can broaden the match by
putting any "_"-separated beginning subset of a
<code class="filename">LICENSE_FLAGS</code> flag in the whitelist, which will also
match.
For example, simply specifying "commercial" in
the whitelist would match any expanded <code class="filename">LICENSE_FLAGS</code>
definition starting with "commercial" such as
"commercial_foo" and "commercial_bar", which are the
strings that would be automatically generated for
hypothetical "foo" and "bar" recipes assuming those
recipes had simply specified the following:
</p><pre class="literallayout">
LICENSE_FLAGS = "commercial"
</pre><p>
</p><p>
Broadening the match allows for a range of specificity for the items
in the whitelist, from more general to perfectly
specific.
So you have the choice of exhaustively
enumerating each license flag in the whitelist to
allow only those specific recipes into the image, or
of using a more general string to pick up anything
matching just the first component or components of the specified
string.
</p><p>
This scheme works even if the flag already
has <code class="filename">_${PN}</code> appended - the extra <code class="filename">_${PN}</code> is
redundant, but does not affect the outcome.
For example, a license flag of "commercial_1.2_foo" would
turn into "commercial_1.2_foo_foo" and would match
both the general "commercial" and the specific
"commercial_1.2_foo", as expected.
The flag would also match
"commercial_1.2_foo_foo" and "commercial_1.2", which
does not make much sense regarding use in the whitelist.
</p><p>
For a versioned string, you could instead specify
"commercial_foo_1.2", which would turn into
"commercial_foo_1.2_foo".
And, as expected, this flag allows
you to pick up this package along with
anything else "commercial" when you specify "commercial"
in the whitelist.
Or, the flag allows you to pick up this package along with anything "commercial_foo"
regardless of version when you use "commercial_foo" in the whitelist.
Finally, you can be completely specific about the package and version and specify
"commercial_foo_1.2" package and version.
</p></div><div class="section" title="3.4.2.2. Other Variables Related to Commercial Licenses"><div class="titlepage"><div><div><h4 class="title"><a id="other-variables-related-to-commercial-licenses"></a>3.4.2.2. Other Variables Related to Commercial Licenses</h4></div></div></div><p>
Other helpful variables related to commercial
license handling exist and are defined in the
<code class="filename">$HOME/poky/meta/conf/distro/include/default-distrovars.inc</code> file:
</p><pre class="literallayout">
COMMERCIAL_AUDIO_PLUGINS ?= ""
COMMERCIAL_VIDEO_PLUGINS ?= ""
COMMERCIAL_QT = ""
</pre><p>
If you want to enable these components, you can do so by making sure you have
the following statements in your <code class="filename">local.conf</code> configuration file:
</p><pre class="literallayout">
COMMERCIAL_AUDIO_PLUGINS = "gst-plugins-ugly-mad \
gst-plugins-ugly-mpegaudioparse"
COMMERCIAL_VIDEO_PLUGINS = "gst-plugins-ugly-mpeg2dec \
gst-plugins-ugly-mpegstream gst-plugins-bad-mpegvideoparse"
COMMERCIAL_QT ?= "qmmp"
LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly commercial_gst-plugins-bad commercial_qmmp"
</pre><p>
Of course, you could also create a matching whitelist
for those components using the more general "commercial"
in the whitelist, but that would also enable all the
other packages with <code class="filename">LICENSE_FLAGS</code> containing
"commercial", which you may or may not want:
</p><pre class="literallayout">
LICENSE_FLAGS_WHITELIST = "commercial"
</pre><p>
</p><p>
Specifying audio and video plug-ins as part of the
<code class="filename">COMMERCIAL_AUDIO_PLUGINS</code> and
<code class="filename">COMMERCIAL_VIDEO_PLUGINS</code> statements
or commercial qt components as part of
the <code class="filename">COMMERCIAL_QT</code> statement (along
with the enabling <code class="filename">LICENSE_FLAGS_WHITELIST</code>) includes the
plug-ins or components into built images, thus adding
support for media formats or components.
</p></div></div></div></div>
<div class="chapter" title="Chapter 4. Source Directory Structure"><div class="titlepage"><div><div><h2 class="title"><a id="ref-structure"></a>Chapter 4. Source Directory Structure</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#structure-core">4.1. Top level core components</a></span></dt><dd><dl><dt><span class="section"><a href="#structure-core-bitbake">4.1.1. <code class="filename">bitbake/</code></a></span></dt><dt><span class="section"><a href="#structure-core-build">4.1.2. <code class="filename">build/</code></a></span></dt><dt><span class="section"><a href="#handbook">4.1.3. <code class="filename">documentation</code></a></span></dt><dt><span class="section"><a href="#structure-core-meta">4.1.4. <code class="filename">meta/</code></a></span></dt><dt><span class="section"><a href="#structure-core-meta-demoapps">4.1.5. <code class="filename">meta-demoapps/</code></a></span></dt><dt><span class="section"><a href="#structure-core-meta-rt">4.1.6. <code class="filename">meta-rt/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-skeleton">4.1.7. <code class="filename">meta-skeleton/</code></a></span></dt><dt><span class="section"><a href="#structure-core-scripts">4.1.8. <code class="filename">scripts/</code></a></span></dt><dt><span class="section"><a href="#structure-core-script">4.1.9. <code class="filename">oe-init-build-env</code></a></span></dt><dt><span class="section"><a href="#structure-basic-top-level">4.1.10. <code class="filename">LICENSE, README, and README.hardware</code></a></span></dt></dl></dd><dt><span class="section"><a href="#structure-build">4.2. The Build Directory - <code class="filename">build/</code></a></span></dt><dd><dl><dt><span class="section"><a href="#structure-build-pseudodone">4.2.1. <code class="filename">build/pseudodone</code></a></span></dt><dt><span class="section"><a href="#structure-build-conf-local.conf">4.2.2. <code class="filename">build/conf/local.conf</code></a></span></dt><dt><span class="section"><a href="#structure-build-conf-bblayers.conf">4.2.3. <code class="filename">build/conf/bblayers.conf</code></a></span></dt><dt><span class="section"><a href="#structure-build-conf-sanity_info">4.2.4. <code class="filename">build/conf/sanity_info</code></a></span></dt><dt><span class="section"><a href="#structure-build-downloads">4.2.5. <code class="filename">build/downloads/</code></a></span></dt><dt><span class="section"><a href="#structure-build-sstate-cache">4.2.6. <code class="filename">build/sstate-cache/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp">4.2.7. <code class="filename">build/tmp/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-buildstats">4.2.8. <code class="filename">build/tmp/buildstats/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-cache">4.2.9. <code class="filename">build/tmp/cache/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy">4.2.10. <code class="filename">build/tmp/deploy/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy-deb">4.2.11. <code class="filename">build/tmp/deploy/deb/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy-rpm">4.2.12. <code class="filename">build/tmp/deploy/rpm/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy-licenses">4.2.13. <code class="filename">build/tmp/deploy/licenses/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy-images">4.2.14. <code class="filename">build/tmp/deploy/images/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-deploy-ipk">4.2.15. <code class="filename">build/tmp/deploy/ipk/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-sysroots">4.2.16. <code class="filename">build/tmp/sysroots/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-stamps">4.2.17. <code class="filename">build/tmp/stamps/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-log">4.2.18. <code class="filename">build/tmp/log/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-pkgdata">4.2.19. <code class="filename">build/tmp/pkgdata/</code></a></span></dt><dt><span class="section"><a href="#structure-build-tmp-work">4.2.20. <code class="filename">build/tmp/work/</code></a></span></dt></dl></dd><dt><span class="section"><a href="#structure-meta">4.3. The Metadata - <code class="filename">meta/</code></a></span></dt><dd><dl><dt><span class="section"><a href="#structure-meta-classes">4.3.1. <code class="filename">meta/classes/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-conf">4.3.2. <code class="filename">meta/conf/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-conf-machine">4.3.3. <code class="filename">meta/conf/machine/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-conf-distro">4.3.4. <code class="filename">meta/conf/distro/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-bsp">4.3.5. <code class="filename">meta/recipes-bsp/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-connectivity">4.3.6. <code class="filename">meta/recipes-connectivity/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-core">4.3.7. <code class="filename">meta/recipes-core/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-devtools">4.3.8. <code class="filename">meta/recipes-devtools/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-extended">4.3.9. <code class="filename">meta/recipes-extended/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-gnome">4.3.10. <code class="filename">meta/recipes-gnome/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-graphics">4.3.11. <code class="filename">meta/recipes-graphics/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-kernel">4.3.12. <code class="filename">meta/recipes-kernel/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-multimedia">4.3.13. <code class="filename">meta/recipes-multimedia/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-qt">4.3.14. <code class="filename">meta/recipes-qt/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-rt">4.3.15. <code class="filename">meta/recipes-rt/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-sato">4.3.16. <code class="filename">meta/recipes-sato/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-support">4.3.17. <code class="filename">meta/recipes-support/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-site">4.3.18. <code class="filename">meta/site/</code></a></span></dt><dt><span class="section"><a href="#structure-meta-recipes-txt">4.3.19. <code class="filename">meta/recipes.txt</code></a></span></dt></dl></dd></dl></div><p>
The <a class="link" href="#source-directory" target="_top">source directory</a> consists of several components.
Understanding them and knowing where they are located is key to using the Yocto Project well.
This chapter describes the source directory and gives information about the various
files and directories.
</p><p>
For information on how to establish a local source directory on your development system, see the
"<a class="link" href="#getting-setup" target="_top">Getting Set Up</a>"
section in the Yocto Project Development Manual.
</p><div class="section" title="4.1. Top level core components"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="structure-core"></a>4.1. Top level core components</h2></div></div></div><div class="section" title="4.1.1. bitbake/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-core-bitbake"></a>4.1.1. <code class="filename">bitbake/</code></h3></div></div></div><p>
The <a class="ulink" href="source-directory" target="_top">source directory</a>
includes a copy of BitBake for ease of use.
The copy usually matches the current stable BitBake release from the BitBake project.
BitBake, a metadata interpreter, reads the Yocto Project metadata and runs the tasks
defined by that data.
Failures are usually from the metadata and not from BitBake itself.
Consequently, most users do not need to worry about BitBake.
</p><p>
When you run the <code class="filename">bitbake</code> command, the wrapper script in
<code class="filename">scripts/</code> is executed to run the main BitBake executable,
which resides in the <code class="filename">bitbake/bin/</code> directory.
Sourcing the <a class="link" href="#structure-core-script" title="4.1.9. oe-init-build-env">oe-init-build-env</a>
script places the <code class="filename">scripts</code> and <code class="filename">bitbake/bin</code>
directories (in that order) into the shell's <code class="filename">PATH</code> environment
variable.
</p><p>
For more information on BitBake, see the BitBake on-line manual at
<a class="ulink" href="http://docs.openembedded.org/bitbake/html/" target="_top">http://docs.openembedded.org/bitbake/html/</a>.
</p></div><div class="section" title="4.1.2. build/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-core-build"></a>4.1.2. <code class="filename">build/</code></h3></div></div></div><p>
This directory contains user configuration files and the output
generated by the OpenEmbedded build system in its standard configuration where
the source tree is combined with the output.
The <a class="link" href="#build-directory" target="_top">build directory</a>
is created initially when you <code class="filename">source</code>
the OpenEmbedded build environment setup script <code class="filename">oe-init-build-env</code>.
</p><p>
It is also possible to place output and configuration
files in a directory separate from the
<a class="link" href="#source-directory" target="_top">source directory</a>
by providing a directory name when you <code class="filename">source</code>
the setup script.
For information on separating output from your local source directory files, see <a class="link" href="#structure-core-script" title="4.1.9. oe-init-build-env">oe-init-build-env</a>.
</p></div><div class="section" title="4.1.3. documentation"><div class="titlepage"><div><div><h3 class="title"><a id="handbook"></a>4.1.3. <code class="filename">documentation</code></h3></div></div></div><p>
This directory holds the source for the Yocto Project documentation
as well as templates and tools that allow you to generate PDF and HTML
versions of the manuals.
Each manual is contained in a sub-folder.
For example, the files for this manual reside in
<code class="filename">poky-ref-manual</code>.
</p></div><div class="section" title="4.1.4. meta/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-core-meta"></a>4.1.4. <code class="filename">meta/</code></h3></div></div></div><p>
This directory contains the OpenEmbedded Core metadata.
The directory holds machine definitions, the Yocto Project distribution,
and the packages that make up a given system.
</p></div><div class="section" title="4.1.5. meta-demoapps/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-core-meta-demoapps"></a>4.1.5. <code class="filename">meta-demoapps/</code></h3></div></div></div><p>
This directory contains recipes for applications and demos that are not part of the
OpenEmbedded core.
</p></div><div class="section" title="4.1.6. meta-rt/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-core-meta-rt"></a>4.1.6. <code class="filename">meta-rt/</code></h3></div></div></div><p>
This directory contains recipes for real-time kernels.
</p></div><div class="section" title="4.1.7. meta-skeleton/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-skeleton"></a>4.1.7. <code class="filename">meta-skeleton/</code></h3></div></div></div><p>
This directory contains template recipes for BSP and kernel development.
</p></div><div class="section" title="4.1.8. scripts/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-core-scripts"></a>4.1.8. <code class="filename">scripts/</code></h3></div></div></div><p>
This directory contains various integration scripts that implement
extra functionality in the Yocto Project environment (e.g. QEMU scripts).
The <a class="link" href="#structure-core-script" title="4.1.9. oe-init-build-env">oe-init-build-env</a> script appends this
directory to the shell's <code class="filename">PATH</code> environment variable.
</p><p>
The <code class="filename">scripts</code> directory has useful scripts that assist contributing
back to the Yocto Project, such as <code class="filename">create_pull_request</code> and
<code class="filename">send_pull_request</code>.
</p></div><div class="section" title="4.1.9. oe-init-build-env"><div class="titlepage"><div><div><h3 class="title"><a id="structure-core-script"></a>4.1.9. <code class="filename">oe-init-build-env</code></h3></div></div></div><p>
This script sets up the OpenEmbedded build environment.
Running this script with the <code class="filename">source</code> command in
a shell makes changes to <code class="filename">PATH</code> and sets other core BitBake variables based on the
current working directory.
You need to run this script before running BitBake commands.
The script uses other scripts within the <code class="filename">scripts</code> directory to do
the bulk of the work.
</p><p>
By default, running this script without a build directory argument creates the
<code class="filename">build</code> directory.
If you provide a build directory argument when you <code class="filename">source</code>
the script, you direct OpenEmbedded build system to create a
<a class="link" href="#build-directory" target="_top">build directory</a> of your choice.
For example, the following command creates a build directory named
<code class="filename">mybuilds</code> that is outside of the
<a class="link" href="#source-directory" target="_top">source directory</a>:
</p><pre class="literallayout">
$ source oe-init-build-env ~/mybuilds
</pre><p>
</p></div><div class="section" title="4.1.10. LICENSE, README, and README.hardware"><div class="titlepage"><div><div><h3 class="title"><a id="structure-basic-top-level"></a>4.1.10. <code class="filename">LICENSE, README, and README.hardware</code></h3></div></div></div><p>
These files are standard top-level files.
</p></div></div><div class="section" title="4.2. The Build Directory - build/"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="structure-build"></a>4.2. The Build Directory - <code class="filename">build/</code></h2></div></div></div><div class="section" title="4.2.1. build/pseudodone"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-pseudodone"></a>4.2.1. <code class="filename">build/pseudodone</code></h3></div></div></div><p>
This tag file indicates that the initial pseudo binary was created.
The file is built the first time BitBake is invoked.
</p></div><div class="section" title="4.2.2. build/conf/local.conf"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-conf-local.conf"></a>4.2.2. <code class="filename">build/conf/local.conf</code></h3></div></div></div><p>
This file contains all the local user configuration for your build environment.
If there is no <code class="filename">local.conf</code> present, it is created from
<code class="filename">local.conf.sample</code>.
The <code class="filename">local.conf</code> file contains documentation on the various configuration options.
Any variable set here overrides any variable set elsewhere within the environment unless
that variable is hard-coded within a file (e.g. by using '=' instead of '?=').
Some variables are hard-coded for various reasons but these variables are
relatively rare.
</p><p>
Edit this file to set the <code class="filename"><a class="link" href="#var-MACHINE" title="MACHINE">MACHINE</a></code>
for which you want to build, which package types you
wish to use (<code class="filename">PACKAGE_CLASSES</code>), or where you want to downloaded files
(<code class="filename"><a class="link" href="#var-DL_DIR" title="DL_DIR">DL_DIR</a></code>).
</p></div><div class="section" title="4.2.3. build/conf/bblayers.conf"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-conf-bblayers.conf"></a>4.2.3. <code class="filename">build/conf/bblayers.conf</code></h3></div></div></div><p>
This file defines layers, which is a directory tree, traversed (or walked) by BitBake.
If <code class="filename">bblayers.conf</code>
is not present, it is created from <code class="filename">bblayers.conf.sample</code> when
you <code class="filename">source</code> the environment setup script.
</p></div><div class="section" title="4.2.4. build/conf/sanity_info"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-conf-sanity_info"></a>4.2.4. <code class="filename">build/conf/sanity_info</code></h3></div></div></div><p>
This file is created during the build to indicate the state of the sanity checks.
</p></div><div class="section" title="4.2.5. build/downloads/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-downloads"></a>4.2.5. <code class="filename">build/downloads/</code></h3></div></div></div><p>
This directory is used for the upstream source tarballs.
The directory can be reused by multiple builds or moved to another location.
You can control the location of this directory through the
<code class="filename"><a class="link" href="#var-DL_DIR" title="DL_DIR">DL_DIR</a></code> variable.
</p></div><div class="section" title="4.2.6. build/sstate-cache/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-sstate-cache"></a>4.2.6. <code class="filename">build/sstate-cache/</code></h3></div></div></div><p>
This directory is used for the shared state cache.
The directory can be reused by multiple builds or moved to another location.
You can control the location of this directory through the
<code class="filename"><a class="link" href="#var-SSTATE_DIR" title="SSTATE_DIR">SSTATE_DIR</a></code> variable.
</p></div><div class="section" title="4.2.7. build/tmp/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp"></a>4.2.7. <code class="filename">build/tmp/</code></h3></div></div></div><p>
This directory receives all the OpenEmbedded build system's output.
BitBake creates this directory if it does not exist.
As a last resort, to clean up a build and start it from scratch (other than the downloads),
you can remove everything in the <code class="filename">tmp</code> directory or get rid of the
directory completely.
If you do, you should also completely remove the <code class="filename">build/sstate-cache</code>
directory as well.
</p></div><div class="section" title="4.2.8. build/tmp/buildstats/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-buildstats"></a>4.2.8. <code class="filename">build/tmp/buildstats/</code></h3></div></div></div><p>
This directory stores the build statistics.
</p></div><div class="section" title="4.2.9. build/tmp/cache/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-cache"></a>4.2.9. <code class="filename">build/tmp/cache/</code></h3></div></div></div><p>
When BitBake parses the metadata, it creates a cache file of the result that can
be used when subsequently running commands.
These results are stored here on a per-machine basis.
</p></div><div class="section" title="4.2.10. build/tmp/deploy/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-deploy"></a>4.2.10. <code class="filename">build/tmp/deploy/</code></h3></div></div></div><p>
This directory contains any 'end result' output from the OpenEmbedded build process.
</p></div><div class="section" title="4.2.11. build/tmp/deploy/deb/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-deploy-deb"></a>4.2.11. <code class="filename">build/tmp/deploy/deb/</code></h3></div></div></div><p>
This directory receives any <code class="filename">.deb</code> packages produced by
the build process.
The packages are sorted into feeds for different architecture types.
</p></div><div class="section" title="4.2.12. build/tmp/deploy/rpm/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-deploy-rpm"></a>4.2.12. <code class="filename">build/tmp/deploy/rpm/</code></h3></div></div></div><p>
This directory receives any <code class="filename">.rpm</code> packages produced by
the build process.
The packages are sorted into feeds for different architecture types.
</p></div><div class="section" title="4.2.13. build/tmp/deploy/licenses/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-deploy-licenses"></a>4.2.13. <code class="filename">build/tmp/deploy/licenses/</code></h3></div></div></div><p>
This directory receives package licensing information.
For example, the directory contains sub-directories for <code class="filename">bash</code>,
<code class="filename">busybox</code>, and <code class="filename">eglibc</code> (among others) that in turn
contain appropriate <code class="filename">COPYING</code> license files with other licensing information.
</p></div><div class="section" title="4.2.14. build/tmp/deploy/images/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-deploy-images"></a>4.2.14. <code class="filename">build/tmp/deploy/images/</code></h3></div></div></div><p>
This directory receives complete filesystem images.
If you want to flash the resulting image from a build onto a device, look here for the image.
</p><p>
Be careful when deleting files in this directory.
You can safely delete old images from this directory (e.g.
<code class="filename">core-image-*</code>, <code class="filename">hob-image-*</code>,
etc.).
However, the kernel (<code class="filename">*zImage*</code>, <code class="filename">*uImage*</code>, etc.),
bootloader and other supplementary files might be deployed here prior to building an
image.
Because these files, however, are not directly produced from the image, if you
delete them they will not be automatically re-created when you build the image again.
</p><p>
If you do accidentally delete files here, you will need to force them to be
re-created.
In order to do that, you will need to know the target that produced them.
For example, these commands rebuild and re-create the kernel files:
</p><pre class="literallayout">
$ bitbake -c clean virtual/kernel
$ bitbake virtual/kernel
</pre><p>
</p></div><div class="section" title="4.2.15. build/tmp/deploy/ipk/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-deploy-ipk"></a>4.2.15. <code class="filename">build/tmp/deploy/ipk/</code></h3></div></div></div><p>
This directory receives <code class="filename">.ipk</code> packages produced by
the build process.</p></div><div class="section" title="4.2.16. build/tmp/sysroots/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-sysroots"></a>4.2.16. <code class="filename">build/tmp/sysroots/</code></h3></div></div></div><p>
This directory contains shared header files and libraries as well as other shared
data.
Packages that need to share output with other packages do so within this directory.
The directory is subdivided by architecture so multiple builds can run within
the one build directory.
</p></div><div class="section" title="4.2.17. build/tmp/stamps/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-stamps"></a>4.2.17. <code class="filename">build/tmp/stamps/</code></h3></div></div></div><p>
This directory holds information that that BitBake uses for accounting purposes
to track what tasks have run and when they have run.
The directory is sub-divided by architecture.
The files in the directory are empty of data.
However, BitBake uses the filenames and timestamps for tracking purposes.
</p></div><div class="section" title="4.2.18. build/tmp/log/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-log"></a>4.2.18. <code class="filename">build/tmp/log/</code></h3></div></div></div><p>
This directory contains general logs that are not otherwise placed using the
package's <code class="filename"><a class="link" href="#var-WORKDIR" title="WORKDIR">WORKDIR</a></code>.
Examples of logs are the output from the <code class="filename">check_pkg</code> or
<code class="filename">distro_check</code> tasks.
Running a build does not necessarily mean this directory is created.
</p></div><div class="section" title="4.2.19. build/tmp/pkgdata/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-pkgdata"></a>4.2.19. <code class="filename">build/tmp/pkgdata/</code></h3></div></div></div><p>
This directory contains intermediate packaging data that is used later in the packaging process.
For more information, see the "<a class="link" href="#ref-classes-package" title="6.12. Packaging - package*.bbclass">Packaging - package*.bbclass</a>" section.
</p></div><div class="section" title="4.2.20. build/tmp/work/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-build-tmp-work"></a>4.2.20. <code class="filename">build/tmp/work/</code></h3></div></div></div><p>
This directory contains architecture-specific work sub-directories for packages built by BitBake.
All tasks execute from a work directory.
For example, the source for a particular package is unpacked, patched, configured and compiled all
within its own work directory.
Within the work directory, organization is based on the package group for which the source
is being compiled.
</p><p>
It is worth considering the structure of a typical work directory.
As an example, consider the <code class="filename">linux-yocto-kernel-3.0</code>
on the machine <code class="filename">qemux86</code>
built within the Yocto Project.
For this package, a work directory of
<code class="filename">tmp/work/qemux86-poky-linux/linux-yocto-3.0+git1+&lt;.....&gt;</code>,
referred to as <code class="filename"><a class="link" href="#var-WORKDIR" title="WORKDIR">WORKDIR</a></code>, is created.
Within this directory, the source is unpacked to
<code class="filename">linux-qemux86-standard-build</code> and then patched by Quilt
(see the
"<a class="link" href="#using-a-quilt-workflow" target="_top">Modifying Package
Source Code with Quilt</a>" section in the Yocto Project Development Manual.
Within the <code class="filename">linux-qemux86-standard-build</code> directory,
standard Quilt directories <code class="filename">linux-3.0/patches</code>
and <code class="filename">linux-3.0/.pc</code> are created,
and standard Quilt commands can be used.
</p><p>
There are other directories generated within WORKDIR.
The most important directory is WORKDIR<code class="filename">/temp/</code>, which has log files for each
task (<code class="filename">log.do_*.pid</code>) and contains the scripts BitBake runs for
each task (<code class="filename">run.do_*.pid</code>).
The WORKDIR<code class="filename">/image/</code> directory is where "make
install" places its output that is then split into sub-packages
within WORKDIR<code class="filename">/packages-split/</code>.
</p></div></div><div class="section" title="4.3. The Metadata - meta/"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="structure-meta"></a>4.3. The Metadata - <code class="filename">meta/</code></h2></div></div></div><p>
As mentioned previously, metadata is the core of the Yocto Project.
Metadata has several important subdivisions:
</p><div class="section" title="4.3.1. meta/classes/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-classes"></a>4.3.1. <code class="filename">meta/classes/</code></h3></div></div></div><p>
This directory contains the <code class="filename">*.bbclass</code> files.
Class files are used to abstract common code so it can be reused by multiple
packages.
Every package inherits the <code class="filename">base.bbclass</code> file.
Examples of other important classes are <code class="filename">autotools.bbclass</code>, which
in theory allows any Autotool-enabled package to work with the Yocto Project with minimal effort.
Another example is <code class="filename">kernel.bbclass</code> that contains common code and functions
for working with the Linux kernel.
Functions like image generation or packaging also have their specific class files
such as <code class="filename">image.bbclass</code>, <code class="filename">rootfs_*.bbclass</code> and
<code class="filename">package*.bbclass</code>.
</p></div><div class="section" title="4.3.2. meta/conf/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-conf"></a>4.3.2. <code class="filename">meta/conf/</code></h3></div></div></div><p>
This directory contains the core set of configuration files that start from
<code class="filename">bitbake.conf</code> and from which all other configuration
files are included.
See the include statements at the end of the file and you will note that even
<code class="filename">local.conf</code> is loaded from there.
While <code class="filename">bitbake.conf</code> sets up the defaults, you can often override
these by using the (<code class="filename">local.conf</code>) file, machine file or
the distribution configuration file.
</p></div><div class="section" title="4.3.3. meta/conf/machine/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-conf-machine"></a>4.3.3. <code class="filename">meta/conf/machine/</code></h3></div></div></div><p>
This directory contains all the machine configuration files.
If you set <code class="filename">MACHINE="qemux86"</code>,
the OpenEmbedded build system looks for a <code class="filename">qemux86.conf</code> file in this
directory.
The <code class="filename">include</code> directory contains various data common to multiple machines.
If you want to add support for a new machine to the Yocto Project, look in this directory.
</p></div><div class="section" title="4.3.4. meta/conf/distro/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-conf-distro"></a>4.3.4. <code class="filename">meta/conf/distro/</code></h3></div></div></div><p>
Any distribution-specific configuration is controlled from this directory.
For the Yocto Project, the <code class="filename">defaultsetup.conf</code> is the main file here.
This directory includes the versions and the
<code class="filename">SRCDATE</code> definitions for applications that are configured here.
An example of an alternative configuration might be <code class="filename">poky-bleeding.conf</code>.
Although this file mainly inherits its configuration from Poky.
</p></div><div class="section" title="4.3.5. meta/recipes-bsp/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-bsp"></a>4.3.5. <code class="filename">meta/recipes-bsp/</code></h3></div></div></div><p>
This directory contains anything linking to specific hardware or hardware
configuration information such as "u-boot" and "grub".
</p></div><div class="section" title="4.3.6. meta/recipes-connectivity/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-connectivity"></a>4.3.6. <code class="filename">meta/recipes-connectivity/</code></h3></div></div></div><p>
This directory contains libraries and applications related to communication with other devices.
</p></div><div class="section" title="4.3.7. meta/recipes-core/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-core"></a>4.3.7. <code class="filename">meta/recipes-core/</code></h3></div></div></div><p>
This directory contains what is needed to build a basic working Linux image
including commonly used dependencies.
</p></div><div class="section" title="4.3.8. meta/recipes-devtools/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-devtools"></a>4.3.8. <code class="filename">meta/recipes-devtools/</code></h3></div></div></div><p>
This directory contains tools that are primarily used by the build system.
The tools, however, can also be used on targets.
</p></div><div class="section" title="4.3.9. meta/recipes-extended/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-extended"></a>4.3.9. <code class="filename">meta/recipes-extended/</code></h3></div></div></div><p>
This directory contains non-essential applications that add features compared to the
alternatives in core.
You might need this directory for full tool functionality or for Linux Standard Base (LSB)
compliance.
</p></div><div class="section" title="4.3.10. meta/recipes-gnome/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-gnome"></a>4.3.10. <code class="filename">meta/recipes-gnome/</code></h3></div></div></div><p>
This directory contains all things related to the GTK+ application framework.
</p></div><div class="section" title="4.3.11. meta/recipes-graphics/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-graphics"></a>4.3.11. <code class="filename">meta/recipes-graphics/</code></h3></div></div></div><p>
This directory contains X and other graphically related system libraries
</p></div><div class="section" title="4.3.12. meta/recipes-kernel/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-kernel"></a>4.3.12. <code class="filename">meta/recipes-kernel/</code></h3></div></div></div><p>
This directory contains the kernel and generic applications and libraries that
have strong kernel dependencies.
</p></div><div class="section" title="4.3.13. meta/recipes-multimedia/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-multimedia"></a>4.3.13. <code class="filename">meta/recipes-multimedia/</code></h3></div></div></div><p>
This directory contains codecs and support utilities for audio, images and video.
</p></div><div class="section" title="4.3.14. meta/recipes-qt/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-qt"></a>4.3.14. <code class="filename">meta/recipes-qt/</code></h3></div></div></div><p>
This directory contains all things related to the Qt application framework.
</p></div><div class="section" title="4.3.15. meta/recipes-rt/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-rt"></a>4.3.15. <code class="filename">meta/recipes-rt/</code></h3></div></div></div><p>
This directory contains package and image recipes for using and testing
the <code class="filename">PREEMPT_RT</code> kernel.
</p></div><div class="section" title="4.3.16. meta/recipes-sato/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-sato"></a>4.3.16. <code class="filename">meta/recipes-sato/</code></h3></div></div></div><p>
This directory contains the Sato demo/reference UI/UX and its associated applications
and configuration data.
</p></div><div class="section" title="4.3.17. meta/recipes-support/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-support"></a>4.3.17. <code class="filename">meta/recipes-support/</code></h3></div></div></div><p>
This directory contains recipes that used by other recipes, but that are not directly
included in images (i.e. dependencies of other recipes).
</p></div><div class="section" title="4.3.18. meta/site/"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-site"></a>4.3.18. <code class="filename">meta/site/</code></h3></div></div></div><p>
This directory contains a list of cached results for various architectures.
Because certain "autoconf" test results cannot be determined when cross-compiling due to
the tests not able to run on a live system, the information in this directory is
passed to "autoconf" for the various architectures.
</p></div><div class="section" title="4.3.19. meta/recipes.txt"><div class="titlepage"><div><div><h3 class="title"><a id="structure-meta-recipes-txt"></a>4.3.19. <code class="filename">meta/recipes.txt</code></h3></div></div></div><p>
This file is a description of the contents of <code class="filename">recipes-*</code>.
</p></div></div></div>
<div class="chapter" title="Chapter 5. BitBake"><div class="titlepage"><div><div><h2 class="title"><a id="ref-bitbake"></a>Chapter 5. BitBake</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#ref-bitbake-parsing">5.1. Parsing</a></span></dt><dt><span class="section"><a href="#ref-bitbake-providers">5.2. Preferences and Providers</a></span></dt><dt><span class="section"><a href="#ref-bitbake-dependencies">5.3. Dependencies</a></span></dt><dt><span class="section"><a href="#ref-bitbake-tasklist">5.4. The Task List</a></span></dt><dt><span class="section"><a href="#ref-bitbake-runtask">5.5. Running a Task</a></span></dt><dt><span class="section"><a href="#ref-bitbake-commandline">5.6. BitBake Command Line</a></span></dt><dt><span class="section"><a href="#ref-bitbake-fetchers">5.7. Fetchers</a></span></dt></dl></div><p>
BitBake is a program written in Python that interprets the metadata used by the OpenEmbedded
build system.
At some point, developers wonder what actually happens when you enter:
</p><pre class="literallayout">
$ bitbake core-image-sato
</pre><p>
</p><p>
This chapter provides an overview of what happens behind the scenes from BitBake's perspective.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
BitBake strives to be a generic "task" executor that is capable of handling complex dependency relationships.
As such, it has no real knowledge of what the tasks being executed actually do.
BitBake just considers a list of tasks with dependencies and handles metadata
that consists of variables in a certain format that get passed to the tasks.
</div><div class="section" title="5.1. Parsing"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-bitbake-parsing"></a>5.1. Parsing</h2></div></div></div><p>
BitBake parses configuration files, classes, and <code class="filename">.bb</code> files.
</p><p>
The first thing BitBake does is look for the <code class="filename">bitbake.conf</code> file.
This file resides in the
<a class="link" href="#source-directory" target="_top">source directory</a>
within the <code class="filename">meta/conf/</code> directory.
BitBake finds it by examining its
<a class="link" href="#var-BBPATH" title="BBPATH"><code class="filename">BBPATH</code></a> environment
variable and looking for the <code class="filename">meta/conf/</code>
directory.
</p><p>
The <code class="filename">bitbake.conf</code> file lists other configuration
files to include from a <code class="filename">conf/</code>
directory below the directories listed in <code class="filename">BBPATH</code>.
In general, the most important configuration file from a user's perspective
is <code class="filename">local.conf</code>, which contains a user's customized
settings for the OpenEmbedded build environment.
Other notable configuration files are the distribution
configuration file (set by the
<code class="filename"><a class="link" href="#var-DISTRO" title="DISTRO">DISTRO</a></code> variable)
and the machine configuration file
(set by the
<code class="filename"><a class="link" href="#var-MACHINE" title="MACHINE">MACHINE</a></code> variable).
The <code class="filename">DISTRO</code> and <code class="filename">MACHINE</code> BitBake environment
variables are both usually set in
the <code class="filename">local.conf</code> file.
Valid distribution
configuration files are available in the <code class="filename">meta/conf/distro/</code> directory
and valid machine configuration
files in the <code class="filename">meta/conf/machine/</code> directory.
Within the <code class="filename">meta/conf/machine/include/</code>
directory are various <code class="filename">tune-*.inc</code> configuration files that provide common
"tuning" settings specific to and shared between particular architectures and machines.
</p><p>
After the parsing of the configuration files, some standard classes are included.
The <code class="filename">base.bbclass</code> file is always included.
Other classes that are specified in the configuration using the
<code class="filename"><a class="link" href="#var-INHERIT" title="INHERIT">INHERIT</a></code>
variable are also included.
Class files are searched for in a <code class="filename">classes</code> subdirectory
under the paths in <code class="filename">BBPATH</code> in the same way as
configuration files.
</p><p>
After classes are included, the variable
<code class="filename"><a class="link" href="#var-BBFILES" title="BBFILES">BBFILES</a></code>
is set, usually in
<code class="filename">local.conf</code>, and defines the list of places to search for
<code class="filename">.bb</code> files.
By default, the <code class="filename">BBFILES</code> variable specifies the
<code class="filename">meta/recipes-*/</code> directory within Poky.
Adding extra content to <code class="filename">BBFILES</code> is best achieved through the use of
BitBake layers as described in the
"<a class="link" href="#understanding-and-creating-layers" target="_top">Understanding and
Creating Layers</a>" section of the Yocto Project Development Manual.
</p><p>
BitBake parses each <code class="filename">.bb</code> file in <code class="filename">BBFILES</code> and
stores the values of various variables.
In summary, for each <code class="filename">.bb</code>
file the configuration plus the base class of variables are set, followed
by the data in the <code class="filename">.bb</code> file
itself, followed by any inherit commands that
<code class="filename">.bb</code> file might contain.
</p><p>
Because parsing <code class="filename">.bb</code> files is a time
consuming process, a cache is kept to speed up subsequent parsing.
This cache is invalid if the timestamp of the <code class="filename">.bb</code>
file itself changes, or if the timestamps of any of the include,
configuration or class files the <code class="filename">.bb</code>
file depends on changes.
</p></div><div class="section" title="5.2. Preferences and Providers"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-bitbake-providers"></a>5.2. Preferences and Providers</h2></div></div></div><p>
Once all the <code class="filename">.bb</code> files have been
parsed, BitBake starts to build the target (<code class="filename">core-image-sato</code>
in the previous section's example) and looks for providers of that target.
Once a provider is selected, BitBake resolves all the dependencies for
the target.
In the case of <code class="filename">core-image-sato</code>, it would lead to
<code class="filename">task-base.bb</code>,
which in turn leads to packages like <code class="filename">Contacts</code>,
<code class="filename">Dates</code> and <code class="filename">BusyBox</code>.
These packages in turn depend on <code class="filename">eglibc</code> and the toolchain.
</p><p>
Sometimes a target might have multiple providers.
A common example is "virtual/kernel", which is provided by each kernel package.
Each machine often selects the best kernel provider by using a line similar to the
following in the machine configuration file:
</p><pre class="literallayout">
PREFERRED_PROVIDER_virtual/kernel = "linux-yocto"
</pre><p>
The default <code class="filename"><a class="link" href="#var-PREFERRED_PROVIDER" title="PREFERRED_PROVIDER">PREFERRED_PROVIDER</a></code>
is the provider with the same name as the target.
</p><p>
Understanding how providers are chosen is made complicated by the fact
that multiple versions might exist.
BitBake defaults to the highest version of a provider.
Version comparisons are made using the same method as Debian.
You can use the
<code class="filename"><a class="link" href="#var-PREFERRED_VERSION" title="PREFERRED_VERSION">PREFERRED_VERSION</a></code>
variable to specify a particular version (usually in the distro configuration).
You can influence the order by using the
<code class="filename"><a class="link" href="#var-DEFAULT_PREFERENCE" title="DEFAULT_PREFERENCE">DEFAULT_PREFERENCE</a></code>
variable.
By default, files have a preference of "0".
Setting the <code class="filename">DEFAULT_PREFERENCE</code> to "-1" makes the
package unlikely to be used unless it is explicitly referenced.
Setting the <code class="filename">DEFAULT_PREFERENCE</code> to "1" makes it likely the package is used.
<code class="filename">PREFERRED_VERSION</code> overrides any <code class="filename">DEFAULT_PREFERENCE</code> setting.
<code class="filename">DEFAULT_PREFERENCE</code> is often used to mark newer and more experimental package
versions until they have undergone sufficient testing to be considered stable.
</p><p>
In summary, BitBake has created a list of providers, which is prioritized, for each target.
</p></div><div class="section" title="5.3. Dependencies"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-bitbake-dependencies"></a>5.3. Dependencies</h2></div></div></div><p>
Each target BitBake builds consists of multiple tasks such as
<code class="filename">fetch</code>, <code class="filename">unpack</code>,
<code class="filename">patch</code>, <code class="filename">configure</code>,
and <code class="filename">compile</code>.
For best performance on multi-core systems, BitBake considers each task as an independent
entity with its own set of dependencies.
</p><p>
Dependencies are defined through several variables.
You can find information about variables BitBake uses in the
<a class="ulink" href="http://docs.openembedded.org/bitbake/html/" target="_top">BitBake manual</a>.
At a basic level, it is sufficient to know that BitBake uses the
<code class="filename"><a class="link" href="#var-DEPENDS" title="DEPENDS">DEPENDS</a></code> and
<code class="filename"><a class="link" href="#var-RDEPENDS" title="RDEPENDS">RDEPENDS</a></code> variables when
calculating dependencies.
</p></div><div class="section" title="5.4. The Task List"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-bitbake-tasklist"></a>5.4. The Task List</h2></div></div></div><p>
Based on the generated list of providers and the dependency information,
BitBake can now calculate exactly what tasks it needs to run and in what
order it needs to run them.
The build now starts with BitBake forking off threads up to the limit set in the
<code class="filename"><a class="link" href="#var-BB_NUMBER_THREADS" title="BB_NUMBER_THREADS">BB_NUMBER_THREADS</a></code> variable.
BitBake continues to fork threads as long as there are tasks ready to run,
those tasks have all their dependencies met, and the thread threshold has not been
exceeded.
</p><p>
It is worth noting that you can greatly speed up the build time by properly setting
the <code class="filename">BB_NUMBER_THREADS</code> variable.
See the
"<a class="link" href="#building-image" target="_top">Building an Image</a>"
section in the Yocto Project Quick Start for more information.
</p><p>
As each task completes, a timestamp is written to the directory specified by the
<code class="filename"><a class="link" href="#var-STAMP" title="STAMP">STAMP</a></code> variable (usually
<code class="filename">build/tmp/stamps/*/</code>).
On subsequent runs, BitBake looks at the <code class="filename">/build/tmp/stamps</code>
directory and does not rerun
tasks that are already completed unless a timestamp is found to be invalid.
Currently, invalid timestamps are only considered on a per
<code class="filename">.bb</code> file basis.
So, for example, if the configure stamp has a timestamp greater than the
compile timestamp for a given target, then the compile task would rerun.
Running the compile task again, however, has no effect on other providers
that depend on that target.
This behavior could change or become configurable in future versions of BitBake.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Some tasks are marked as "nostamp" tasks.
No timestamp file is created when these tasks are run.
Consequently, "nostamp" tasks are always rerun.
</div></div><div class="section" title="5.5. Running a Task"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-bitbake-runtask"></a>5.5. Running a Task</h2></div></div></div><p>
Tasks can either be a shell task or a Python task.
For shell tasks, BitBake writes a shell script to
<code class="filename">${WORKDIR}/temp/run.do_taskname.pid</code> and then executes the script.
The generated shell script contains all the exported variables, and the shell functions
with all variables expanded.
Output from the shell script goes to the file <code class="filename">${WORKDIR}/temp/log.do_taskname.pid</code>.
Looking at the expanded shell functions in the run file and the output in the log files
is a useful debugging technique.
</p><p>
For Python tasks, BitBake executes the task internally and logs information to the
controlling terminal.
Future versions of BitBake will write the functions to files similar to the way
shell tasks are handled.
Logging will be handled in way similar to shell tasks as well.
</p><p>
Once all the tasks have been completed BitBake exits.
</p><p>
When running a task, BitBake tightly controls the execution environment
of the build tasks to make sure unwanted contamination from the build machine
cannot influence the build.
Consequently, if you do want something to get passed into the build
task's environment, you must take a few steps:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Tell BitBake to load what you want from the environment
into the data store.
You can do so through the <code class="filename">BB_ENV_WHITELIST</code>
variable.
For example, assume you want to prevent the build system from
accessing your <code class="filename">$HOME/.ccache</code> directory.
The following command tells BitBake to load
<code class="filename">CCACHE_DIR</code> from the environment into the data
store:
</p><pre class="literallayout">
export BB_ENV_EXTRAWHITE="$BB_ENV_EXTRAWHITE CCACHE_DIR"
</pre></li><li class="listitem"><p>Tell BitBake to export what you have loaded into the
environment store to the task environment of every running task.
Loading something from the environment into the data store
(previous step) only makes it available in the datastore.
To export it to the task environment of every running task,
use a command similar to the following in your
<code class="filename">local.conf</code> or distro configuration file:
</p><pre class="literallayout">
export CCACHE_DIR
</pre></li></ol></div><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
A side effect of the previous steps is that BitBake records the variable
as a dependency of the build process in things like the shared state
checksums.
If doing so results in unnecessary rebuilds of tasks, you can whitelist the
variable so that the shared state code ignores the dependency when it creates
checksums.
For information on this process, see the <code class="filename">BB_HASHBASE_WHITELIST</code>
example in the "<a class="link" href="#checksums" title="3.2.2. Checksums (Signatures)">Checksums (Signatures)</a>" section.
</div></div><div class="section" title="5.6. BitBake Command Line"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-bitbake-commandline"></a>5.6. BitBake Command Line</h2></div></div></div><p>
Following is the BitBake help output:
</p><pre class="screen">
$ bitbake --help
Usage: bitbake [options] [package ...]
Executes the specified task (default is 'build') for a given set of BitBake files.
It expects that BBFILES is defined, which is a space separated list of files to
be executed. BBFILES does support wildcards.
Default BBFILES are the .bb files in the current directory.
Options:
--version show program's version number and exit
-h, --help show this help message and exit
-b BUILDFILE, --buildfile=BUILDFILE
execute the task against this .bb file, rather than a
package from BBFILES. Does not handle any
dependencies.
-k, --continue continue as much as possible after an error. While the
target that failed, and those that depend on it,
cannot be remade, the other dependencies of these
targets can be processed all the same.
-a, --tryaltconfigs continue with builds by trying to use alternative
providers where possible.
-f, --force force run of specified cmd, regardless of stamp status
-c CMD, --cmd=CMD Specify task to execute. Note that this only executes
the specified task for the providee and the packages
it depends on, i.e. 'compile' does not implicitly call
stage for the dependencies (IOW: use only if you know
what you are doing). Depending on the base.bbclass a
listtasks tasks is defined and will show available
tasks
-r PREFILE, --read=PREFILE
read the specified file before bitbake.conf
-R POSTFILE, --postread=POSTFILE
read the specified file after bitbake.conf
-v, --verbose output more chit-chat to the terminal
-D, --debug Increase the debug level. You can specify this more
than once.
-n, --dry-run don't execute, just go through the motions
-S, --dump-signatures
don't execute, just dump out the signature
construction information
-p, --parse-only quit after parsing the BB files (developers only)
-s, --show-versions show current and preferred versions of all packages
-e, --environment show the global or per-package environment (this is
what used to be bbread)
-g, --graphviz emit the dependency trees of the specified packages in
the dot syntax
-I EXTRA_ASSUME_PROVIDED, --ignore-deps=EXTRA_ASSUME_PROVIDED
Assume these dependencies don't exist and are already
provided (equivalent to ASSUME_PROVIDED). Useful to
make dependency graphs more appealing
-l DEBUG_DOMAINS, --log-domains=DEBUG_DOMAINS
Show debug logging for the specified logging domains
-P, --profile profile the command and print a report
-u UI, --ui=UI userinterface to use
-t SERVERTYPE, --servertype=SERVERTYPE
Choose which server to use, none, process or xmlrpc
--revisions-changed Set the exit code depending on whether upstream
floating revisions have changed or not
</pre></div><div class="section" title="5.7. Fetchers"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-bitbake-fetchers"></a>5.7. Fetchers</h2></div></div></div><p>
BitBake also contains a set of "fetcher" modules that allow
retrieval of source code from various types of sources.
For example, BitBake can get source code from a disk with the metadata, from websites,
from remote shell accounts or from Source Code Management (SCM) systems
like <code class="filename">cvs/subversion/git</code>.
</p><p>
Fetchers are usually triggered by entries in
<code class="filename"><a class="link" href="#var-SRC_URI" title="SRC_URI">SRC_URI</a></code>.
You can find information about the options and formats of entries for specific
fetchers in the <a class="ulink" href="http://docs.openembedded.org/bitbake/html/" target="_top">BitBake manual</a>.
</p><p>
One useful feature for certain Source Code Manager (SCM) fetchers is the ability to
"auto-update" when the upstream SCM changes version.
Since this ability requires certain functionality from the SCM, not all
systems support it.
Currently Subversion, Bazaar and to a limited extent, Git support the ability to "auto-update".
This feature works using the <code class="filename"><a class="link" href="#var-SRCREV" title="SRCREV">SRCREV</a></code>
variable.
See the
"<a class="link" href="#platdev-appdev-srcrev" target="_top">Using an External SCM</a>" section
in the Yocto Project Development Manual for more information.
</p></div></div>
<div class="chapter" title="Chapter 6. Classes"><div class="titlepage"><div><div><h2 class="title"><a id="ref-classes"></a>Chapter 6. Classes</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#ref-classes-base">6.1. The base class - <code class="filename">base.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-autotools">6.2. Autotooled Packages - <code class="filename">autotools.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-update-alternatives">6.3. Alternatives - <code class="filename">update-alternatives.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-update-rc.d">6.4. Initscripts - <code class="filename">update-rc.d.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-binconfig">6.5. Binary config scripts - <code class="filename">binconfig.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-debian">6.6. Debian renaming - <code class="filename">debian.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-pkgconfig">6.7. Pkg-config - <code class="filename">pkgconfig.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-src-distribute">6.8. Distribution of sources - <code class="filename">src_distribute_local.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-perl">6.9. Perl modules - <code class="filename">cpan.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-distutils">6.10. Python extensions - <code class="filename">distutils.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-devshell">6.11. Developer Shell - <code class="filename">devshell.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-package">6.12. Packaging - <code class="filename">package*.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-kernel">6.13. Building kernels - <code class="filename">kernel.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-image">6.14. Creating images - <code class="filename">image.bbclass</code> and <code class="filename">rootfs*.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-sanity">6.15. Host System sanity checks - <code class="filename">sanity.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-insane">6.16. Generated output quality assurance checks - <code class="filename">insane.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-siteinfo">6.17. Autotools configuration data cache - <code class="filename">siteinfo.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-useradd">6.18. Adding Users - <code class="filename">useradd.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-externalsrc">6.19. Using External Source - <code class="filename">externalsrc.bbclass</code></a></span></dt><dt><span class="section"><a href="#ref-classes-others">6.20. Other Classes</a></span></dt></dl></div><p>
Class files are used to abstract common functionality and share it amongst multiple
<code class="filename">.bb</code> files.
Any metadata usually found in a <code class="filename">.bb</code> file can also be placed in a class
file.
Class files are identified by the extension <code class="filename">.bbclass</code> and are usually placed
in a <code class="filename">classes/</code> directory beneath the
<code class="filename">meta*/</code> directory found in the
<a class="link" href="#source-directory" target="_top">source directory</a>.
Class files can also be pointed to by BUILDDIR (e.g. <code class="filename">build/</code>)in the same way as
<code class="filename">.conf</code> files in the <code class="filename">conf</code> directory.
Class files are searched for in <a class="link" href="#var-BBPATH" title="BBPATH"><code class="filename">BBPATH</code></a>
using the same method by which <code class="filename">.conf</code> files are searched.
</p><p>
In most cases inheriting the class is enough to enable its features, although
for some classes you might need to set variables or override some of the
default behaviour.
</p><div class="section" title="6.1. The base class - base.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-base"></a>6.1. The base class - <code class="filename">base.bbclass</code></h2></div></div></div><p>
The base class is special in that every <code class="filename">.bb</code>
file inherits it automatically.
This class contains definitions for standard basic
tasks such as fetching, unpacking, configuring (empty by default), compiling
(runs any <code class="filename">Makefile</code> present), installing (empty by default) and packaging
(empty by default).
These classes are often overridden or extended by other classes
such as <code class="filename">autotools.bbclass</code> or <code class="filename">package.bbclass</code>.
The class also contains some commonly used functions such as <code class="filename">oe_runmake</code>.
</p></div><div class="section" title="6.2. Autotooled Packages - autotools.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-autotools"></a>6.2. Autotooled Packages - <code class="filename">autotools.bbclass</code></h2></div></div></div><p>
Autotools (<code class="filename">autoconf</code>, <code class="filename">automake</code>,
and <code class="filename">libtool</code>) bring standardization.
This class defines a set of tasks (configure, compile etc.) that
work for all Autotooled packages.
It should usually be enough to define a few standard variables
and then simply <code class="filename">inherit autotools</code>.
This class can also work with software that emulates Autotools.
For more information, see the
"<a class="link" href="#usingpoky-extend-addpkg-autotools" target="_top">Autotooled Package</a>"
section in the Yocto Project Development Manual.
</p><p>
It's useful to have some idea of how the tasks defined by this class work
and what they do behind the scenes.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename">do_configure</code> ‐ regenerates the
configure script (using <code class="filename">autoreconf</code>) and then launches it
with a standard set of arguments used during cross-compilation.
You can pass additional parameters to <code class="filename">configure</code> through the
<code class="filename"><a class="link" href="#var-EXTRA_OECONF" title="EXTRA_OECONF">EXTRA_OECONF</a></code> variable.
</p></li><li class="listitem"><p><code class="filename">do_compile</code> ‐ runs <code class="filename">make</code> with
arguments that specify the compiler and linker.
You can pass additional arguments through
the <code class="filename"><a class="link" href="#var-EXTRA_OEMAKE" title="EXTRA_OEMAKE">EXTRA_OEMAKE</a></code> variable.
</p></li><li class="listitem"><p><code class="filename">do_install</code> ‐ runs <code class="filename">make install</code>
and passes a DESTDIR option, which takes its value from the standard
<code class="filename"><a class="link" href="#var-DESTDIR" title="DESTDIR">DESTDIR</a></code> variable.
</p></li></ul></div><p>
</p></div><div class="section" title="6.3. Alternatives - update-alternatives.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-update-alternatives"></a>6.3. Alternatives - <code class="filename">update-alternatives.bbclass</code></h2></div></div></div><p>
Several programs can fulfill the same or similar function and be installed with the same name.
For example, the <code class="filename">ar</code> command is available from the
<code class="filename">busybox</code>, <code class="filename">binutils</code> and
<code class="filename">elfutils</code> packages.
The <code class="filename">update-alternatives.bbclass</code> class handles renaming the
binaries so that multiple packages can be installed without conflicts.
The <code class="filename">ar</code> command still works regardless of which packages are installed
or subsequently removed.
The class renames the conflicting binary in each package and symlinks the highest
priority binary during installation or removal of packages.
</p><p>
Four variables control this class:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename">ALTERNATIVE_NAME</code> ‐ The name of the
binary that is replaced (<code class="filename">ar</code> in this example).</p></li><li class="listitem"><p><code class="filename">ALTERNATIVE_LINK</code> ‐ The path to
the resulting binary (<code class="filename">/bin/ar</code> in this example).</p></li><li class="listitem"><p><code class="filename">ALTERNATIVE_PATH</code> ‐ The path to the
real binary (<code class="filename">/usr/bin/ar.binutils</code> in this example).</p></li><li class="listitem"><p><code class="filename">ALTERNATIVE_PRIORITY</code> ‐ The priority of
the binary.
The version with the most features should have the highest priority.</p></li></ul></div><p>
</p><p>
Currently, the OpenEmbedded build system supports only one binary per package.
</p></div><div class="section" title="6.4. Initscripts - update-rc.d.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-update-rc.d"></a>6.4. Initscripts - <code class="filename">update-rc.d.bbclass</code></h2></div></div></div><p>
This class uses <code class="filename">update-rc.d</code> to safely install an
initialization script on behalf of the package.
The OpenEmbedded build system takes care of details such as making sure the script is stopped before
a package is removed and started when the package is installed.
Three variables control this class:
<code class="filename"><a class="link" href="#var-INITSCRIPT_PACKAGES" title="INITSCRIPT_PACKAGES">INITSCRIPT_PACKAGES</a></code>,
<code class="filename"><a class="link" href="#var-INITSCRIPT_NAME" title="INITSCRIPT_NAME">INITSCRIPT_NAME</a></code> and
<code class="filename"><a class="link" href="#var-INITSCRIPT_PARAMS" title="INITSCRIPT_PARAMS">INITSCRIPT_PARAMS</a></code>.
See the variable links for details.
</p></div><div class="section" title="6.5. Binary config scripts - binconfig.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-binconfig"></a>6.5. Binary config scripts - <code class="filename">binconfig.bbclass</code></h2></div></div></div><p>
Before <code class="filename">pkg-config</code> had become widespread, libraries shipped shell
scripts to give information about the libraries and include paths needed
to build software (usually named <code class="filename">LIBNAME-config</code>).
This class assists any recipe using such scripts.
</p><p>
During staging, BitBake installs such scripts into the
<code class="filename">sysroots/</code> directory.
BitBake also changes all paths to point into the <code class="filename">sysroots/</code>
directory so all builds that use the script will use the correct
directories for the cross compiling layout.
</p></div><div class="section" title="6.6. Debian renaming - debian.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-debian"></a>6.6. Debian renaming - <code class="filename">debian.bbclass</code></h2></div></div></div><p>
This class renames packages so that they follow the Debian naming
policy (i.e. <code class="filename">eglibc</code> becomes <code class="filename">libc6</code>
and <code class="filename">eglibc-devel</code> becomes <code class="filename">libc6-dev</code>.
</p></div><div class="section" title="6.7. Pkg-config - pkgconfig.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-pkgconfig"></a>6.7. Pkg-config - <code class="filename">pkgconfig.bbclass</code></h2></div></div></div><p>
<code class="filename">pkg-config</code> brought standardization and this class aims to make its
integration smooth for all libraries that make use of it.
</p><p>
During staging, BitBake installs <code class="filename">pkg-config</code> data into the
<code class="filename">sysroots/</code> directory.
By making use of sysroot functionality within <code class="filename">pkg-config</code>,
this class no longer has to manipulate the files.
</p></div><div class="section" title="6.8. Distribution of sources - src_distribute_local.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-src-distribute"></a>6.8. Distribution of sources - <code class="filename">src_distribute_local.bbclass</code></h2></div></div></div><p>
Many software licenses require that source files be provided along with the binaries.
To simplify this process, two classes were created:
<code class="filename">src_distribute.bbclass</code> and
<code class="filename">src_distribute_local.bbclass</code>.
</p><p>
The results of these classes are <code class="filename">tmp/deploy/source/</code>
subdirs with sources sorted by
<code class="filename"><a class="link" href="#var-LICENSE" title="LICENSE">LICENSE</a></code> field.
If recipes list few licenses (or have entries like "Bitstream Vera"),
the source archive is placed in each license directory.
</p><p>
This class operates using three modes:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>copy:</em></span> Copies the files to the
distribute directory.</p></li><li class="listitem"><p><span class="emphasis"><em>symlink:</em></span> Symlinks the files to the
distribute directory.</p></li><li class="listitem"><p><span class="emphasis"><em>move+symlink:</em></span> Moves the files into
the distribute directory and then symlinks them back.</p></li></ul></div><p>
</p></div><div class="section" title="6.9. Perl modules - cpan.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-perl"></a>6.9. Perl modules - <code class="filename">cpan.bbclass</code></h2></div></div></div><p>
Recipes for Perl modules are simple.
These recipes usually only need to point to the source's archive and then inherit the
proper <code class="filename">.bbclass</code> file.
Building is split into two methods depending on which method the module authors used.
</p><p>
Modules that use old <code class="filename">Makefile.PL</code>-based build system require
<code class="filename">cpan.bbclass</code> in their recipes.
</p><p>
Modules that use <code class="filename">Build.PL</code>-based build system require
using <code class="filename">cpan_build.bbclass</code> in their recipes.
</p></div><div class="section" title="6.10. Python extensions - distutils.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-distutils"></a>6.10. Python extensions - <code class="filename">distutils.bbclass</code></h2></div></div></div><p>
Recipes for Python extensions are simple.
These recipes usually only need to point to the source's archive and then inherit
the proper <code class="filename">.bbclass</code> file.
Building is split into two methods dependling on which method the module authors used.
</p><p>
Extensions that use an Autotools-based build system require Autotools and
<code class="filename">distutils</code>-based <code class="filename">.bbclasse</code> files in their recipes.
</p><p>
Extensions that use <code class="filename">distutils</code>-based build systems require
<code class="filename">distutils.bbclass</code> in their recipes.
</p></div><div class="section" title="6.11. Developer Shell - devshell.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-devshell"></a>6.11. Developer Shell - <code class="filename">devshell.bbclass</code></h2></div></div></div><p>
This class adds the <code class="filename">devshell</code> task.
Distribution policy dictates whether to include this class.
See the
"<a class="link" href="#platdev-appdev-devshell" target="_top">Using a Development Shell</a>" section
in the Yocto Project Development Manual for more information about using <code class="filename">devshell</code>.
</p></div><div class="section" title="6.12. Packaging - package*.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-package"></a>6.12. Packaging - <code class="filename">package*.bbclass</code></h2></div></div></div><p>
The packaging classes add support for generating packages from a build's
output.
The core generic functionality is in <code class="filename">package.bbclass</code>.
The code specific to particular package types is contained in various sub-classes such as
<code class="filename">package_deb.bbclass</code>, <code class="filename">package_ipk.bbclass</code>,
and <code class="filename">package_rpm.bbclass</code>.
Most users will want one or more of these classes.
</p><p>
You can control the list of resulting package formats by using the
<code class="filename"><a class="link" href="#var-PACKAGE_CLASSES" title="PACKAGE_CLASSES">PACKAGE_CLASSES</a></code>
variable defined in the <code class="filename">local.conf</code> configuration file,
which is located in the <code class="filename">conf</code> folder of the
<a class="link" href="#source-directory" target="_top">source directory</a>.
When defining the variable, you can specify one or more package types.
Since images are generated from packages, a packaging class is
needed to enable image generation.
The first class listed in this variable is used for image generation.
</p><p>
The package class you choose can affect build-time performance and has space
ramifications.
In general, building a package with RPM takes about thirty percent more time as
compared to using IPK to build the same or similar package.
This comparison takes into account a complete build of the package with all
dependencies previously built.
The reason for this discrepancy is because the RPM package manager creates and
processes more metadata than the IPK package manager.
Consequently, you might consider setting <code class="filename">PACKAGE_CLASSES</code>
to "package_ipk" if you are building smaller systems.
</p><p>
Keep in mind, however, that RPM starts to provide more abilities than IPK due to
the fact that it processes more metadata.
For example, this information includes individual file types, file checksum generation
and evaluation on install, sparse file support, conflict detection and resolution
for multilib systems, ACID style upgrade, and repackaging abilities for rollbacks.
</p><p>
Another consideration for packages built using the RPM package manager is space.
For smaller systems, the extra space used for the Berkley Database and the amount
of metadata can affect your ability to do on-device upgrades.
</p><p>
You can find additional information on the effects of the package class at these
two Yocto Project mailing list links:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><a class="ulink" href="http://lists.yoctoproject.org/pipermail/poky/2011-May/006362.html" target="_top">
https://lists.yoctoproject.org/pipermail/poky/2011-May/006362.html</a></p></li><li class="listitem"><p><a class="ulink" href="http://lists.yoctoproject.org/pipermail/poky/2011-May/006363.html" target="_top">
https://lists.yoctoproject.org/pipermail/poky/2011-May/006363.html</a></p></li></ul></div><p>
</p></div><div class="section" title="6.13. Building kernels - kernel.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-kernel"></a>6.13. Building kernels - <code class="filename">kernel.bbclass</code></h2></div></div></div><p>
This class handles building Linux kernels.
The class contains code to build all kernel trees.
All needed headers are staged into the
<code class="filename"><a class="link" href="#var-STAGING_KERNEL_DIR" title="STAGING_KERNEL_DIR">STAGING_KERNEL_DIR</a></code>
directory to allow out-of-tree module builds using <code class="filename">module.bbclass</code>.
</p><p>
This means that each built kernel module is packaged separately and inter-module
dependencies are created by parsing the <code class="filename">modinfo</code> output.
If all modules are required, then installing the <code class="filename">kernel-modules</code>
package installs all packages with modules and various other kernel packages
such as <code class="filename">kernel-vmlinux</code>.
</p><p>
Various other classes are used by the kernel and module classes internally including
<code class="filename">kernel-arch.bbclass</code>, <code class="filename">module_strip.bbclass</code>,
<code class="filename">module-base.bbclass</code>, and <code class="filename">linux-kernel-base.bbclass</code>.
</p></div><div class="section" title="6.14. Creating images - image.bbclass and rootfs*.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-image"></a>6.14. Creating images - <code class="filename">image.bbclass</code> and <code class="filename">rootfs*.bbclass</code></h2></div></div></div><p>
These classes add support for creating images in several formats.
First, the root filesystem is created from packages using
one of the <code class="filename">rootfs_*.bbclass</code>
files (depending on the package format used) and then the image is created.
</p><p>
The <code class="filename"><a class="link" href="#var-IMAGE_FSTYPES" title="IMAGE_FSTYPES">IMAGE_FSTYPES</a></code>
variable controls the types of images to generate.
</p><p>
The <code class="filename"><a class="link" href="#var-IMAGE_INSTALL" title="IMAGE_INSTALL">IMAGE_INSTALL</a></code>
variable controls the list of packages to install into the image.
</p></div><div class="section" title="6.15. Host System sanity checks - sanity.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-sanity"></a>6.15. Host System sanity checks - <code class="filename">sanity.bbclass</code></h2></div></div></div><p>
This class checks to see if prerequisite software is present so that
users can be notified of potential problems that might affect their build.
The class also performs basic user configuration checks from
the <code class="filename">local.conf</code> configuration file to
prevent common mistakes that cause build failures.
Distribution policy usually determines whether to include this class.
</p></div><div class="section" title="6.16. Generated output quality assurance checks - insane.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-insane"></a>6.16. Generated output quality assurance checks - <code class="filename">insane.bbclass</code></h2></div></div></div><p>
This class adds a step to the package generation process that sanity checks the
packages generated by the OpenEmbedded build system.
A range of checks are performed that check the build's output
for common problems that show up during runtime.
Distribution policy usually dictates whether to include this class.
</p><p>
You can configure the sanity checks so that specific test failures either raise a warning or
an error message.
Typically, failures for new tests generate a warning.
Subsequent failures for the same test would then generate an error message
once the metadata is in a known and good condition.
You use the <code class="filename">WARN_QA</code> variable to specify tests for which you
want to generate a warning message on failure.
You use the <code class="filename">ERROR_QA</code> variable to specify tests for which you
want to generate an error message on failure.
</p><p>
The following list shows the tests you can list with the <code class="filename">WARN_QA</code>
and <code class="filename">ERROR_QA</code> variables:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><code class="filename">ldflags:</code></em></span>
Ensures that the binaries were linked with the
<code class="filename">LDFLAGS</code> options provided by the build system.
If this test fails, check that the <code class="filename">LDFLAGS</code> variable
is being passed to the linker command.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">useless-rpaths:</code></em></span>
Checks for dynamic library load paths (rpaths) in the binaries that
by default on a standard system are searched by the linker (e.g.
<code class="filename">/lib</code> and <code class="filename">/usr/lib</code>).
While these paths will not cause any breakage, they do waste space and
are unnecessary.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">rpaths:</code></em></span>
Checks for rpaths in the binaries that contain build system paths such
as <code class="filename">TMPDIR</code>.
If this test fails, bad <code class="filename">-rpath</code> options are being
passed to the linker commands and your binaries have potential security
issues.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">dev-so:</code></em></span>
Checks that the <code class="filename">.so</code> symbolic links are in the
<code class="filename">-dev</code> package and not in any of the other packages.
In general, these symlinks are only useful for development purposes.
Thus, the <code class="filename">-dev</code> package is the correct location for
them.
Some very rare cases do exist for dynamically loaded modules where
these symlinks are needed instead in the main package.
</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">debug-files:</code></em></span>
Checks for <code class="filename">.debug</code> directories in anything but the
<code class="filename">-dbg</code> package.
The debug files should all be in the <code class="filename">-dbg</code> package.
Thus, anything packaged elsewhere is incorrect packaging.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">arch:</code></em></span>
Checks the Executable and Linkable Format (ELF) type, bit size and endianness
of any binaries to ensure it matches the target architecture.
This test fails if any binaries don't match the type since there would be an
incompatibility.
Sometimes software, like bootloaders, might need to bypass this check.
</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">debug-deps:</code></em></span>
Checks that <code class="filename">-dbg</code> packages only depend on other
<code class="filename">-dbg</code> packages and not on any other types of packages,
which would cause a packaging bug.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">dev-deps:</code></em></span>
Checks that <code class="filename">-dev</code> packages only depend on other
<code class="filename">-dev</code> packages and not on any other types of packages,
which would be a packaging bug.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">pkgconfig:</code></em></span>
Checks <code class="filename">.pc</code> files for any
<code class="filename">TMPDIR/WORKDIR</code> paths.
Any <code class="filename">.pc</code> file containing these paths is incorrect
since <code class="filename">pkg-config</code> itself adds the correct sysroot prefix
when the files are accessed.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">la:</code></em></span>
Checks <code class="filename">.la</code> files for any <code class="filename">TMPDIR</code>
paths.
Any <code class="filename">.la</code> file continaing these paths is incorrect since
<code class="filename">libtool</code> adds the correct sysroot prefix when using the
files automatically itself.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">desktop:</code></em></span>
Runs the <code class="filename">desktop-file-validate</code> program against any
<code class="filename">.desktop</code> files to validate their contents against
the specification for <code class="filename">.desktop</code> files.</p></li></ul></div><p>
</p></div><div class="section" title="6.17. Autotools configuration data cache - siteinfo.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-siteinfo"></a>6.17. Autotools configuration data cache - <code class="filename">siteinfo.bbclass</code></h2></div></div></div><p>
Autotools can require tests that must execute on the target hardware.
Since this is not possible in general when cross compiling, site information is
used to provide cached test results so these tests can be skipped over but
still make the correct values available.
The <code class="filename"><a class="link" href="#structure-meta-site" title="4.3.18. meta/site/">meta/site directory</a></code>
contains test results sorted into different categories such as architecture, endianness, and
the <code class="filename">libc</code> used.
Site information provides a list of files containing data relevant to
the current build in the
<code class="filename"><a class="link" href="#var-CONFIG_SITE" title="CONFIG_SITE">CONFIG_SITE</a></code> variable
that Autotools automatically picks up.
</p><p>
The class also provides variables like
<code class="filename"><a class="link" href="#var-SITEINFO_ENDIANNESS" title="SITEINFO_ENDIANNESS">SITEINFO_ENDIANNESS</a></code>
and <code class="filename"><a class="link" href="#var-SITEINFO_BITS" title="SITEINFO_BITS">SITEINFO_BITS</a></code>
that can be used elsewhere in the metadata.
</p><p>
Because this class is included from <code class="filename">base.bbclass</code>, it is always active.
</p></div><div class="section" title="6.18. Adding Users - useradd.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-useradd"></a>6.18. Adding Users - <code class="filename">useradd.bbclass</code></h2></div></div></div><p>
If you have packages that install files that are owned by custom users or groups,
you can use this class to specify those packages and associate the users and groups
with those packages.
The <code class="filename">meta-skeleton/recipes-skeleton/useradd/useradd-example.bb</code>
recipe in the <a class="link" href="#source-directory" target="_top">source directory</a>
provides a simple exmample that shows how to add three
users and groups to two packages.
See the <code class="filename">useradd-example.bb</code> for more information on how to
use this class.
</p></div><div class="section" title="6.19. Using External Source - externalsrc.bbclass"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-externalsrc"></a>6.19. Using External Source - <code class="filename">externalsrc.bbclass</code></h2></div></div></div><p>
You can use this class to build software from source code that is external to the
OpenEmbedded build system.
In other words, your source code resides in an external tree outside of the Yocto Project.
Building software from an external source tree means that the normal fetch, unpack, and
patch process is not used.
</p><p>
To use the class, you need to define the
<a class="link" href="#var-S" title="S"><code class="filename">S</code></a> variable to point to the directory that contains the source files.
You also need to have your recipe inherit the <code class="filename">externalsrc.bbclass</code> class.
</p><p>
This class expects the source code to support recipe builds that use the
<a class="link" href="#var-B" title="B"><code class="filename">B</code></a> variable to point to the directory in
which the OpenEmbedded build system places the generated objects built from the recipes.
By default, the <code class="filename">B</code> directory is set to the following, which is separate from the
source directory (<code class="filename">S</code>):
</p><pre class="literallayout">
${WORKDIR}/${BPN}-{PV}/
</pre><p>
See the glossary entries for the
<a class="link" href="#var-WORKDIR" title="WORKDIR"><code class="filename">WORKDIR</code></a>,
<a class="link" href="#var-BPN" title="BPN"><code class="filename">BPN</code></a>,
<a class="link" href="#var-PV" title="PV"><code class="filename">PV</code></a>,
<a class="link" href="#var-S" title="S"><code class="filename">S</code></a>, and
<a class="link" href="#var-B" title="B"><code class="filename">B</code></a> for more information.
</p><p>
You can build object files in the external tree by setting the
<code class="filename">B</code> variable equal to <code class="filename">"${S}"</code>.
However, this practice does not work well if you use the source for more than one variant
(i.e., "natives" such as <code class="filename">quilt-native</code>,
or "crosses" such as <code class="filename">gcc-cross</code>).
So, be sure there are no "native", "cross", or "multilib" variants of the recipe.
</p><p>
If you do want to build different variants of a recipe, you can use the
<a class="link" href="#var-BBCLASSEXTEND" title="BBCLASSEXTEND"><code class="filename">BBCLASSEXTEND</code></a> variable.
When you do, the <a class="link" href="#var-B" title="B"><code class="filename">B</code></a> variable must support the
recipe's ability to build variants in different working directories.
Most autotools-based recipes support separating these directories.
The OpenEmbedded build system defaults to using separate directories for <code class="filename">gcc</code>
and some kernel recipes.
Alternatively, you can make sure that separate recipes exist that each
use the <code class="filename">BBCLASSEXTEND</code> variable to build each variant.
The separate recipes can inherit a single target recipe.
</p><p>
For information on how to use this class, see the
"<a class="link" href="#building-software-from-an-external-source" target="_top">Building
Software from an External Source</a>" section in the Yocto Project Development Manual.
</p></div><div class="section" title="6.20. Other Classes"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-classes-others"></a>6.20. Other Classes</h2></div></div></div><p>
Thus far, this chapter has discussed only the most useful and important
classes.
However, other classes exist within the <code class="filename">meta/classes</code> directory
in the <a class="link" href="#source-directory" target="_top">source directory</a>.
You can examine the <code class="filename">.bbclass</code> files directly for more
information.
</p></div></div>
<div class="chapter" title="Chapter 7. Images"><div class="titlepage"><div><div><h2 class="title"><a id="ref-images"></a>Chapter 7. Images</h2></div></div></div><p>
The OpenEmbedded build process supports several types of images to satisfy different needs.
When you issue the <code class="filename">bitbake</code> command you provide a “top-level” recipe
that essentially begins the build for the type of image you want.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
Building an image without GNU Public License Version 3 (GPLv3) components is
only supported for minimal and base images.
Furthermore, if you are going to build an image using non-GPLv3 components,
you must make the following changes in the <code class="filename">local.conf</code> file
before using the BitBake command to build the minimal or base image:
<pre class="literallayout">
1. Comment out the EXTRA_IMAGE_FEATURES line
2. Set INCOMPATIBLE_LICENSE = "GPLv3"
</pre></div><p>
From within the <code class="filename">poky</code> Git repository, use the following command to list
the supported images:
</p><pre class="literallayout">
$ ls meta*/recipes*/images/*.bb
</pre><p>
These recipes reside in the <code class="filename">meta/recipes-core/images</code>,
<code class="filename">meta/recipes-extended/images</code>,
<code class="filename">meta/recipes-graphics/images</code>, and
<code class="filename">meta/recipes-sato/images</code> directories
within the <a class="link" href="#source-directory" target="_top">source directory</a>.
Although the recipe names are somewhat explanatory, here is a list that describes them:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-base</code>:</em></span>
A console-only image that fully supports the target device hardware.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-core</code>:</em></span>
An X11 image with simple applications such as terminal, editor, and file manager.
</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-minimal</code>:</em></span>
A small image just capable of allowing a device to boot.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-minimal-dev</code>:</em></span>
A <code class="filename">core-image-minimal</code> image suitable for development work
using the host.
The image includes headers and libraries you can use in a host development
environment.
</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-minimal-initramfs</code>:</em></span>
A <code class="filename">core-image-minimal</code> image that has the Minimal RAM-based
Initial Root Filesystem (<code class="filename">initramfs</code>) as part of the kernel,
which allows the system to find the first “init” program more efficiently.
</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-minimal-mtdutils</code>:</em></span>
A <code class="filename">core-image-minimal</code> image that has support
for the Minimal MTD Utilities, which let the user interact with the
MTD subsystem in the kernel to perform operations on flash devices.
</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-basic</code>:</em></span>
A foundational basic image without support for X that can be reasonably used for
customization.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-lsb</code>:</em></span>
A <code class="filename">core-image-basic</code> image suitable for implementations
that conform to Linux Standard Base (LSB).</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-lsb-dev</code>:</em></span>
A <code class="filename">core-image-lsb</code> image that is suitable for development work
using the host.
The image includes headers and libraries you can use in a host development
environment.
</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-lsb-sdk</code>:</em></span>
A <code class="filename">core-image-lsb</code> that includes everything in meta-toolchain
but also includes development headers and libraries to form a complete standalone SDK.
This image is suitable for development using the target.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-clutter</code>:</em></span>
An image with support for the Open GL-based toolkit Clutter, which enables development of
rich and animated graphical user interfaces.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-sato</code>:</em></span>
An image with Sato support, a mobile environment and visual style that works well
with mobile devices.
The image supports X11 with a Sato theme and Pimlico applications and also
contains terminal, editor, and file manager.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-sato-dev</code>:</em></span>
A <code class="filename">core-image-sato</code> image suitable for development
using the host.
The image includes libraries needed to build applications on the device itself,
testing and profiling tools, and debug symbols.
This image was formerly <code class="filename">core-image-sdk</code>.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-sato-sdk</code>:</em></span>
A <code class="filename">core-image-sato</code> image that includes everything in meta-toolchain.
The image also includes development headers and libraries to form a complete standalone SDK
and is suitable for development using the target.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-rt</code>:</em></span>
A <code class="filename">core-image-minimal</code> image plus a real-time test suite and
tools appropriate for real-time use.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-rt-sdk</code>:</em></span>
A <code class="filename">core-image-rt</code> image that includes everything in
<code class="filename">meta-toolchain</code>.
The image also includes development headers and libraries to form a complete
stand-alone SDK and is suitable for development using the target.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">core-image-gtk-directfb</code>:</em></span>
An image that uses <code class="filename">gtk+</code> over <code class="filename">directfb</code>
instead of X11.
In order to build, this image requires specific distro configuration that enables
<code class="filename">gtk</code> over <code class="filename">directfb</code>.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">build-appliance-image</code>:</em></span>
An image you can boot and run using either the
<a class="ulink" href="http://www.vmware.com/products/player/overview.html" target="_top">VMware Player</a>
or <a class="ulink" href="http://www.vmware.com/products/workstation/overview.html" target="_top">VMware Workstation</a>.
For more information on this image, see the
<a class="ulink" href="http://www.yoctoproject.org/documentation/build-appliance" target="_top">Build Appliance</a> page on
the Yocto Project website.</p></li></ul></div><div class="tip" title="Tip" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Tip</h3>
From the Yocto Project release 1.1 onwards, <code class="filename">-live</code> and
<code class="filename">-directdisk</code> images have been replaced by a "live"
option in <code class="filename">IMAGE_FSTYPES</code> that will work with any image to produce an
image file that can be
copied directly to a CD or USB device and run as is.
To build a live image, simply add
"live" to <code class="filename">IMAGE_FSTYPES</code> within the <code class="filename">local.conf</code>
file or wherever appropriate and then build the desired image as normal.
</div></div>
<div class="chapter" title="Chapter 8. Reference: Features"><div class="titlepage"><div><div><h2 class="title"><a id="ref-features"></a>Chapter 8. Reference: Features</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#ref-features-distro">8.1. Distro</a></span></dt><dt><span class="section"><a href="#ref-features-machine">8.2. Machine</a></span></dt><dt><span class="section"><a href="#ref-features-image">8.3. Reference: Images</a></span></dt></dl></div><p>
Features provide a mechanism for working out which packages
should be included in the generated images.
Distributions can select which features they want to support through the
<code class="filename"><a class="link" href="#var-DISTRO_FEATURES" title="DISTRO_FEATURES">DISTRO_FEATURES</a></code>
variable, which is set in the <code class="filename">poky.conf</code> distribution configuration file.
Machine features are set in the
<code class="filename"><a class="link" href="#var-MACHINE_FEATURES" title="MACHINE_FEATURES">MACHINE_FEATURES</a></code>
variable, which is set in the machine configuration file and
specifies the hardware features for a given machine.
</p><p>
These two variables combine to work out which kernel modules,
utilities, and other packages to include.
A given distribution can support a selected subset of features so some machine features might not
be included if the distribution itself does not support them.
</p><div class="section" title="8.1. Distro"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-features-distro"></a>8.1. Distro</h2></div></div></div><p>
The items below are valid options for
<code class="filename"><a class="link" href="#var-DISTRO_FEATURES" title="DISTRO_FEATURES">DISTRO_FEATURES</a></code>:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>alsa:</em></span> ALSA support will be included (OSS compatibility
kernel modules will be installed if available).</p></li><li class="listitem"><p><span class="emphasis"><em>bluetooth:</em></span> Include bluetooth support (integrated BT only)
</p></li><li class="listitem"><p><span class="emphasis"><em>ext2:</em></span> Include tools for supporting for devices with internal
HDD/Microdrive for storing files (instead of Flash only devices)
</p></li><li class="listitem"><p><span class="emphasis"><em>irda:</em></span> Include Irda support
</p></li><li class="listitem"><p><span class="emphasis"><em>keyboard:</em></span> Include keyboard support (e.g. keymaps will be
loaded during boot).
</p></li><li class="listitem"><p><span class="emphasis"><em>pci:</em></span> Include PCI bus support
</p></li><li class="listitem"><p><span class="emphasis"><em>pcmcia:</em></span> Include PCMCIA/CompactFlash support
</p></li><li class="listitem"><p><span class="emphasis"><em>usbgadget:</em></span> USB Gadget Device support (for USB
networking/serial/storage)
</p></li><li class="listitem"><p><span class="emphasis"><em>usbhost:</em></span> USB Host support (allows to connect external
keyboard, mouse, storage, network etc)
</p></li><li class="listitem"><p><span class="emphasis"><em>wifi:</em></span> WiFi support (integrated only)
</p></li><li class="listitem"><p><span class="emphasis"><em>cramfs:</em></span> CramFS support
</p></li><li class="listitem"><p><span class="emphasis"><em>ipsec:</em></span> IPSec support
</p></li><li class="listitem"><p><span class="emphasis"><em>ipv6:</em></span> IPv6 support
</p></li><li class="listitem"><p><span class="emphasis"><em>nfs:</em></span> NFS client support (for mounting NFS exports on
device)</p></li><li class="listitem"><p><span class="emphasis"><em>ppp:</em></span> PPP dialup support</p></li><li class="listitem"><p><span class="emphasis"><em>smbfs:</em></span> SMB networks client support (for mounting
Samba/Microsoft Windows shares on device)</p></li></ul></div><p>
</p></div><div class="section" title="8.2. Machine"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-features-machine"></a>8.2. Machine</h2></div></div></div><p>
The items below are valid options for
<code class="filename"><a class="link" href="#var-MACHINE_FEATURES" title="MACHINE_FEATURES">MACHINE_FEATURES</a></code>:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>acpi:</em></span> Hardware has ACPI (x86/x86_64 only)
</p></li><li class="listitem"><p><span class="emphasis"><em>alsa:</em></span> Hardware has ALSA audio drivers
</p></li><li class="listitem"><p><span class="emphasis"><em>apm:</em></span> Hardware uses APM (or APM emulation)
</p></li><li class="listitem"><p><span class="emphasis"><em>bluetooth:</em></span> Hardware has integrated BT
</p></li><li class="listitem"><p><span class="emphasis"><em>ext2:</em></span> Hardware HDD or Microdrive
</p></li><li class="listitem"><p><span class="emphasis"><em>irda:</em></span> Hardware has Irda support
</p></li><li class="listitem"><p><span class="emphasis"><em>keyboard:</em></span> Hardware has a keyboard
</p></li><li class="listitem"><p><span class="emphasis"><em>pci:</em></span> Hardware has a PCI bus
</p></li><li class="listitem"><p><span class="emphasis"><em>pcmcia:</em></span> Hardware has PCMCIA or CompactFlash sockets
</p></li><li class="listitem"><p><span class="emphasis"><em>screen:</em></span> Hardware has a screen
</p></li><li class="listitem"><p><span class="emphasis"><em>serial:</em></span> Hardware has serial support (usually RS232)
</p></li><li class="listitem"><p><span class="emphasis"><em>touchscreen:</em></span> Hardware has a touchscreen
</p></li><li class="listitem"><p><span class="emphasis"><em>usbgadget:</em></span> Hardware is USB gadget device capable
</p></li><li class="listitem"><p><span class="emphasis"><em>usbhost:</em></span> Hardware is USB Host capable
</p></li><li class="listitem"><p><span class="emphasis"><em>wifi:</em></span> Hardware has integrated WiFi
</p></li></ul></div><p>
</p></div><div class="section" title="8.3. Reference: Images"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-features-image"></a>8.3. Reference: Images</h2></div></div></div><p>
The contents of images generated by the OpenEmbedded build system can be controlled by the
<code class="filename"><a class="link" href="#var-IMAGE_FEATURES" title="IMAGE_FEATURES">IMAGE_FEATURES</a></code>
and <code class="filename"><a class="link" href="#var-EXTRA_IMAGE_FEATURES" title="EXTRA_IMAGE_FEATURES">EXTRA_IMAGE_FEATURES</a></code>
variables that you typically configure in your image recipes.
Through these variables you can add several different
predefined packages such as development utilities or packages with debug
information needed to investigate application problems or profile applications.
</p><p>
Current list of
<code class="filename">IMAGE_FEATURES</code> contains the following:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>apps-console-core:</em></span> Core console applications such as
<code class="filename">ssh</code>, <code class="filename">daemon</code>, <code class="filename">avahi daemon</code>,
<code class="filename">portmap</code> (for mounting NFS shares)</p></li><li class="listitem"><p><span class="emphasis"><em>x11-base:</em></span> X11 server + minimal desktop</p></li><li class="listitem"><p><span class="emphasis"><em>x11-sato:</em></span> OpenedHand Sato environment</p></li><li class="listitem"><p><span class="emphasis"><em>apps-x11-core:</em></span> Core X11 applications such as an
X Terminal, file manager, and file editor</p></li><li class="listitem"><p><span class="emphasis"><em>apps-x11-games:</em></span> A set of X11 games</p></li><li class="listitem"><p><span class="emphasis"><em>tools-sdk:</em></span> A full SDK that runs on the device
</p></li><li class="listitem"><p><span class="emphasis"><em>tools-debug:</em></span> Debugging tools such as
<code class="filename">strace</code> and <code class="filename">gdb</code>
</p></li><li class="listitem"><p><span class="emphasis"><em>tools-profile:</em></span> Profiling tools such as
<code class="filename">oprofile</code>, <code class="filename">exmap</code>, and
<code class="filename">LTTng</code></p></li><li class="listitem"><p><span class="emphasis"><em>tools-testapps:</em></span> Device testing tools (e.g.
touchscreen debugging)</p></li><li class="listitem"><p><span class="emphasis"><em>nfs-server:</em></span> NFS server (exports / over NFS
to everybody)</p></li><li class="listitem"><p><span class="emphasis"><em>dev-pkgs:</em></span> Development packages (headers and
extra library links) for all packages installed in a given image</p></li><li class="listitem"><p><span class="emphasis"><em>dbg-pkgs:</em></span> Debug packages for all packages
installed in a given image</p></li></ul></div><p>
</p></div></div>
<div class="chapter" title="Chapter 9. Variables Glossary"><div class="titlepage"><div><div><h2 class="title"><a id="ref-variables-glos"></a>Chapter 9. Variables Glossary</h2></div></div></div><div class="toc"><dl><dt><span class="glossary"><a href="#ref-variables-glossary">Glossary</a></span></dt></dl></div><p>
This chapter lists common variables used in the OpenEmbedded build system and gives an overview
of their function and contents.
</p><div class="glossary" title="Glossary"><div class="titlepage"><div><div><h2 class="title"><a id="ref-variables-glossary"></a>Glossary</h2></div></div></div><p>
<a class="link" href="#var-ALLOW_EMPTY" title="ALLOW_EMPTY">A</a>
<a class="link" href="#var-B" title="B">B</a>
<a class="link" href="#var-CFLAGS" title="CFLAGS">C</a>
<a class="link" href="#var-D" title="D">D</a>
<a class="link" href="#var-ENABLE_BINARY_LOCALE_GENERATION" title="ENABLE_BINARY_LOCALE_GENERATION">E</a>
<a class="link" href="#var-FILES" title="FILES">F</a>
<a class="link" href="#var-HOMEPAGE" title="HOMEPAGE">H</a>
<a class="link" href="#var-IMAGE_FEATURES" title="IMAGE_FEATURES">I</a>
<a class="link" href="#var-KBRANCH" title="KBRANCH">K</a>
<a class="link" href="#var-LAYERDIR" title="LAYERDIR">L</a>
<a class="link" href="#var-MACHINE" title="MACHINE">M</a>
<a class="link" href="#var-PACKAGE_ARCH" title="PACKAGE_ARCH">P</a>
<a class="link" href="#var-RCONFLICTS" title="RCONFLICTS">R</a>
<a class="link" href="#var-S" title="S">S</a>
<a class="link" href="#var-TARGET_ARCH" title="TARGET_ARCH">T</a>
<a class="link" href="#var-WORKDIR" title="WORKDIR">W</a>
</p><div class="glossdiv" title="A"><h3 class="title">A</h3><dl><dt><a id="var-ALLOW_EMPTY"></a>ALLOW_EMPTY</dt><dd><p>
Specifies if an output package should still be produced if it is empty.
By default, BitBake does not produce empty packages.
This default behavior can cause issues when there is an
<a class="link" href="#var-RDEPENDS" title="RDEPENDS"><code class="filename">RDEPENDS</code></a> or
some other runtime hard-requirement on the existence of the package.
</p><p>
Like all package-controlling variables, you must always use them in
conjunction with a package name override.
Here is an example:
</p><pre class="literallayout">
ALLOW_EMPTY_${PN}
</pre><p>
</p></dd><dt><a id="var-AUTHOR"></a>AUTHOR</dt><dd><p>The email address used to contact the original author or authors in
order to send patches, forward bugs, etc.</p></dd><dt><a id="var-AUTOREV"></a>AUTOREV</dt><dd><p>Specifies to use the current (newest) source revision.
This variable is with the <code class="filename"><a class="link" href="#var-SRCREV" title="SRCREV">SRCREV</a></code>
variable.</p></dd></dl></div><div class="glossdiv" title="B"><h3 class="title">B</h3><dl><dt><a id="var-B"></a>B</dt><dd><p>
The directory in which the OpenEmbedded build system places
generated objects during a recipe's build process.
By default, this directory is the same as the <a class="link" href="#var-S" title="S"><code class="filename">S</code></a>
directory:
</p><pre class="literallayout">
B = ${WORKDIR}/${BPN}-{PV}/
</pre><p>
You can separate the source directory (<code class="filename">S</code>) and the directory pointed to
by the <code class="filename">B</code> variable.
Most autotools-based recipes support separating these directories.
The build system defaults to using separate directories for <code class="filename">gcc</code>
and some kernel recipes.
</p></dd><dt><a id="var-BAD_RECOMMENDATIONS"></a>BAD_RECOMMENDATIONS</dt><dd><p>
A list of packages not to install despite being recommended by a recipe.
Support for this variable exists only for images that use the
<code class="filename">ipkg</code> packaging system.
</p></dd><dt><a id="var-BBCLASSEXTEND"></a>BBCLASSEXTEND</dt><dd><p>
Allows you to extend a recipe so that it builds variants of the software.
Common variants for recipes exist such as "natives" like <code class="filename">quilt-native</code>,
which is a copy of quilt built to run on the build system;
"crosses" such as <code class="filename">gcc-cross</code>,
which is a compiler built to run on the build machine but produces binaries
that run on the target <a class="link" href="#var-MACHINE" title="MACHINE"><code class="filename">MACHINE</code></a>;
"nativesdk", which targets the SDK machine instead of <code class="filename">MACHINE</code>;
and "mulitlibs" in the form "<code class="filename">multilib:&lt;multilib_name&gt;</code>".
</p><p>
To build a different variant of the recipe with a minimal amount of code, it usually
is as simple as adding the following to your recipe:
</p><pre class="literallayout">
BBCLASSEXTEND =+ "native nativesdk"
BBCLASSEXTEND =+ "multilib:&lt;multilib_name&gt;"
</pre><p>
</p></dd><dt><a id="var-BBMASK"></a>BBMASK</dt><dd><p>Prevents BitBake from processing recipes and recipe append files.
You can use the <code class="filename">BBMASK</code> variable to "hide"
these <code class="filename">.bb</code> and <code class="filename">.bbappend</code> files.
BitBake ignores any recipe or recipe append files that match the expression.
It is as if BitBake does not see them at all.
Consequently, matching files are not parsed or otherwise used by
BitBake.</p><p>The value you provide is passed to python's regular expression compiler.
For complete syntax information, see python's documentation at
<a class="ulink" href="http://docs.python.org/release/2.3/lib/re-syntax.html" target="_top">http://docs.python.org/release/2.3/lib/re-syntax.html</a>.
The expression is compared against the full paths to the files.
For example, the following uses a complete regular expression to tell
BitBake to ignore all recipe and recipe append files in the
<code class="filename">.*/meta-ti/recipes-misc/</code> directory:
</p><pre class="literallayout">
BBMASK = ".*/meta-ti/recipes-misc/"
</pre><p>Use the <code class="filename">BBMASK</code> variable from within the
<code class="filename">conf/local.conf</code> file found
in the <a class="link" href="#build-directory" target="_top">build directory</a>.</p></dd><dt><a id="var-BB_NUMBER_THREADS"></a>BB_NUMBER_THREADS</dt><dd><p>The maximum number of tasks BitBake should run in parallel at any one time.
If your host development system supports multiple cores a good rule of thumb
is to set this variable to twice the number of cores.</p></dd><dt><a id="var-BBFILE_COLLECTIONS"></a>BBFILE_COLLECTIONS</dt><dd><p>Lists the names of configured layers.
These names are used to find the other <code class="filename">BBFILE_*</code>
variables.
Typically, each layer will append its name to this variable in its
<code class="filename">conf/layer.conf</code> file.
</p></dd><dt><a id="var-BBFILE_PATTERN"></a>BBFILE_PATTERN</dt><dd><p>Variable that expands to match files from <code class="filename">BBFILES</code> in a particular layer.
This variable is used in the <code class="filename">conf/layer.conf</code> file and must
be suffixed with the name of the specific layer (e.g.
<code class="filename">BBFILE_PATTERN_emenlow</code>).</p></dd><dt><a id="var-BBFILE_PRIORITY"></a>BBFILE_PRIORITY</dt><dd><p>Assigns the priority for recipe files in each layer.</p><p>This variable is useful in situations where the same package appears in
more than one layer.
Setting this variable allows you to prioritize a
layer against other layers that contain the same package - effectively
letting you control the precedence for the multiple layers.
The precedence established through this variable stands regardless of a
layer's package version (<code class="filename">PV</code> variable).
For example, a layer that has a package with a higher <code class="filename">PV</code> value but for
which the <code class="filename">BBFILE_PRIORITY</code> is set to have a lower precedence still has a
lower precedence.</p><p>A larger value for the <code class="filename">BBFILE_PRIORITY</code> variable results in a higher
precedence.
For example, the value 6 has a higher precedence than the value 5.
If not specified, the <code class="filename">BBFILE_PRIORITY</code> variable is set based on layer
dependencies (see the
<code class="filename"><a class="link" href="#var-LAYERDEPENDS" title="LAYERDEPENDS">LAYERDEPENDS</a></code> variable for
more information.
The default priority, if unspecified
for a layer with no dependencies, is the lowest defined priority + 1
(or 1 if no priorities are defined).</p><div class="tip" title="Tip" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Tip</h3>
You can use the command <code class="filename">bitbake-layers show_layers</code> to list
all configured layers along with their priorities.
</div></dd><dt><a id="var-BBFILES"></a>BBFILES</dt><dd><p>List of recipe files used by BitBake to build software</p></dd><dt><a id="var-BBPATH"></a>BBPATH</dt><dd><p>Used by BitBake to locate <code class="filename">.bbclass</code> and configuration files.
This variable is analogous to the <code class="filename">PATH</code> variable.</p></dd><dt><a id="var-BBINCLUDELOGS"></a>BBINCLUDELOGS</dt><dd><p>Variable that controls how BitBake displays logs on build failure.</p></dd><dt><a id="var-BBLAYERS"></a>BBLAYERS</dt><dd><p>Lists the layers to enable during the build.
This variable is defined in the <code class="filename">bblayers.conf</code> configuration
file in the <a class="link" href="#build-directory" target="_top">build directory</a>.
Here is an example:
</p><pre class="literallayout">
BBLAYERS = " \
/home/scottrif/poky/meta \
/home/scottrif/poky/meta-yocto \
/home/scottrif/poky/meta-mykernel \
"
</pre><p>
This example enables three layers, one of which is a custom, user-defined layer
named <code class="filename">meta-mykernel</code>.
</p></dd><dt><a id="var-BPN"></a>BPN</dt><dd><p>Bare name of package with any suffixes like -cross -native removed.</p></dd></dl></div><div class="glossdiv" title="C"><h3 class="title">C</h3><dl><dt><a id="var-CFLAGS"></a>CFLAGS</dt><dd><p>
Flags passed to C compiler for the target system.
This variable evaluates to the same as
<code class="filename"><a class="link" href="#var-TARGET_CFLAGS" title="TARGET_CFLAGS">TARGET_CFLAGS</a></code>.
</p></dd><dt><a id="var-COMPATIBLE_MACHINE"></a>COMPATIBLE_MACHINE</dt><dd><p>A regular expression which evaluates to match the machines the recipe
works with.
It stops recipes being run on machines for which they are not compatible.
This is particularly useful with kernels.
It also helps to increase parsing speed as further parsing of the recipe is skipped
if it is found the current machine is not compatible.</p></dd><dt><a id="var-CONFFILES"></a>CONFFILES</dt><dd><p>
Identifies editable or configurable files that are part of a package.
If the Package Management System (PMS) is being used to update
packages on the target system, it is possible that
configuration files you have changed after the original installation
and that you now want to remain unchanged are overwritten.
In other words, editable files might exist in the package that you do not
want reset as part of the package update process.
You can use the <code class="filename">CONFFILES</code> variable to list the files in the
package that you wish to prevent the PMS from overwriting during this update process.
</p><p>
To use the <code class="filename">CONFFILES</code> variable, provide a package name
override that identifies the package.
Then, provide a space-separated list of files.
Here is an example:
</p><pre class="literallayout">
CONFFILES_${PN} += "${sysconfdir}/file1 \
${sysconfdir}/file2 ${sysconfdir}/file3"
</pre><p>
</p><p>
A relationship exists between the <code class="filename">CONFFILES</code> and
<code class="filename"><a class="link" href="#var-FILES" title="FILES">FILES</a></code> variables.
The files listed within <code class="filename">CONFFILES</code> must be a subset of
the files listed within <code class="filename">FILES</code>.
Because the configuration files you provide with <code class="filename">CONFFILES</code>
are simply being identified so that the PMS will not overwrite them,
it makes sense that
the files must already be included as part of the package through the
<code class="filename">FILES</code> variable.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
When specifying paths as part of the <code class="filename">CONFFILES</code> variable,
it is good practice to use appropriate path variables.
For example, <code class="filename">${sysconfdir}</code> rather than
<code class="filename">/etc</code> or <code class="filename">${bindir}</code> rather
than <code class="filename">/usr/bin</code>.
You can find a list of these variables at the top of the
<code class="filename">/meta/conf/bitbake.conf</code> file in the
<a class="link" href="#source-directory" target="_top">source directory</a>.
</div></dd><dt><a id="var-CONFIG_SITE"></a>CONFIG_SITE</dt><dd><p>
A list of files that contains <code class="filename">autoconf</code> test results relevant
to the current build.
This variable is used by the Autotools utilities when running
<code class="filename">configure</code>.
</p></dd><dt><a id="var-CORE_IMAGE_EXTRA_INSTALL"></a>CORE_IMAGE_EXTRA_INSTALL</dt><dd><p>
Specifies the list of packages to be added to the image.
This variable should only be set in the <code class="filename">local.conf</code>
configuration file found in the
<a class="link" href="#build-directory" target="_top">build directory</a>.
</p><p>
This variable replaces <code class="filename">POKY_EXTRA_INSTALL</code>, which is no longer supported.
</p></dd></dl></div><div class="glossdiv" title="D"><h3 class="title">D</h3><dl><dt><a id="var-D"></a>D</dt><dd><p>The destination directory.</p></dd><dt><a id="var-DEBUG_BUILD"></a>DEBUG_BUILD</dt><dd><p>
Specifies to build packages with debugging information.
This influences the value of the
<code class="filename"><a class="link" href="#var-SELECTED_OPTIMIZATION" title="SELECTED_OPTIMIZATION">SELECTED_OPTIMIZATION</a></code>
variable.
</p></dd><dt><a id="var-DEBUG_OPTIMIZATION"></a>DEBUG_OPTIMIZATION</dt><dd><p>
The options to pass in
<code class="filename"><a class="link" href="#var-TARGET_CFLAGS" title="TARGET_CFLAGS">TARGET_CFLAGS</a></code>
and <code class="filename"><a class="link" href="#var-CFLAGS" title="CFLAGS">CFLAGS</a></code> when compiling
a system for debugging.
This variable defaults to "-O -fno-omit-frame-pointer -g".
</p></dd><dt><a id="var-DEFAULT_PREFERENCE"></a>DEFAULT_PREFERENCE</dt><dd><p>Specifies the priority of recipes.</p></dd><dt><a id="var-DEPENDS"></a>DEPENDS</dt><dd><p>
A list of build-time dependencies for a given recipe.
The variable indicates recipes that must have been staged before a
particular recipe can configure.
</p></dd><dt><a id="var-DESCRIPTION"></a>DESCRIPTION</dt><dd><p>The package description used by package managers.</p></dd><dt><a id="var-DESTDIR"></a>DESTDIR</dt><dd><p>the destination directory.</p></dd><dt><a id="var-DISTRO"></a>DISTRO</dt><dd><p>The short name of the distribution.</p></dd><dt><a id="var-DISTRO_EXTRA_RRECOMMENDS"></a>DISTRO_EXTRA_RRECOMMENDS</dt><dd><p></p><p>The list of packages which extend usability of the image.
Those packages will automatically be installed but can be removed by user.</p></dd><dt><a id="var-DISTRO_FEATURES"></a>DISTRO_FEATURES</dt><dd><p>The features of the distribution.</p></dd><dt><a id="var-DISTRO_NAME"></a>DISTRO_NAME</dt><dd><p>The long name of the distribution.</p></dd><dt><a id="var-DISTRO_PN_ALIAS"></a>DISTRO_PN_ALIAS</dt><dd><p>Alias names used for the recipe in various Linux distributions.</p><p>See the
"<a class="link" href="#usingpoky-configuring-DISTRO_PN_ALIAS" target="_top">Handling
a Package Name Alias</a>" section in the Yocto Project Development
Manual for more information.</p></dd><dt><a id="var-DISTRO_VERSION"></a>DISTRO_VERSION</dt><dd><p>the version of the distribution.</p></dd><dt><a id="var-DL_DIR"></a>DL_DIR</dt><dd><p>
The central download directory used by the build process to store downloads.
You can set this directory by defining the <code class="filename">DL_DIR</code>
variable in the <code class="filename">/conf/local.conf</code> file.
This directory is self-maintaining and you should not have
to touch it.
By default, the directory is <code class="filename">downloads</code> in the
<a class="link" href="#build-directory" target="_top">build directory</a>.
</p><pre class="literallayout">
#DL_DIR ?= "${TOPDIR}/downloads"
</pre><p>
To specify a different download directory, simply uncomment the line
and provide your directory.
</p><p>
During a first build, the system downloads many different source code
tarballs from various upstream projects.
Downloading can take a while, particularly if your network
connection is slow.
Tarballs are all stored in the directory defined by
<code class="filename">DL_DIR</code> and the build system looks there first
to find source tarballs.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
When wiping and rebuilding, you can preserve this directory to speed
up this part of subsequent builds.
</div><p>
</p><p>
You can safely share this directory between multiple builds on the
same development machine.
For additional information on how the build process gets source files
when working behind a firewall or proxy server, see the
"<a class="link" href="#how-does-the-yocto-project-obtain-source-code-and-will-it-work-behind-my-firewall-or-proxy-server">FAQ</a>"
chapter.
</p></dd></dl></div><div class="glossdiv" title="E"><h3 class="title">E</h3><dl><dt><a id="var-ENABLE_BINARY_LOCALE_GENERATION"></a>ENABLE_BINARY_LOCALE_GENERATION</dt><dd><p></p><p>Variable that controls which locales for <code class="filename">eglibc</code> are
to be generated during the build (useful if the target device has 64Mbytes
of RAM or less).</p></dd><dt><a id="var-EXTRA_IMAGE_FEATURES"></a>EXTRA_IMAGE_FEATURES</dt><dd><p>Allows extra packages to be added to the generated images.
You set this variable in the <code class="filename">local.conf</code>
configuration file.
Note that some image features are also added using the
<code class="filename"><a class="link" href="#var-IMAGE_FEATURES" title="IMAGE_FEATURES">IMAGE_FEATURES</a></code>
variable generally configured in image recipes.
You can use this variable to add more features in addition to those.
Here are some examples of features you can add:</p><pre class="literallayout">
"dbg-pkgs" - Adds -dbg packages for all installed packages
including symbol information for debugging and
profiling.
"dev-pkgs" - Adds -dev packages for all installed packages.
This is useful if you want to develop against
the libraries in the image.
"tools-sdk" - Adds development tools such as gcc, make,
pkgconfig and so forth.
"tools-debug" - Adds debugging tools such as gdb and
strace.
"tools-profile" - Adds profiling tools such as oprofile,
exmap, lttng and valgrind (x86 only).
"tools-testapps" - Adds useful testing tools such as
ts_print, aplay, arecord and so
forth.
"debug-tweaks" - Makes an image suitable for development.
For example, ssh root access has a blank
password. You should remove this feature
before you produce a production image.
There are other application targets too, see
<code class="filename">meta/classes/poky-image.bbclass</code>
and <code class="filename">meta/packages/tasks/task-poky.bb</code>
for more details.
</pre></dd><dt><a id="var-EXTRA_IMAGEDEPENDS"></a>EXTRA_IMAGEDEPENDS</dt><dd><p>A list of recipes to be built that do not provide packages to be installed in
the root filesystem.
</p><p>Sometimes a recipe is required to build the final image but is not
needed in the root filesystem.
You can use the <code class="filename">EXTRA_IMAGEDEPENDS</code> variable to
list these recipes and thus, specify the dependencies.
A typical example is a required bootloader in a machine configuration.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
To add packages to the root filesystem, see the various
<code class="filename">*DEPENDS</code> and <code class="filename">*RECOMMENDS</code>
variables.
</div></dd><dt><a id="var-EXTRA_OECMAKE"></a>EXTRA_OECMAKE</dt><dd><p>Additional <code class="filename">cmake</code> options.</p></dd><dt><a id="var-EXTRA_OECONF"></a>EXTRA_OECONF</dt><dd><p>Additional <code class="filename">configure</code> script options.</p></dd><dt><a id="var-EXTRA_OEMAKE"></a>EXTRA_OEMAKE</dt><dd><p>Additional GNU <code class="filename">make</code> options.</p></dd></dl></div><div class="glossdiv" title="F"><h3 class="title">F</h3><dl><dt><a id="var-FILES"></a>FILES</dt><dd><p>
The list of directories or files that are placed in packages.
</p><p>
To use the <code class="filename">FILES</code> variable, provide a package name
override that identifies the package.
Then, provide a space-separated list of files or paths that identifies the
files you want included as part of the package.
Here is an example:
</p><pre class="literallayout">
FILES_${PN} += "${bindir}/mydir1/ ${bindir}/mydir2/myfile"
</pre><p>
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
When specifying paths as part of the <code class="filename">FILES</code> variable,
it is good practice to use appropriate path variables.
For example, <code class="filename">${sysconfdir}</code> rather than
<code class="filename">/etc</code> or <code class="filename">${bindir}</code> rather
than <code class="filename">/usr/bin</code>.
You can find a list of these variables at the top of the
<code class="filename">/meta/conf/bitbake.conf</code> file in the
<a class="link" href="#source-directory" target="_top">source directory</a>.
</div><p>
If some of the files you provide with the <code class="filename">FILES</code> variable
are editable and you know they should not be
overwritten during the package update process by the Package Management
System (PMS), you can identify these files so that the PMS will not
overwrite them.
See the <code class="filename"><a class="link" href="#var-CONFFILES" title="CONFFILES">CONFFILES</a></code>
variable for information on how to identify these files to the PMS.
</p></dd><dt><a id="var-FILESEXTRAPATHS"></a>FILESEXTRAPATHS</dt><dd><p>
Extends the search path the OpenEmbedded build system uses when
looking for files and patches as it processes recipes.
The directories BitBake uses when it processes recipes is defined by the
<a class="link" href="#var-FILESPATH" title="FILESPATH"><code class="filename">FILESPATH</code></a> variable.
You can add directories to the search path by defining the
<code class="filename">FILESEXTRAPATHS</code> variable.
</p><p>
To add paths to the search order, provide a list of directories and separate
each path using a colon character as follows:
</p><pre class="literallayout">
FILESEXTRAPATHS_prepend := "path_1:path_2:path_3:"
</pre><p>
Typically, you want your directories search first.
To make sure that happens, use <code class="filename">_prepend</code> and
the immediate expansion (<code class="filename">:=</code>) operator as shown in the
previous example.
Finally, to maintain the integrity of the <code class="filename">FILESPATH</code> variable,
you must include the appropriate beginning or ending (as needed) colon character.
</p><p>
The <code class="filename">FILESEXTRAPATHS</code> variable is intended for use in
<code class="filename">.bbappend</code> files to include any additional files provided in that layer.
You typically accomplish this with the following:
</p><pre class="literallayout">
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
</pre><p>
</p></dd><dt><a id="var-FILESPATH"></a>FILESPATH</dt><dd><p>
The default set of directories the OpenEmbedded build system uses
when searching for patches and files.
During the build process, BitBake searches each directory in
<code class="filename">FILESPATH</code> in the specified order when looking for
files and patches specified by each <code class="filename">file://</code> URI in a recipe.
</p><p>
The default value for the <code class="filename">FILESPATH</code> variable is defined
in the <code class="filename">base.bbclass</code> class found in
<code class="filename">meta/classes</code> in the
<a class="link" href="#source-directory" target="_top">source directory</a>:
</p><pre class="literallayout">
FILESPATH = "${@base_set_filespath([ "${FILE_DIRNAME}/${PF}", \
"${FILE_DIRNAME}/${P}", "${FILE_DIRNAME}/${PN}", \
"${FILE_DIRNAME}/${BP}", "${FILE_DIRNAME}/${BPN}", \
"${FILE_DIRNAME}/files", "${FILE_DIRNAME}" ], d)}"
</pre><p>
Do not hand-edit the <code class="filename">FILESPATH</code> variable.
If you want to extend the set of pathnames that BitBake uses when searching for
files and patches, use the
<a class="link" href="#var-FILESEXTRAPATHS" title="FILESEXTRAPATHS"><code class="filename">FILESEXTRAPATHS</code></a> variable.
</p></dd><dt><a id="var-FILESYSTEM_PERMS_TABLES"></a>FILESYSTEM_PERMS_TABLES</dt><dd><p>Allows you to define your own file permissions settings table as part of
your configuration for the packaging process.
For example, suppose you need a consistent set of custom permissions for
a set of groups and users across an entire work project.
It is best to do this in the packages themselves but this is not always
possible.
</p><p>
By default, the OpenEmbedded build system uses the <code class="filename">fs-perms.txt</code>, which
is located in the <code class="filename">meta/files</code> folder in the
<a class="link" href="#source-directory" target="_top">source directory</a>.
If you create your own file permissions setting table, you should place it in your
layer or the distros layer.
</p><p>
You define the <code class="filename">FILESYSTEM_PERMS_TABLES</code> variable in the
<code class="filename">conf/local.conf</code> file, which is found in the
<a class="link" href="#build-directory" target="_top">build directory</a>, to
point to your custom <code class="filename">fs-perms.txt</code>.
You can specify more than a single file permissions setting table.
The paths you specify to these files must be defined within the
<code class="filename">BBPATH</code> variable.
</p><p>
For guidance on how to create your own file permissions settings table file,
examine the existing <code class="filename">fs-perms.txt</code>.
</p></dd><dt><a id="var-FULL_OPTIMIZATION"></a>FULL_OPTIMIZATION</dt><dd><p>
The options to pass in
<code class="filename"><a class="link" href="#var-TARGET_CFLAGS" title="TARGET_CFLAGS">TARGET_CFLAGS</a></code>
and <code class="filename"><a class="link" href="#var-CFLAGS" title="CFLAGS">CFLAGS</a></code>
when compiling an optimized system.
This variable defaults to
"-fexpensive-optimizations -fomit-frame-pointer -frename-registers -O2".
</p></dd></dl></div><div class="glossdiv" title="H"><h3 class="title">H</h3><dl><dt><a id="var-HOMEPAGE"></a>HOMEPAGE</dt><dd><p>Website where more info about package can be found</p></dd></dl></div><div class="glossdiv" title="I"><h3 class="title">I</h3><dl><dt><a id="var-IMAGE_FEATURES"></a>IMAGE_FEATURES</dt><dd><p>The list of features present in images.
Typically, you configure this variable in image recipes.
Note that you can add extra features to the image by using the
<code class="filename"><a class="link" href="#var-EXTRA_IMAGE_FEATURES" title="EXTRA_IMAGE_FEATURES">EXTRA_IMAGE_FEATURES</a></code> variable.
See the "<a class="link" href="#ref-features-image" title="8.3. Reference: Images">Images</a>" chapter for the
list of features present in images built by the OpenEmbedded build system.</p></dd><dt><a id="var-IMAGE_FSTYPES"></a>IMAGE_FSTYPES</dt><dd><p>Formats of root filesystem images that you want to have created.</p></dd><dt><a id="var-IMAGE_INSTALL"></a>IMAGE_INSTALL</dt><dd><p>
Specifies the packages to install into an image.
The <code class="filename">IMAGE_INSTALL</code> variable is a mechanism for an image
recipe and you should use it with care to avoid ordering issues.
</p><p>
Image recipes set <code class="filename">IMAGE_INSTALL</code> to specify the
packages to install into an image through <code class="filename">image.bbclass</code>.
Additionally, "helper" classes exist, such as <code class="filename">core-image.bbclass</code>,
that can take
<code class="filename"><a class="link" href="#var-IMAGE_FEATURES" title="IMAGE_FEATURES">IMAGE_FEATURES</a></code> lists
and turn these into auto-generated entries in
<code class="filename">IMAGE_INSTALL</code> in addition to its default contents.
</p><p>
Using <code class="filename">IMAGE_INSTALL</code> with the <code class="filename">+=</code>
operator from the <code class="filename">/conf/local.conf</code> file or from within
an image recipe is not recommended as it can cause ordering issues.
Since <code class="filename">core-image.bbclass</code> sets <code class="filename">IMAGE_INSTALL</code>
to a default value using the <code class="filename">?=</code> operator, using a
<code class="filename">+=</code> operation against <code class="filename">IMAGE_INSTALL</code>
will result in unexpected behavior when used in
<code class="filename">/conf/local.conf</code>.
Furthermore, the same operation from with an image recipe may or may not
succeed depending on the specific situation.
In both these cases, the behavior is contrary to how most users expect
the <code class="filename">+=</code> operator to work.
</p><p>
When you use this variable, it is best to use it as follows:
</p><pre class="literallayout">
IMAGE_INSTALL_append = " package-name"
</pre><p>
Be sure to include the space between the quotation character and the start of the
package name.
</p></dd><dt><a id="var-IMAGE_OVERHEAD_FACTOR"></a>IMAGE_OVERHEAD_FACTOR</dt><dd><p>
Defines a multiplier that the build system applies to the initial image
size for cases when the multiplier times the returned disk usage value
for the image is greater than the sum of
<code class="filename"><a class="link" href="#var-IMAGE_ROOTFS_SIZE" title="IMAGE_ROOTFS_SIZE">IMAGE_ROOTFS_SIZE</a></code>
and
<code class="filename"><a class="link" href="#var-IMAGE_ROOTFS_EXTRA_SPACE" title="IMAGE_ROOTFS_EXTRA_SPACE">IMAGE_ROOTFS_EXTRA_SPACE</a></code>.
The result of the multiplier applied to the initial image size creates
free disk space in the image as overhead.
By default, the build process uses a multiplier of 1.3 for this variable.
This default value results in 30% free disk space added to the image when this
method is used to determine the final generated image size.
You should be aware that post install scripts and the package management
system uses disk space inside this overhead area.
Consequently, the multiplier does not produce an image with
all the theoretical free disk space.
See <code class="filename"><a class="link" href="#var-IMAGE_ROOTFS_SIZE" title="IMAGE_ROOTFS_SIZE">IMAGE_ROOTFS_SIZE</a></code>
for information on how the build system determines the overall image size.
</p><p>
The default 30% free disk space typically gives the image enough room to boot
and allows for basic post installs while still leaving a small amount of
free disk space.
If 30% free space is inadequate, you can increase the default value.
For example, the following setting gives you 50% free space added to the image:
</p><pre class="literallayout">
IMAGE_OVERHEAD_FACTOR = "1.5"
</pre><p>
</p><p>
Alternatively, you can ensure a specific amount of free disk space is added
to the image by using
<code class="filename"><a class="link" href="#var-IMAGE_ROOTFS_EXTRA_SPACE" title="IMAGE_ROOTFS_EXTRA_SPACE">IMAGE_ROOTFS_EXTRA_SPACE</a></code>
the variable.
</p></dd><dt><a id="var-IMAGE_ROOTFS_EXTRA_SPACE"></a>IMAGE_ROOTFS_EXTRA_SPACE</dt><dd><p>
Defines additional free disk space created in the image in Kbytes.
By default, this variable is set to "0".
This free disk space is added to the image after the build system determines
the image size as described in
<code class="filename"><a class="link" href="#var-IMAGE_ROOTFS_SIZE" title="IMAGE_ROOTFS_SIZE">IMAGE_ROOTFS_SIZE</a></code>.
</p><p>
This variable is particularly useful when you want to ensure that a
specific amount of free disk space is available on a device after an image
is installed and running.
For example, to be sure 5 Gbytes of free disk space is available, set the
variable as follows:
</p><pre class="literallayout">
IMAGE_ROOTFS_EXTRA_SPACE = "5242880"
</pre><p>
</p></dd><dt><a id="var-IMAGE_ROOTFS_SIZE"></a>IMAGE_ROOTFS_SIZE</dt><dd><p>
Defines the size in Kbytes for the generated image.
The OpenEmbedded build system determines the final size for the generated
image using an algorithm that takes into account the initial disk space used
for the generated image, a requested size for the image, and requested
additional free disk space to be added to the image.
Programatically, the build system determines the final size of the
generated image as follows:
</p><pre class="literallayout">
if (image-du * overhead) &lt; rootfs-size:
internal-rootfs-size = rootfs-size + xspace
else:
internal-rootfs-size = (image-du * overhead) + xspace
where:
image-du = Returned value of the du command on
the image.
overhead = IMAGE_OVERHEAD_FACTOR
rootfs-size = IMAGE_ROOTFS_SIZE
internal-rootfs-size = Initial root filesystem
size before any modifications.
xspace = IMAGE_ROOTFS_EXTRA_SPACE
</pre><p>
</p></dd><dt><a id="var-INC_PR"></a>INC_PR</dt><dd><p>Defines the Package revision.
You manually combine values for <code class="filename">INC_PR</code> into the
<a class="link" href="#var-PR" title="PR"><code class="filename">PR</code></a> field of the parent recipe.
When you change this variable, you change the <code class="filename">PR</code>
value for every person that includes the file.</p><p>
The following example shows how to use the <code class="filename">INC_PR</code> variable
given a common <code class="filename">.inc</code> file that defines the variable.
Once defined, you can use the variable to set the
<code class="filename">PR</code> value:
</p><pre class="literallayout">
recipes-graphics/xorg-font/encodings_1.0.4.bb:PR = "${INC_PR}.1"
recipes-graphics/xorg-font/font-util_1.3.0.bb:PR = "${INC_PR}.0"
recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
recipes-graphics/xorg-font/xorg-font-common.inc:INC_PR = "r2"
</pre></dd><dt><a id="var-INHIBIT_PACKAGE_STRIP"></a>INHIBIT_PACKAGE_STRIP</dt><dd><p>
Causes the build to not strip binaries in resulting packages.
</p></dd><dt><a id="var-INHERIT"></a>INHERIT</dt><dd><p>
Causes the named class to be inherited at
this point during parsing.
The variable is only valid in configuration files.
</p></dd><dt><a id="var-INITSCRIPT_PACKAGES"></a>INITSCRIPT_PACKAGES</dt><dd><p>
A list of the packages that contain initscripts.
If multiple packages are specified, you need to append the package name
to the other <code class="filename">INITSCRIPT_*</code> as an override.</p><p>
This variable is used in recipes when using <code class="filename">update-rc.d.bbclass</code>.
The variable is optional and defaults to the <code class="filename">PN</code> variable.
</p></dd><dt><a id="var-INITSCRIPT_NAME"></a>INITSCRIPT_NAME</dt><dd><p>
The filename of the initscript (as installed to <code class="filename">${etcdir}/init.d)</code>.
</p><p>
This variable is used in recipes when using <code class="filename">update-rc.d.bbclass</code>.
The variable is Mandatory.
</p></dd><dt><a id="var-INITSCRIPT_PARAMS"></a>INITSCRIPT_PARAMS</dt><dd><p>
Specifies the options to pass to <code class="filename">update-rc.d</code>.
An example is <code class="filename">start 99 5 2 . stop 20 0 1 6 .</code>, which gives the script a
runlevel of 99, starts the script in initlevels 2 and 5, and
stops the script in levels 0, 1 and 6.
</p><p>
The variable is mandatory and is used in recipes when using
<code class="filename">update-rc.d.bbclass</code>.
</p></dd></dl></div><div class="glossdiv" title="K"><h3 class="title">K</h3><dl><dt><a id="var-KBRANCH"></a>KBRANCH</dt><dd><p>
A regular expression used by the build process to explicitly identify the kernel
branch that is validated, patched and configured during a build.
The <code class="filename">KBRANCH</code> variable is optional.
You can use it to trigger checks to ensure the exact kernel branch you want is
being used by the build process.
</p><p>
Values for this variable are set in the kernel's recipe file and the kernel's
append file.
For example, if you are using the Yocto Project kernel that is based on the
Linux 3.2 kernel, the kernel recipe file is the
<code class="filename">meta/recipes-kernel/linux/linux-yocto_3.2.bb</code> file.
Following is the default value for <code class="filename">KBRANCH</code> and the five overrides
for the architectures the Yocto Project supports:
</p><pre class="literallayout">
KBRANCH = "standard/default/base"
KBRANCH_qemux86 = "standard/default/common-pc/base"
KBRANCH_qemux86-64 = "standard/default/common-pc-64/base"
KBRANCH_qemuppc = "standard/default/qemu-ppc32"
KBRANCH_qemumips = "standard/default/mti-malta32-be"
KBRANCH_qemuarm = "standard/default/arm-versatile-926ejs"
</pre><p>
Each of the above branches exist in the <code class="filename">linux-yocto-3.2</code> kernel Git
repository <a class="ulink" href="http://git.yoctoproject.org/cgit.cgi/linux-yocto-3.2/refs/heads" target="_top">http://git.yoctoproject.org/cgit.cgi/linux-yocto-3.2/refs/heads</a>.
</p><p>
This variable is also used from the kernel's append file to identify the kernel
branch specific to a particular machine or target hardware.
The kernel's append file is located in the BSP layer for a given machine.
For example, the kernel append file for the Crown Bay BSP is in the
<code class="filename">meta-intel</code> Git repository and is named
<code class="filename">meta-crownbay/recipes-kernel/linux/linux-yocto_3.2.bbappend</code>.
Here are the related statements from the append file:
</p><pre class="literallayout">
COMPATIBLE_MACHINE_crownbay = "crownbay"
KMACHINE_crownbay = "crownbay"
KBRANCH_crownbay = "standard/default/crownbay"
COMPATIBLE_MACHINE_crownbay-noemgd = "crownbay-noemgd"
KMACHINE_crownbay-noemgd = "crownbay"
KBRANCH_crownbay-noemgd = "standard/default/crownbay"
</pre><p>
The <code class="filename">KBRANCH_*</code> statements identify the kernel branch to
use when building for the Crown Bay BSP.
In this case there are two identical statements: one for each type of
Crown Bay machine.
</p></dd><dt><a id="var-KERNEL_FEATURES"></a>KERNEL_FEATURES</dt><dd><p>Includes additional metadata from the Yocto Project kernel Git repository.
In the OpenEmbedded build system, the default Board Support Packages (BSPs)
metadata is provided through
the <code class="filename">KMACHINE</code> and <code class="filename">KBRANCH</code> variables.
You can use the <code class="filename">KERNEL_FEATURES</code> variable to further
add metadata for all BSPs.</p><p>The metadata you add through this variable includes config fragments and
features descriptions,
which usually includes patches as well as config fragments.
You typically override the <code class="filename">KERNEL_FEATURES</code> variable
for a specific machine.
In this way, you can provide validated, but optional, sets of kernel
configurations and features.</p><p>For example, the following adds <code class="filename">netfilter</code> to all
the Yocto Project kernels and adds sound support to the <code class="filename">qemux86</code>
machine:
</p><pre class="literallayout">
# Add netfilter to all linux-yocto kernels
KERNEL_FEATURES="features/netfilter"
# Add sound support to the qemux86 machine
KERNEL_FEATURES_append_qemux86="cfg/sound"
</pre></dd><dt><a id="var-KERNEL_IMAGETYPE"></a>KERNEL_IMAGETYPE</dt><dd><p>The type of kernel to build for a device, usually set by the
machine configuration files and defaults to "zImage".
This variable is used
when building the kernel and is passed to <code class="filename">make</code> as the target to
build.</p></dd><dt><a id="var-KMACHINE"></a>KMACHINE</dt><dd><p>
The machine as known by the kernel.
Sometimes the machine name used by the kernel does not match the machine name
used by the OpenEmbedded build system.
For example, the machine name that the OpenEmbedded build system understands as
<code class="filename">qemuarm</code> goes by a different name in the Linux Yocto kernel.
The kernel understands that machine as <code class="filename">arm_versatile926ejs</code>.
For cases like these, the <code class="filename">KMACHINE</code> variable maps the
kernel machine name to the OpenEmbedded build system machine name.
</p><p>
Kernel machine names are initially defined in the
<a class="link" href="#local-kernel-files" target="_top">Yocto Project Kernel</a> in
the <code class="filename">meta/cfg/kernel-cache/bsp/&lt;bsp_name&gt;/&lt;bsp-name&gt;-&lt;kernel-type&gt;.scc</code> file.
For example, in the <code class="filename">linux-yocto-3.4</code> kernel in the
<code class="filename">meta/cfg/kernel-cache/bsp/cedartrail/cedartrail-standard.scc</code> file,
has the following:
</p><pre class="literallayout">
define KMACHINE cedartrail
define KTYPE standard
define KARCH i386
include ktypes/standard
branch cedartrail
include cedartrail.scc
</pre><p>
You can see that the kernel understands the machine name for the Cedar Trail BSP as
<code class="filename">cedartrail</code>.
</p><p>
If you look in the Cedar Trail BSP layer in the <code class="filename">meta-intel</code> source
repository at <code class="filename">meta-cedartrail/recipes-kernel/linux/linux-yocto_3.0.bbappend</code>,
you will find the following statements among others:
</p><pre class="literallayout">
COMPATIBLE_MACHINE_cedartrail = "cedartrail"
KMACHINE_cedartrail = "cedartrail"
KBRANCH_cedartrail = "yocto/standard/cedartrail"
KERNEL_FEATURES_append_cedartrail += "bsp/cedartrail/cedartrail-pvr-merge.scc"
KERNEL_FEATURES_append_cedartrail += "cfg/efi-ext.scc"
COMPATIBLE_MACHINE_cedartrail-nopvr = "cedartrail"
KMACHINE_cedartrail-nopvr = "cedartrail"
KBRANCH_cedartrail-nopvr = "yocto/standard/cedartrail"
KERNEL_FEATURES_append_cedartrail-nopvr += " cfg/smp.scc"
</pre><p>
The <code class="filename">KMACHINE</code> statements in the kernel's append file make sure that
the OpenEmbedded build system and the Yocto Linux kernel understand the same machine
names.
</p><p>
This append file uses two <code class="filename">KMACHINE</code> statements.
The first is not really necessary but does ensure that the machine known to the
OpenEmbedded build system as <code class="filename">cedartrail</code> maps to the machine
in the kernel also known as <code class="filename">cedartrail</code>:
</p><pre class="literallayout">
KMACHINE_cedartrail = "cedartrail"
</pre><p>
</p><p>
The second statement is a good example of why the <code class="filename">KMACHINE</code> variable
is needed.
In this example, the OpenEmbedded build system uses the <code class="filename">cedartrail-nopvr</code>
machine name to refer to the Cedar Trail BSP that does not support the propriatory
PowerVR driver.
The kernel, however, uses the machine name <code class="filename">cedartrail</code>.
Thus, the append file must map the <code class="filename">cedartrail-nopvr</code> machine name to
the kernel's <code class="filename">cedartrail</code> name:
</p><pre class="literallayout">
KMACHINE_cedartrail-nopvr = "cedartrail"
</pre><p>
</p><p>
BSPs that ship with the Yocto Project release provide all mappings between the Yocto
Project kernel machine names and the OpenEmbedded machine names.
Be sure to use the <code class="filename">KMACHINE</code> if you create a BSP and the machine
name you use is different than that used in the kernel.
</p></dd></dl></div><div class="glossdiv" title="L"><h3 class="title">L</h3><dl><dt><a id="var-LAYERDEPENDS"></a>LAYERDEPENDS</dt><dd><p>Lists the layers that this recipe depends upon, separated by spaces.
Optionally, you can specify a specific layer version for a dependency
by adding it to the end of the layer name with a colon, (e.g. "anotherlayer:3"
to be compared against <code class="filename">LAYERVERSION_anotherlayer</code> in this case).
An error will be produced if any dependency is missing or
the version numbers do not match exactly (if specified).
This variable is used in the <code class="filename">conf/layer.conf</code> file
and must be suffixed with the name of the specific layer (e.g.
<code class="filename">LAYERDEPENDS_mylayer</code>).</p></dd><dt><a id="var-LAYERDIR"></a>LAYERDIR</dt><dd><p>When used inside the <code class="filename">layer.conf</code> configuration
file, this variable provides the path of the current layer.
This variable requires immediate expansion
(see the BitBake manual) as lazy expansion can result in
the expansion happening in the wrong directory and therefore
giving the wrong value.</p></dd><dt><a id="var-LAYERVERSION"></a>LAYERVERSION</dt><dd><p>Optionally specifies the version of a layer as a single number.
You can use this within <code class="filename">LAYERDEPENDS</code> for another layer in order to
depend on a specific version of the layer.
This variable is used in the <code class="filename">conf/layer.conf</code> file
and must be suffixed with the name of the specific layer (e.g.
<code class="filename">LAYERVERSION_mylayer</code>).</p></dd><dt><a id="var-LIC_FILES_CHKSUM"></a>LIC_FILES_CHKSUM</dt><dd><p>Checksums of the license text in the recipe source code.</p><p>This variable tracks changes in license text of the source
code files.
If the license text is changed, it will trigger a build
failure, which gives the developer an opportunity to review any
license change.</p><p>
This variable must be defined for all recipes (unless <code class="filename">LICENSE</code>
is set to "CLOSED")</p><p>For more information, see the
<a class="link" href="#usingpoky-configuring-LIC_FILES_CHKSUM" title="3.4.1. Tracking License Changes">
Tracking License Changes</a> section</p></dd><dt><a id="var-LICENSE"></a>LICENSE</dt><dd><p>The list of package source licenses.</p></dd><dt><a id="var-LICENSE_DIR"></a>LICENSE_DIR</dt><dd><p>Path to additional licenses used during the build.
By default, the OpenEmbedded build system uses <code class="filename">COMMON_LICENSE_DIR</code>
to define the directory that holds common license text used during the build.
The <code class="filename">LICENSE_DIR</code> variable allows you to extend that
location to other areas that have additional licenses:
</p><pre class="literallayout">
LICENSE_DIR += "/path/to/additional/common/licenses"
</pre></dd></dl></div><div class="glossdiv" title="M"><h3 class="title">M</h3><dl><dt><a id="var-MACHINE"></a>MACHINE</dt><dd><p>Specifies the target device.</p></dd><dt><a id="var-MACHINE_ESSENTIAL_EXTRA_RDEPENDS"></a>MACHINE_ESSENTIAL_EXTRA_RDEPENDS</dt><dd><p></p><p>
A list of required packages to install as part of the package being
built.
The build process depends on these packages being present.
Furthermore, because this is a "machine essential" variable, the list of
packages are essential for the machine to boot.
The impact of this variable affects images based on <code class="filename">task-core-boot</code>,
including the <code class="filename">core-image-minimal</code> image.
</p><p>
This variable is similar to the
<code class="filename"><a class="link" href="#var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS" title="MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS">MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</a></code>
variable with the exception that the package being built has a build
dependency on the variable's list of packages.
In other words, the image will not build if a file in this list is not found.
</p><p>
For example, suppose you are building a runtime package that depends
on a certain disk driver.
In this case, you would use the following:
</p><pre class="literallayout">
MACHINE_ESSENTIAL_EXTRA_RDEPENDS += "&lt;disk_driver&gt;"
</pre><p>
</p></dd><dt><a id="var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS"></a>MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</dt><dd><p></p><p>
A list of recommended packages to install as part of the package being
built.
The build process does not depend on these packages being present.
Furthermore, because this is a "machine essential" variable, the list of
packages are essential for the machine to boot.
The impact of this variable affects images based on <code class="filename">task-core-boot</code>,
including the <code class="filename">core-image-minimal</code> image.
</p><p>
This variable is similar to the
<code class="filename"><a class="link" href="#var-MACHINE_ESSENTIAL_EXTRA_RDEPENDS" title="MACHINE_ESSENTIAL_EXTRA_RDEPENDS">MACHINE_ESSENTIAL_EXTRA_RDEPENDS</a></code>
variable with the exception that the package being built does not have a build
dependency on the variable's list of packages.
In other words, the image will build if a file in this list is not found.
However, because this is one of the "essential" variables, the resulting image
might not boot on the machine.
Or, if the machine does boot using the image, the machine might not be fully
functional.
</p><p>
Consider an example where you have a custom kernel with a disk driver
built into the kernel itself, rather than using the driver built as a module.
If you include the package that has the driver module as part of
the variable's list, the
build process will not find that package.
However, because these packages are "recommends" packages, the build will
not fail due to the missing package.
Not accounting for any other problems, the custom kernel would still boot the machine.
</p><p>
Some example packages of these machine essentials are flash, screen, keyboard, mouse,
or touchscreen drivers (depending on the machine).
</p><p>
For example, suppose you are building a runtime package that depends
on a mouse driver.
In this case, you would use the following:
</p><pre class="literallayout">
MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS += "&lt;mouse_driver&gt;"
</pre><p>
</p></dd><dt><a id="var-MACHINE_EXTRA_RDEPENDS"></a>MACHINE_EXTRA_RDEPENDS</dt><dd><p>
A list of optional but non-machine essential packages to install as
part of the package being built.
Even though these packages are not essential for the machine to boot,
the build process depends on them being present.
The impact of this variable affects all images based on
<code class="filename">task-base</code>, which does not include the
<code class="filename">core-image-minimal</code> or <code class="filename">core-image-basic</code>
images.
</p><p>
This variable is similar to the
<code class="filename"><a class="link" href="#var-MACHINE_EXTRA_RRECOMMENDS" title="MACHINE_EXTRA_RRECOMMENDS">MACHINE_EXTRA_RRECOMMENDS</a></code>
variable with the exception that the package being built has a build
dependency on the variable's list of packages.
In other words, the image will not build if a file in this list is not found.
</p><p>
An example is a machine that might or might not have a WiFi card.
The package containing the WiFi support is not essential for the
machine to boot the image.
If it is not there, the machine will boot but not be able to use the
WiFi functionality.
However, if you include the package with the WiFi support as part of the
variable's package list, the build
process depends on finding the package.
In this case, you would use the following:
</p><pre class="literallayout">
MACHINE_EXTRA_RDEPENDS += "&lt;wifi_driver&gt;"
</pre><p>
</p></dd><dt><a id="var-MACHINE_EXTRA_RRECOMMENDS"></a>MACHINE_EXTRA_RRECOMMENDS</dt><dd><p></p><p>
A list of optional but non-machine essential packages to install as
part of the package being built.
The package being built has no build dependency on the list of packages
with this variable.
The impact of this variable affects only images based on
<code class="filename">task-base</code>, which does not include the
<code class="filename">core-image-minimal</code> or <code class="filename">core-image-basic</code>
images.
</p><p>
This variable is similar to the
<code class="filename"><a class="link" href="#var-MACHINE_EXTRA_RDEPENDS" title="MACHINE_EXTRA_RDEPENDS">MACHINE_EXTRA_RDEPENDS</a></code>
variable with the exception that the package being built does not have a build
dependency on the variable's list of packages.
In other words, the image will build if a file in this list is not found.
</p><p>
An example is a machine that might or might not have a WiFi card.
The package containing the WiFi support is not essential for the
machine to boot the image.
If it is not there, the machine will boot but not be able to use the
WiFi functionality.
You are free to either include or not include the
the package with the WiFi support as part of the
variable's package list, the build
process does not depend on finding the package.
If you include the package, you would use the following:
</p><pre class="literallayout">
MACHINE_EXTRA_RRECOMMENDS += "&lt;wifi_driver&gt;"
</pre><p>
</p></dd><dt><a id="var-MACHINE_FEATURES"></a>MACHINE_FEATURES</dt><dd><p>Specifies the list of device features.
See the <a class="link" href="#ref-features-machine" title="8.2. Machine">Machine</a> section for
more information.</p></dd><dt><a id="var-MAINTAINER"></a>MAINTAINER</dt><dd><p>The email address of the distribution maintainer.</p></dd></dl></div><div class="glossdiv" title="P"><h3 class="title">P</h3><dl><dt><a id="var-PACKAGE_ARCH"></a>PACKAGE_ARCH</dt><dd><p>The architecture of the resulting package.</p></dd><dt><a id="var-PACKAGE_CLASSES"></a>PACKAGE_CLASSES</dt><dd><p>This variable, which is set in the <code class="filename">local.conf</code> configuration
file found in the <code class="filename">conf</code> folder of the
<a class="link" href="#source-directory" target="_top">source directory</a>,
specifies the package manager to use when packaging data.
You can provide one or more arguments for the variable with the first
argument being the package manager used to create images:
</p><pre class="literallayout">
PACKAGE_CLASSES ?= "package_rpm package_deb package_ipk"
</pre><p>
For information on build performance effects as a result of the
package manager use, see
<a class="link" href="#ref-classes-package" title="6.12. Packaging - package*.bbclass">Packaging - <code class="filename">package*.bbclass</code></a>
in this manual.
</p></dd><dt><a id="var-PACKAGE_EXTRA_ARCHS"></a>PACKAGE_EXTRA_ARCHS</dt><dd><p>Specifies the list of architectures compatible with the device CPU.
This variable is useful when you build for several different devices that use
miscellaneous processors such as XScale and ARM926-EJS).</p></dd><dt><a id="var-PACKAGES"></a>PACKAGES</dt><dd><p>The list of packages to be created from the recipe.
The default value is "${PN}-dbg ${PN} ${PN}-doc ${PN}-dev".</p></dd><dt><a id="var-PARALLEL_MAKE"></a>PARALLEL_MAKE</dt><dd><p>Specifies extra options that are passed to the <code class="filename">make</code> command during the
compile tasks.
This variable is usually in the form <code class="filename">-j 4</code>, where the number
represents the maximum number of parallel threads make can run.
If you development host supports multiple cores a good rule of thumb is to set
this variable to twice the number of cores on the host.</p></dd><dt><a id="var-PN"></a>PN</dt><dd><p>The name of the package.
</p></dd><dt><a id="var-PR"></a>PR</dt><dd><p>The revision of the package.
The default value for this variable is "r0".
</p></dd><dt><a id="var-PV"></a>PV</dt><dd><p>The version of the package.
The version is normally extracted from the recipe name.
For example, if the recipe is named
<code class="filename">expat_2.0.1.bb</code>, then <code class="filename">PV</code>
will be <code class="filename">2.0.1</code>.
<code class="filename">PV</code> is generally not overridden within
a recipe unless it is building an unstable version from a source code repository
(e.g. Git or Subversion).
</p></dd><dt><a id="var-PE"></a>PE</dt><dd><p>
the epoch of the package.
The default value is "0".
The field is used to make upgrades possible when the versioning scheme changes in
some backwards incompatible way.
</p></dd><dt><a id="var-PREFERRED_PROVIDER"></a>PREFERRED_PROVIDER</dt><dd><p>
If multiple recipes provide an item, this variable
determines which recipe should be given preference.
The variable must always be suffixed with the name of the
provided item, and should be set to the
<code class="filename">$PN</code> of the recipe
to which you want to give precedence.
Here is an example:
</p><pre class="literallayout">
PREFERRED_PROVIDER_virtual/xserver = "xserver-xf86"
</pre><p>
</p></dd><dt><a id="var-PREFERRED_VERSION"></a>PREFERRED_VERSION</dt><dd><p>
If there are multiple versions of recipes available, this
variable determines which recipe should be given preference.
The variable must always be suffixed with the <code class="filename">$PN</code>
for which to select, and should be set to the
<code class="filename">$PV</code> to which you want to give precedence.
You can use the "<code class="filename">%</code>" character as a wildcard
to match any number of characters, which can be useful when
specifying versions that contain long revision number that could
potentially change.
Here are two examples:
</p><pre class="literallayout">
PREFERRED_VERSION_python = "2.6.6"
PREFERRED_VERSION_linux-yocto = "3.0+git%"
</pre><p>
</p></dd></dl></div><div class="glossdiv" title="R"><h3 class="title">R</h3><dl><dt><a id="var-RCONFLICTS"></a>RCONFLICTS</dt><dd><p>The list of packages that conflict with this package.
Note that the package will not be installed if the conflicting packages are not
first removed.</p></dd><dt><a id="var-RDEPENDS"></a>RDEPENDS</dt><dd><p>
A list of packages that must be installed as part of a package being built.
The package being built has a runtime dependency on the packages in the
variable's list.
In other words, in order for the package being built to run correctly,
it depends on these listed packages.
If a package in this list cannot be found during the build, the build
will not complete.
</p><p>
Because the <code class="filename">RDEPENDS</code> variable applies to packages
being built, you should
always attach an override to the variable to specify the particular runtime package
that has the dependency.
For example, suppose you are building a development package that depends
on the <code class="filename">perl</code> package.
In this case, you would use the following <code class="filename">RDEPENDS</code>
statement:
</p><pre class="literallayout">
RDEPENDS_${PN}-dev += "perl"
</pre><p>
In the example, the package name (<code class="filename">${PN}-dev</code>) must
appear as it would in the
<code class="filename"><a class="link" href="#var-PACKAGES" title="PACKAGES">PACKAGES</a></code> namespace before any
renaming of the output package by classes like <code class="filename">debian.bbclass</code>.
</p><p>
Some automatic handling occurs around the <code class="filename">RDEPENDS</code>
variable:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><code class="filename">shlibdeps</code></em></span>: If a runtime
package contains a shared library (<code class="filename">.so</code>), the build
processes the library in order to determine other libraries to which it
is dynamically linked.
The build process adds these libraries to <code class="filename">RDEPENDS</code>
to create the runtime package.</p></li><li class="listitem"><p><span class="emphasis"><em><code class="filename">pcdeps</code></em></span>: If the package
ships a <code class="filename">pkg-config</code> information file, the build process
uses this file to add items to the <code class="filename">RDEPENDS</code>
variable to create the runtime packages.
</p></li></ul></div><p>
</p></dd><dt><a id="var-RRECOMMENDS"></a>RRECOMMENDS</dt><dd><p>
A list of packages that extend the usability of a package being
built.
The package being built does not depend on this list of packages in
order to successfully build, but needs them for the extended usability.
To specify runtime dependencies for packages, see the
<code class="filename"><a class="link" href="#var-RDEPENDS" title="RDEPENDS">RDEPENDS</a></code> variable.
</p><p>
The OpenEmbedded build process automatically installs the list of packages
as part of the built package.
However, you can remove them later if you want.
If, during the build, a package from the list cannot be found, the build
process continues without an error.
</p><p>
Because the <code class="filename">RRECOMMENDS</code> variable applies to packages
being built, you should
always attach an override to the variable to specify the particular package
whose usability is being extended.
For example, suppose you are building a development package that is extended
to support wireless functionality.
In this case, you would use the following:
</p><pre class="literallayout">
RRECOMMENDS_${PN}-dev += "&lt;wireless_package_name&gt;"
</pre><p>
In the example, the package name (<code class="filename">${PN}-dev</code>) must
appear as it would in the
<code class="filename"><a class="link" href="#var-PACKAGES" title="PACKAGES">PACKAGES</a></code> namespace before any
renaming of the output package by classes like <code class="filename">debian.bbclass</code>.
</p></dd><dt><a id="var-RREPLACES"></a>RREPLACES</dt><dd><p>The list of packages that are replaced with this package.</p></dd></dl></div><div class="glossdiv" title="S"><h3 class="title">S</h3><dl><dt><a id="var-S"></a>S</dt><dd><p>
The location in the <a class="link" href="#build-directory" target="_top">build directory</a>
where unpacked package source code resides.
This location is within the working directory
(<code class="filename"><a class="link" href="#var-WORKDIR" title="WORKDIR">WORKDIR</a></code>), which
is not static.
The unpacked source location depends on the package name
(<code class="filename"><a class="link" href="#var-PN" title="PN">PN</a></code>) and
package version (<code class="filename"><a class="link" href="#var-PV" title="PV">PV</a></code>) as
follows:
</p><pre class="literallayout">
${WORKDIR}/${PN}-${PV}
</pre><p>
As an example, assume a
<a class="link" href="#source-directory" target="_top">source directory</a> top-level
folder named <code class="filename">poky</code>
and a default <a class="link" href="#build-directory" target="_top">build directory</a>
at <code class="filename">poky/build</code>.
In this case, the working directory the build system uses to build
the <code class="filename">db</code> package is the following:
</p><pre class="literallayout">
~/poky/build/tmp/work/qemux86-poky-linux/db-5.1.19-r3/db-5.1.19
</pre><p>
</p></dd><dt><a id="var-SECTION"></a>SECTION</dt><dd><p>The section where package should be put.
Package managers use this variable.</p></dd><dt><a id="var-SELECTED_OPTIMIZATION"></a>SELECTED_OPTIMIZATION</dt><dd><p>
The variable takes the value of
<code class="filename"><a class="link" href="#var-FULL_OPTIMIZATION" title="FULL_OPTIMIZATION">FULL_OPTIMIZATION</a></code>
unless <code class="filename"><a class="link" href="#var-DEBUG_BUILD" title="DEBUG_BUILD">DEBUG_BUILD</a></code> = "1".
In this case the value of
<code class="filename"><a class="link" href="#var-DEBUG_OPTIMIZATION" title="DEBUG_OPTIMIZATION">DEBUG_OPTIMIZATION</a></code> is used.
</p></dd><dt><a id="var-SERIAL_CONSOLE"></a>SERIAL_CONSOLE</dt><dd><p>The speed and device for the serial port used to attach the serial console.
This variable is given to the kernel as the "console"
parameter and after booting occurs <code class="filename">getty</code> is started on that port
so remote login is possible.</p></dd><dt><a id="var-SSTATE_DIR"></a>SSTATE_DIR</dt><dd><p>The directory for the shared state.</p></dd><dt><a id="var-SITEINFO_ENDIANNESS"></a>SITEINFO_ENDIANNESS</dt><dd><p>
Specifies the endian byte order of the target system.
The variable is either "le" for little-endian or "be" for big-endian.
</p></dd><dt><a id="var-SITEINFO_BITS"></a>SITEINFO_BITS</dt><dd><p>
Specifies the number of bits for the target system CPU.
The variable is either "32" or "64".
</p></dd><dt><a id="var-SRC_URI"></a>SRC_URI</dt><dd><p>The list of source files - local or remote.</p></dd><dt><a id="var-SRC_URI_OVERRIDES_PACKAGE_ARCH"></a>SRC_URI_OVERRIDES_PACKAGE_ARCH</dt><dd><p></p><p>
By default, the OpenEmbedded build system automatically detects whether
<code class="filename"><a class="link" href="#var-SRC_URI" title="SRC_URI">SRC_URI</a></code>
contains files that are machine-specific.
If so, the build system automatically changes
<code class="filename"><a class="link" href="#var-PACKAGE_ARCH" title="PACKAGE_ARCH">PACKAGE_ARCH</a></code>.
Setting this variable to "0" disables this behavior.
</p></dd><dt><a id="var-SRCDATE"></a>SRCDATE</dt><dd><p>
The date of the source code used to build the package.
This variable applies only if the source was fetched from a Source Code Manager (SCM).
</p></dd><dt><a id="var-SRCREV"></a>SRCREV</dt><dd><p>
The revision of the source code used to build the package.
This variable applies to Subversion, Git, Mercurial and Bazaar
only.
Note that if you wish to build a fixed revision and you wish
to avoid performing a query on the remote repository every time
BitBake parses your recipe, you should specify a <code class="filename">SRCREV</code> that is a
full revision identifier and not just a tag.
</p></dd><dt><a id="var-STAGING_KERNEL_DIR"></a>STAGING_KERNEL_DIR</dt><dd><p>
The directory with kernel headers that are required to build out-of-tree
modules.
</p></dd><dt><a id="var-STAMP"></a>STAMP</dt><dd><p>
The directory (usually <code class="filename">TMPDIR/stamps</code>) with timestamps of
executed tasks.
</p></dd><dt><a id="var-SUMMARY"></a>SUMMARY</dt><dd><p>The short (72 characters or less) summary of the binary package for packaging
systems such as <code class="filename">ipkg</code>, <code class="filename">rpm</code> or
<code class="filename">debian</code>.
By default, this variable inherits <code class="filename">DESCRIPTION</code>.</p></dd></dl></div><div class="glossdiv" title="T"><h3 class="title">T</h3><dl><dt><a id="var-TARGET_ARCH"></a>TARGET_ARCH</dt><dd><p>The architecture of the device being built.
While a number of values are possible, the OpenEmbedded build system primarily supports
<code class="filename">arm</code> and <code class="filename">i586</code>.</p></dd><dt><a id="var-TARGET_CFLAGS"></a>TARGET_CFLAGS</dt><dd><p>
Flags passed to the C compiler for the target system.
This variable evaluates to the same as
<code class="filename"><a class="link" href="#var-CFLAGS" title="CFLAGS">CFLAGS</a></code>.
</p></dd><dt><a id="var-TARGET_FPU"></a>TARGET_FPU</dt><dd><p>Specifies the method for handling FPU code.
For FPU-less targets, which include most ARM CPUs, the variable must be
set to "soft".
If not, the kernel emulation gets used, which results in a performance penalty.</p></dd><dt><a id="var-TARGET_OS"></a>TARGET_OS</dt><dd><p>Specifies the target's operating system.
The variable can be set to "linux" for <code class="filename">eglibc</code>-based systems and
to "linux-uclibc" for <code class="filename">uclibc</code>.
For ARM/EABI targets, there are also "linux-gnueabi" and
"linux-uclibc-gnueabi" values possible.</p></dd><dt><a id="var-TCLIBC"></a>TCLIBC</dt><dd><p>
Specifies which variant of the GNU standard C library (<code class="filename">libc</code>)
to use during the build process.
This variable replaces <code class="filename">POKYLIBC</code>, which is no longer
supported.
</p><p>
You can select <code class="filename">eglibc</code> or <code class="filename">uclibc</code>.
</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
This release of the Yocto Project does not support the
<code class="filename">glibc</code> implementation of <code class="filename">libc</code>.
</div><p>
</p></dd><dt><a id="var-TCMODE"></a>TCMODE</dt><dd><p>
The toolchain selector.
This variable replaces <code class="filename">POKYMODE</code>, which is no longer
supported.
</p><p>
The <code class="filename">TCMODE</code> variable selects the external toolchain
built using the OpenEmbedded build system or a few supported combinations of
the upstream GCC or CodeSourcery Labs toolchain.
The variable determines which of the <code class="filename">tcmode-*</code> files in
the <code class="filename">meta/conf/distro/include</code> directory, which is found in the
<a class="link" href="#source-directory" target="_top">source directory</a>,
is used.
</p><p>
By default, <code class="filename">TCMODE</code> is set to "default", which
chooses the <code class="filename">tcmode-default.inc</code> file.
The variable is similar to
<a class="link" href="#var-TCLIBC" title="TCLIBC"><code class="filename">TCLIBC</code></a>, which controls
the variant of the GNU standard C library (<code class="filename">libc</code>)
used during the build process: <code class="filename">eglibc</code> or <code class="filename">uclibc</code>.
</p></dd><dt><a id="var-TMPDIR"></a>TMPDIR</dt><dd><p>
This variable is the temporary directory the OpenEmbedded build system
uses when it does its work building images.
By default, the <code class="filename">TMPDIR</code> variable is named
<code class="filename">tmp</code> within the
<a class="link" href="#build-directory" target="_top">build directory</a>.
</p><p>
If you want to establish this directory in a location other than the
default, you can uncomment the following statement in the
<code class="filename">conf/local.conf</code> file in the
<a class="link" href="#source-directory" target="_top">source directory</a>:
</p><pre class="literallayout">
#TMPDIR = "${TOPDIR}/tmp"
</pre><p>
</p></dd><dt><a id="var-TOPDIR"></a>TOPDIR</dt><dd><p>
This variable is the
<a class="link" href="#build-directory" target="_top">build directory</a>.
BitBake automatically sets this variable.
The OpenEmbedded build system uses the build directory when building images.
</p></dd></dl></div><div class="glossdiv" title="W"><h3 class="title">W</h3><dl><dt><a id="var-WORKDIR"></a>WORKDIR</dt><dd><p>
The pathname of the working directory in which the OpenEmbedded build system
builds packages.
This directory is located within the
<a class="link" href="#var-TMPDIR" title="TMPDIR"><code class="filename">TMPDIR</code></a> directory structure and changes
as different packages are built.
</p><p>
The actual <code class="filename">WORKDIR</code> directory depends on several things:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">The temporary directory - <a class="link" href="#var-TMPDIR" title="TMPDIR"><code class="filename">TMPDIR</code></a></li><li class="listitem">The package architecture - <a class="link" href="#var-PACKAGE_ARCH" title="PACKAGE_ARCH"><code class="filename">PACKAGE_ARCH</code></a></li><li class="listitem">The target machine - <a class="link" href="#var-MACHINE" title="MACHINE"><code class="filename">MACHINE</code></a></li><li class="listitem">The target operating system - <a class="link" href="#var-TARGET_OS" title="TARGET_OS"><code class="filename">TARGET_OS</code></a></li><li class="listitem">The package name - <a class="link" href="#var-PN" title="PN"><code class="filename">PN</code></a></li><li class="listitem">The package version - <a class="link" href="#var-PV" title="PV"><code class="filename">PV</code></a></li><li class="listitem">The package revision - <a class="link" href="#var-PR" title="PR"><code class="filename">PR</code></a></li></ul></div><p>
</p><p>
For packages that are not dependent on a particular machine,
<code class="filename">WORKDIR</code> is defined as follows:
</p><pre class="literallayout">
${TMPDIR}/work/${PACKAGE_ARCH}-poky-${TARGET_OS}/${PN}-${PV}-${PR}
</pre><p>
As an example, assume a
<a class="link" href="#source-directory" target="_top">source directory</a> top-level
folder name <code class="filename">poky</code> and a default
<a class="link" href="#build-directory" target="_top">build directory</a>
at <code class="filename">poky/build</code>.
In this case, the working directory the build system uses to build
the <code class="filename">v86d</code> package is the following:
</p><pre class="literallayout">
~/poky/build/tmp/work/qemux86-poky-linux/v86d-01.9-r0
</pre><p>
</p><p>
For packages that are dependent on a particular machine, <code class="filename">WORKDIR</code>
is defined slightly different:
</p><pre class="literallayout">
${TMPDIR}/work/${MACHINE}-poky-${TARGET_OS}/${PN}-${PV}-${PR}
</pre><p>
As an example, again assume a source directory top-level folder
named <code class="filename">poky</code> and a default build directory
at <code class="filename">poky/build</code>.
In this case, the working directory the build system uses to build
the <code class="filename">acl</code> package, which is dependent on a
MIPS-based device, is the following:
</p><pre class="literallayout">
~/poky/build/tmp/work/mips-poky-linux/acl-2.2.51-r2
</pre><p>
</p></dd></dl></div></div></div>
<div class="chapter" title="Chapter 10. Variable Context"><div class="titlepage"><div><div><h2 class="title"><a id="ref-varlocality"></a>Chapter 10. Variable Context</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#ref-varlocality-configuration">10.1. Configuration</a></span></dt><dd><dl><dt><span class="section"><a href="#ref-varlocality-config-distro">10.1.1. Distribution (Distro)</a></span></dt><dt><span class="section"><a href="#ref-varlocality-config-machine">10.1.2. Machine</a></span></dt><dt><span class="section"><a href="#ref-varlocality-config-local">10.1.3. Local</a></span></dt></dl></dd><dt><span class="section"><a href="#ref-varlocality-recipes">10.2. Recipes</a></span></dt><dd><dl><dt><span class="section"><a href="#ref-varlocality-recipe-required">10.2.1. Required</a></span></dt><dt><span class="section"><a href="#ref-varlocality-recipe-dependencies">10.2.2. Dependencies</a></span></dt><dt><span class="section"><a href="#ref-varlocality-recipe-paths">10.2.3. Paths</a></span></dt><dt><span class="section"><a href="#ref-varlocality-recipe-build">10.2.4. Extra Build Information</a></span></dt></dl></dd></dl></div><p>
While most variables can be used in almost any context such as
<code class="filename">.conf</code>, <code class="filename">.bbclass</code>,
<code class="filename">.inc</code>, and <code class="filename">.bb</code> files,
some variables are often associated with a particular locality or context.
This chapter describes some common associations.
</p><div class="section" title="10.1. Configuration"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-varlocality-configuration"></a>10.1. Configuration</h2></div></div></div><p>
The following subsections provide lists of variables whose context is
configuration: distribution, machine, and local.
</p><div class="section" title="10.1.1. Distribution (Distro)"><div class="titlepage"><div><div><h3 class="title"><a id="ref-varlocality-config-distro"></a>10.1.1. Distribution (Distro)</h3></div></div></div><p>
This section lists variables whose context is the distribution, or distro.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-DISTRO" title="DISTRO">DISTRO</a></code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-DISTRO_NAME" title="DISTRO_NAME">DISTRO_NAME</a></code>
</p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-DISTRO_VERSION" title="DISTRO_VERSION">DISTRO_VERSION</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-MAINTAINER" title="MAINTAINER">MAINTAINER</a></code>
</p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-PACKAGE_CLASSES" title="PACKAGE_CLASSES">PACKAGE_CLASSES</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-TARGET_OS" title="TARGET_OS">TARGET_OS</a></code>
</p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-TARGET_FPU" title="TARGET_FPU">TARGET_FPU</a></code>
</p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-TCMODE" title="TCMODE">TCMODE</a></code>
</p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-TCLIBC" title="TCLIBC">TCLIBC</a></code>
</p></li></ul></div><p>
</p></div><div class="section" title="10.1.2. Machine"><div class="titlepage"><div><div><h3 class="title"><a id="ref-varlocality-config-machine"></a>10.1.2. Machine</h3></div></div></div><p>
This section lists variables whose context is the machine.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-TARGET_ARCH" title="TARGET_ARCH">TARGET_ARCH</a></code>
</p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-SERIAL_CONSOLE" title="SERIAL_CONSOLE">SERIAL_CONSOLE</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-PACKAGE_EXTRA_ARCHS" title="PACKAGE_EXTRA_ARCHS">PACKAGE_EXTRA_ARCHS</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-IMAGE_FSTYPES" title="IMAGE_FSTYPES">IMAGE_FSTYPES</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-MACHINE_FEATURES" title="MACHINE_FEATURES">MACHINE_FEATURES</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-MACHINE_EXTRA_RDEPENDS" title="MACHINE_EXTRA_RDEPENDS">MACHINE_EXTRA_RDEPENDS
</a></code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-MACHINE_EXTRA_RRECOMMENDS" title="MACHINE_EXTRA_RRECOMMENDS">MACHINE_EXTRA_RRECOMMENDS
</a></code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-MACHINE_ESSENTIAL_EXTRA_RDEPENDS" title="MACHINE_ESSENTIAL_EXTRA_RDEPENDS">MACHINE_ESSENTIAL_EXTRA_RDEPENDS
</a></code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS" title="MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS">
MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</a></code></p></li></ul></div><p>
</p></div><div class="section" title="10.1.3. Local"><div class="titlepage"><div><div><h3 class="title"><a id="ref-varlocality-config-local"></a>10.1.3. Local</h3></div></div></div><p>
This section lists variables whose context is the local configuration through the
<code class="filename">local.conf</code> file.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-DISTRO" title="DISTRO">DISTRO</a></code>
</p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-MACHINE" title="MACHINE">MACHINE</a></code>
</p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-DL_DIR" title="DL_DIR">DL_DIR</a></code>
</p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-BBFILES" title="BBFILES">BBFILES</a></code>
</p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-EXTRA_IMAGE_FEATURES" title="EXTRA_IMAGE_FEATURES">EXTRA_IMAGE_FEATURES
</a></code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-PACKAGE_CLASSES" title="PACKAGE_CLASSES">PACKAGE_CLASSES</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-BB_NUMBER_THREADS" title="BB_NUMBER_THREADS">BB_NUMBER_THREADS</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-BBINCLUDELOGS" title="BBINCLUDELOGS">BBINCLUDELOGS</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-ENABLE_BINARY_LOCALE_GENERATION" title="ENABLE_BINARY_LOCALE_GENERATION">
ENABLE_BINARY_LOCALE_GENERATION</a></code></p></li></ul></div><p>
</p></div></div><div class="section" title="10.2. Recipes"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ref-varlocality-recipes"></a>10.2. Recipes</h2></div></div></div><p>
The following subsections provide lists of variables whose context is
recipes: required, dependencies, path, and extra build information.
</p><div class="section" title="10.2.1. Required"><div class="titlepage"><div><div><h3 class="title"><a id="ref-varlocality-recipe-required"></a>10.2.1. Required</h3></div></div></div><p>
This section lists variables that are required for recipes.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-DESCRIPTION" title="DESCRIPTION">DESCRIPTION</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-LICENSE" title="LICENSE">LICENSE</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-LIC_FILES_CHKSUM" title="LIC_FILES_CHKSUM">LIC_FILES_CHKSUM</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-SECTION" title="SECTION">SECTION</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-HOMEPAGE" title="HOMEPAGE">HOMEPAGE</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-AUTHOR" title="AUTHOR">AUTHOR</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-SRC_URI" title="SRC_URI">SRC_URI</a>
</code></p></li></ul></div><p>
</p></div><div class="section" title="10.2.2. Dependencies"><div class="titlepage"><div><div><h3 class="title"><a id="ref-varlocality-recipe-dependencies"></a>10.2.2. Dependencies</h3></div></div></div><p>
This section lists variables that define recipe dependencies.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-DEPENDS" title="DEPENDS">DEPENDS</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-RDEPENDS" title="RDEPENDS">RDEPENDS</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-RRECOMMENDS" title="RRECOMMENDS">RRECOMMENDS</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-RCONFLICTS" title="RCONFLICTS">RCONFLICTS</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-RREPLACES" title="RREPLACES">RREPLACES</a>
</code></p></li></ul></div><p>
</p></div><div class="section" title="10.2.3. Paths"><div class="titlepage"><div><div><h3 class="title"><a id="ref-varlocality-recipe-paths"></a>10.2.3. Paths</h3></div></div></div><p>
This section lists variables that define recipe paths.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-WORKDIR" title="WORKDIR">WORKDIR</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-S" title="S">S</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-FILES" title="FILES">FILES</a>
</code></p></li></ul></div><p>
</p></div><div class="section" title="10.2.4. Extra Build Information"><div class="titlepage"><div><div><h3 class="title"><a id="ref-varlocality-recipe-build"></a>10.2.4. Extra Build Information</h3></div></div></div><p>
This section lists variables that define extra build information for recipes.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename"><a class="link" href="#var-DISTRO_PN_ALIAS" title="DISTRO_PN_ALIAS">DISTRO_PN_ALIAS</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-EXTRA_OECMAKE" title="EXTRA_OECMAKE">EXTRA_OECMAKE</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-EXTRA_OECONF" title="EXTRA_OECONF">EXTRA_OECONF</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-EXTRA_OEMAKE" title="EXTRA_OEMAKE">EXTRA_OEMAKE</a>
</code></p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-PACKAGES" title="PACKAGES">PACKAGES</a></code>
</p></li><li class="listitem"><p><code class="filename"><a class="link" href="#var-DEFAULT_PREFERENCE" title="DEFAULT_PREFERENCE">DEFAULT_PREFERENCE
</a></code></p></li></ul></div><p>
</p></div></div></div>
<div class="chapter" title="Chapter 11. FAQ"><div class="titlepage"><div><div><h2 class="title"><a id="faq"></a>Chapter 11. FAQ</h2></div></div></div><div class="qandaset" title="Frequently Asked Questions"><a id="id1519542"></a><table border="0" width="100%" summary="Q and A Set"><col align="left" width="1%" /><col /><tbody><tr class="question" title="11.1."><td align="left" valign="top"><a id="id1519546"></a><a id="id1519547"></a><p><b>11.1.</b></p></td><td align="left" valign="top"><p>
How does Poky differ from <a class="ulink" href="http://www.openembedded.org" target="_top">OpenEmbedded</a>?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
The term "Poky" is sometimes used to refer to the build system that the
Yocto Project uses.
The build system used in the Yocto project is referred to as the
OpenEmbedded build system because "Poky" was derived from <a class="ulink" href="http://www.openembedded.org" target="_top">OpenEmbedded</a>.
Poky is a stable, smaller subset focused on the mobile environment.
Development in the Yocto Project using Poky is closely tied to OpenEmbedded with
features being merged regularly between the two for mutual benefit.
For a fuller description of the term "Poky", see the
<a class="link" href="#poky" target="_top">poky</a> term in the Yocto Project
Development Manual.
</p></td></tr><tr class="question" title="11.2."><td align="left" valign="top"><a id="id1519579"></a><a id="id1519580"></a><p><b>11.2.</b></p></td><td align="left" valign="top"><p>
I only have Python 2.4 or 2.5 but BitBake requires Python 2.6 or 2.7.
Can I still use the Yocto Project?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
You can use a stand-alone tarball to provide Python 2.6.
You can find pre-built 32 and 64-bit versions of Python 2.6 at the following locations:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><a class="ulink" href="http://downloads.yoctoproject.org/releases/miscsupport/python-nativesdk-standalone-i686.tar.bz2" target="_top">32-bit tarball</a></p></li><li class="listitem"><p><a class="ulink" href="http://downloads.yoctoproject.org/releases/miscsupport/python-nativesdk-standalone-x86_64.tar.bz2" target="_top">64-bit tarball</a></p></li></ul></div><p>
</p><p>
These tarballs are self-contained with all required libraries and should work
on most Linux systems.
To use the tarballs extract them into the root
directory and run the appropriate command:
</p><pre class="literallayout">
$ export PATH=/opt/poky/sysroots/i586-pokysdk-linux/usr/bin/:$PATH
$ export PATH=/opt/poky/sysroots/x86_64-pokysdk-linux/usr/bin/:$PATH
</pre><p>
</p><p>
Once you run the command, BitBake uses Python 2.6.
</p></td></tr><tr class="question" title="11.3."><td align="left" valign="top"><a id="id1519623"></a><a id="id1519624"></a><p><b>11.3.</b></p></td><td align="left" valign="top"><p>
How can you claim Poky is stable?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
There are three areas that help with stability;
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>The Yocto Project team keeps
<a class="link" href="#poky" target="_top">Poky</a> small and focused.
It contains around 650 packages as compared to over 5000 for full
OpenEmbedded.</p></li><li class="listitem"><p>The Yocto Project only supports hardware that the
team has access to for testing.</p></li><li class="listitem"><p>The Yocto Project uses an an autobuilder,
which provides continuous build and integration tests.</p></li></ul></div><p>
</p></td></tr><tr class="question" title="11.4."><td align="left" valign="top"><a id="id1519656"></a><a id="id1519657"></a><p><b>11.4.</b></p></td><td align="left" valign="top"><p>
How do I get support for my board added to the Yocto Project?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
There are two main ways to get a board supported in the Yocto Project;
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Send the Yocto Project team information on the board
and if the team does not have it yet they will consider adding it.</p></li><li class="listitem"><p>Send the Yocto Project team the BitBake recipes if you have them.
</p></li></ul></div><p>
Usually, if the board is not completely exotic, adding support in
the Yocto Project is fairly straightforward.
</p></td></tr><tr class="question" title="11.5."><td align="left" valign="top"><a id="id1519678"></a><a id="id1519679"></a><p><b>11.5.</b></p></td><td align="left" valign="top"><p>
Are there any products using the OpenEmbedded build system (poky)?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
The <a class="ulink" href="http://vernier.com/labquest/" target="_top">Vernier LabQuest</a> is using
the OpenEmbedded build system.
See the <a class="ulink" href="http://www.vernier.com/products/interfaces/labq/" target="_top">Vernier LabQuest</a>
for more information.
There are a number of pre-production devices using the OpenEmbedded build system
and the Yocto Project team
announces them as soon as they are released.
</p></td></tr><tr class="question" title="11.6."><td align="left" valign="top"><a id="id1519700"></a><a id="id1519702"></a><p><b>11.6.</b></p></td><td align="left" valign="top"><p>
What does the OpenEmbedded build system produce as output?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
Because the same set of recipes can be used to create output of various formats, the
output of an OpenEmbedded build depends on how it was started.
Usually, the output is a flashable image ready for the target device.
</p></td></tr><tr class="question" title="11.7."><td align="left" valign="top"><a id="id1519711"></a><a id="id1519712"></a><p><b>11.7.</b></p></td><td align="left" valign="top"><p>
How do I add my package to the Yocto Project?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
To add a package, you need to create a BitBake recipe.
For information on how to add a package, see the section
"<a class="link" href="#usingpoky-extend-addpkg" target="_top">Adding a Package</a>"
in the Yocto Project Development Manual.
</p></td></tr><tr class="question" title="11.8."><td align="left" valign="top"><a id="id1519726"></a><a id="id1519727"></a><p><b>11.8.</b></p></td><td align="left" valign="top"><p>
Do I have to reflash my entire board with a new Yocto Project image when recompiling
a package?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
The OpenEmbedded build system can build packages in various formats such as
<code class="filename">ipk</code> for <code class="filename">ipkg</code>/<code class="filename">opkg</code>,
Debian package (<code class="filename">.deb</code>), or RPM.
The packages can then be upgraded using the package tools on the device, much like
on a desktop distribution such as Ubuntu or Fedora.
</p></td></tr><tr class="question" title="11.9."><td align="left" valign="top"><a id="id1519761"></a><a id="id1519762"></a><p><b>11.9.</b></p></td><td align="left" valign="top"><p>
What is GNOME Mobile and what is the difference between GNOME Mobile and GNOME?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
GNOME Mobile is a subset of the <a class="ulink" href="http://www.gnome.org" target="_top">GNOME</a>
platform targeted at mobile and embedded devices.
The the main difference between GNOME Mobile and standard GNOME is that
desktop-orientated libraries have been removed, along with deprecated libraries,
creating a much smaller footprint.
</p></td></tr><tr class="question" title="11.10."><td align="left" valign="top"><a id="id1519778"></a><a id="id1519780"></a><p><b>11.10.</b></p></td><td align="left" valign="top"><p>
I see the error '<code class="filename">chmod: XXXXX new permissions are r-xrwxrwx, not r-xr-xr-x</code>'.
What is wrong?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
You are probably running the build on an NTFS filesystem.
Use <code class="filename">ext2</code>, <code class="filename">ext3</code>, or <code class="filename">ext4</code> instead.
</p></td></tr><tr class="question" title="11.11."><td align="left" valign="top"><a id="id1519811"></a><a id="id1519812"></a><p><b>11.11.</b></p></td><td align="left" valign="top"><p>
How do I make the Yocto Project work in RHEL/CentOS?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
To get the Yocto Project working under RHEL/CentOS 5.1 you need to first
install some required packages.
The standard CentOS packages needed are:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>"Development tools" (selected during installation)</p></li><li class="listitem"><p><code class="filename">texi2html</code></p></li><li class="listitem"><p><code class="filename">compat-gcc-34</code></p></li></ul></div><p>
On top of these, you need the following external packages:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename">python-sqlite2</code> from
<a class="ulink" href="http://dag.wieers.com/rpm/packages/python-sqlite2/" target="_top">DAG repository</a>
</p></li><li class="listitem"><p><code class="filename">help2man</code> from
<a class="ulink" href="http://centos.karan.org/el4/extras/stable/x86_64/RPMS/repodata/repoview/help2man-0-1.33.1-2.html" target="_top">Karan repository</a></p></li></ul></div><p>
</p><p>
Once these packages are installed, the OpenEmbedded build system will be able
to build standard images.
However, there might be a problem with the QEMU emulator segfaulting.
You can either disable the generation of binary locales by setting
<code class="filename"><a class="link" href="#var-ENABLE_BINARY_LOCALE_GENERATION" title="ENABLE_BINARY_LOCALE_GENERATION">ENABLE_BINARY_LOCALE_GENERATION</a>
</code> to "0" or by removing the <code class="filename">linux-2.6-execshield.patch</code>
from the kernel and rebuilding it since that is the patch that causes the problems with QEMU.
</p></td></tr><tr class="question" title="11.12."><td align="left" valign="top"><a id="id1519899"></a><a id="id1519900"></a><p><b>11.12.</b></p></td><td align="left" valign="top"><p>
I see lots of 404 responses for files on
<code class="filename">http://www.yoctoproject.org/sources/*</code>. Is something wrong?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
Nothing is wrong.
The OpenEmbedded build system checks any configured source mirrors before downloading
from the upstream sources.
The build system does this searching for both source archives and
pre-checked out versions of SCM managed software.
These checks help in large installations because it can reduce load on the SCM servers
themselves.
The address above is one of the default mirrors configured into the
build system.
Consequently, if an upstream source disappears, the team
can place sources there so builds continue to work.
</p></td></tr><tr class="question" title="11.13."><td align="left" valign="top"><a id="id1519919"></a><a id="id1519920"></a><p><b>11.13.</b></p></td><td align="left" valign="top"><p>
I have machine-specific data in a package for one machine only but the package is
being marked as machine-specific in all cases, how do I prevent this?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
Set <code class="filename"><a class="link" href="#var-SRC_URI_OVERRIDES_PACKAGE_ARCH" title="SRC_URI_OVERRIDES_PACKAGE_ARCH">SRC_URI_OVERRIDES_PACKAGE_ARCH</a>
</code> = "0" in the <code class="filename">.bb</code> file but make sure the package is
manually marked as
machine-specific in the case that needs it.
The code that handles <code class="filename">SRC_URI_OVERRIDES_PACKAGE_ARCH</code> is in <code class="filename">base.bbclass</code>.
</p></td></tr><tr class="question" title="11.14."><td align="left" valign="top"><a id="id1519958"></a><a id="id1519959"></a><p><b>11.14.</b></p></td><td align="left" valign="top"><p>
I'm behind a firewall and need to use a proxy server. How do I do that?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
Most source fetching by the OpenEmbedded build system is done by <code class="filename">wget</code>
and you therefore need to specify the proxy settings in a
<code class="filename">.wgetrc</code> file in your home directory.
Example settings in that file would be
</p><pre class="literallayout">
http_proxy = http://proxy.yoyodyne.com:18023/
ftp_proxy = http://proxy.yoyodyne.com:18023/
</pre><p>
The Yocto Project also includes a <code class="filename">site.conf.sample</code>
file that shows how to configure CVS and Git proxy servers
if needed.
</p></td></tr><tr class="question" title="11.15."><td align="left" valign="top"><a id="id1519996"></a><a id="id1519997"></a><p><b>11.15.</b></p></td><td align="left" valign="top"><p>
I'm using Ubuntu Intrepid and am seeing build failures. What’s wrong?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
In Intrepid, Ubuntu turns on by default the normally optional compile-time security features
and warnings.
There are more details at
<a class="ulink" href="https://wiki.ubuntu.com/CompilerFlags" target="_top">https://wiki.ubuntu.com/CompilerFlags</a>.
You can work around this problem by disabling those options by adding
the following to the <code class="filename">BUILD_CPPFLAGS</code> variable in the
<code class="filename">conf/bitbake.conf</code> file.
</p><pre class="literallayout">
" -Wno-format-security -U_FORTIFY_SOURCE"
</pre><p>
</p></td></tr><tr class="question" title="11.16."><td align="left" valign="top"><a id="id1520034"></a><a id="id1520035"></a><p><b>11.16.</b></p></td><td align="left" valign="top"><p>
What’s the difference between <code class="filename">foo</code> and <code class="filename">foo-native</code>?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
The <code class="filename">*-native</code> targets are designed to run on the system
being used for the build.
These are usually tools that are needed to assist the build in some way such as
<code class="filename">quilt-native</code>, which is used to apply patches.
The non-native version is the one that runs on the target device.
</p></td></tr><tr class="question" title="11.17."><td align="left" valign="top"><a id="id1520068"></a><a id="id1520070"></a><p><b>11.17.</b></p></td><td align="left" valign="top"><p>
I'm seeing random build failures. Help?!
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
If the same build is failing in totally different and random ways,
the most likely explanation is that either the hardware you're running the
build on has some problem, or, if you are running the build under virtualisation,
the virtualisation probably has bugs.
The OpenEmbedded build system processes a massive amount of data causing lots of network, disk and
CPU activity and is sensitive to even single bit failures in any of these areas.
True random failures have always been traced back to hardware or virtualisation issues.
</p></td></tr><tr class="question" title="11.18."><td align="left" valign="top"><a id="id1520082"></a><a id="id1520083"></a><p><b>11.18.</b></p></td><td align="left" valign="top"><p>
What do we need to ship for license compliance?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
This is a difficult question and you need to consult your lawyer for the answer
for your specific case.
It is worth bearing in mind that for GPL compliance there needs to be enough
information shipped to allow someone else to rebuild the same end result
you are shipping.
This means sharing the source code, any patches applied to it, and also any
configuration information about how that package was configured and built.
</p></td></tr><tr class="question" title="11.19."><td align="left" valign="top"><a id="id1520094"></a><a id="id1520095"></a><p><b>11.19.</b></p></td><td align="left" valign="top"><p>
How do I disable the cursor on my touchscreen device?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
You need to create a form factor file as described in the
"<a class="link" href="#bsp-filelayout-misc-recipes" target="_top">Miscellaneous Recipe Files</a>"
section and set the <code class="filename">HAVE_TOUCHSCREEN</code> variable equal to one as follows:
</p><pre class="literallayout">
HAVE_TOUCHSCREEN=1
</pre><p>
</p></td></tr><tr class="question" title="11.20."><td align="left" valign="top"><a id="id1520125"></a><a id="id1520126"></a><p><b>11.20.</b></p></td><td align="left" valign="top"><p>
How do I make sure connected network interfaces are brought up by default?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
The default interfaces file provided by the netbase recipe does not
automatically bring up network interfaces.
Therefore, you will need to add a BSP-specific netbase that includes an interfaces
file.
See the "<a class="link" href="#bsp-filelayout-misc-recipes" target="_top">Miscellaneous Recipe Files</a>"
section for information on creating these types of miscellaneous recipe files.
</p><p>
For example, add the following files to your layer:
</p><pre class="literallayout">
meta-MACHINE/recipes-bsp/netbase/netbase/MACHINE/interfaces
meta-MACHINE/recipes-bsp/netbase/netbase_4.44.bbappend
</pre><p>
</p></td></tr><tr class="question" title="11.21."><td align="left" valign="top"><a id="id1520156"></a><a id="id1520157"></a><p><b>11.21.</b></p></td><td align="left" valign="top"><p>
How do I create images with more free space?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
Images are created to be 1.2 times the size of the populated root filesystem.
To modify this ratio so that there is more free space available, you need to
set the configuration value <code class="filename">IMAGE_OVERHEAD_FACTOR</code>.
For example, setting <code class="filename">IMAGE_OVERHEAD_FACTOR</code> to 1.5 sets
the image size ratio to one and a half times the size of the populated
root filesystem.
</p><pre class="literallayout">
IMAGE_OVERHEAD_FACTOR = "1.5"
</pre><p>
</p></td></tr><tr class="question" title="11.22."><td align="left" valign="top"><a id="id1520188"></a><a id="id1520190"></a><p><b>11.22.</b></p></td><td align="left" valign="top"><p>
Why don't you support directories with spaces in the pathnames?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
The Yocto Project team has tried to do this before but too many of the tools
the OpenEmbedded build system depends on such as <code class="filename">autoconf</code>
break when they find spaces in pathnames.
Until that situation changes, the team will not support spaces in pathnames.
</p></td></tr><tr class="question" title="11.23."><td align="left" valign="top"><a id="id1520206"></a><a id="id1520207"></a><p><b>11.23.</b></p></td><td align="left" valign="top"><p>
How do I use an external toolchain?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
The toolchain configuration is very flexible and customizable.
It is primarily controlled with the
<code class="filename"><a class="link" href="#var-TCMODE" title="TCMODE">TCMODE</a></code> variable.
This variable controls which <code class="filename">tcmode-*.inc</code> file to include
from the <code class="filename">meta/conf/distro/include</code> directory within the
<a class="link" href="#source-directory" target="_top">source directory</a>.
</p><p>
The default value of <code class="filename">TCMODE</code> is "default"
(i.e. <code class="filename">tcmode-default.inc</code>).
However, other patterns are accepted.
In particular, "external-*" refers to external toolchains of which there are some
basic examples included in the OpenEmbedded Core (<code class="filename">meta</code>).
You can use your own custom toolchain definition in your own layer
(or as defined in the <code class="filename">local.conf</code> file) at the location
<code class="filename">conf/distro/include/tcmode-*.inc</code>.
</p><p>
In addition to the toolchain configuration, you also need a corresponding toolchain recipe file.
This recipe file needs to package up any pre-built objects in the toolchain such as
<code class="filename">libgcc</code>, <code class="filename">libstdcc++</code>,
any locales, and <code class="filename">libc</code>.
An example is the <code class="filename">external-sourcery-toolchain.bb</code>, which is located
in <code class="filename">meta/recipes-core/meta/</code> within the source directory.
</p></td></tr><tr class="question" title="11.24."><td align="left" valign="top"><a id="id1520281"></a><a id="id1520316"></a><p><b>11.24.</b></p></td><td align="left" valign="top"><p><a id="how-does-the-yocto-project-obtain-source-code-and-will-it-work-behind-my-firewall-or-proxy-server"></a>
How does the OpenEmbedded build system obtain source code and will it work behind my
firewall or proxy server?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
The way the build system obtains source code is highly configurable.
You can setup the build system to get source code in most environments if
HTTP transport is available.
</p><p>
When the build system searches for source code, it first tries the local download directory.
If that location fails, Poky tries PREMIRRORS, the upstream source,
and then MIRRORS in that order.
</p><p>
By default, the OpenEmbedded build system uses the Yocto Project source PREMIRRORS
for SCM-based sources,
upstreams for normal tarballs, and then falls back to a number of other mirrors
including the Yocto Project source mirror if those fail.
</p><p>
As an example, you could add a specific server for Poky to attempt before any
others by adding something like the following to the <code class="filename">local.conf</code>
configuration file:
</p><pre class="literallayout">
PREMIRRORS_prepend = "\
git://.*/.* http://www.yoctoproject.org/sources/ \n \
ftp://.*/.* http://www.yoctoproject.org/sources/ \n \
http://.*/.* http://www.yoctoproject.org/sources/ \n \
https://.*/.* http://www.yoctoproject.org/sources/ \n"
</pre><p>
</p><p>
These changes cause Poky to intercept Git, FTP, HTTP, and HTTPS
requests and direct them to the <code class="filename">http://</code> sources mirror.
You can use <code class="filename">file://</code> URLs to point to local directories
or network shares as well.
</p><p>
Aside from the previous technique, these options also exist:
</p><pre class="literallayout">
BB_NO_NETWORK = "1"
</pre><p>
This statement tells BitBake to throw an error instead of trying to access the
Internet.
This technique is useful if you want to ensure code builds only from local sources.
</p><p>
Here is another technique:
</p><pre class="literallayout">
BB_FETCH_PREMIRRORONLY = "1"
</pre><p>
This statement limits Poky to pulling source from the PREMIRRORS only.
Again, this technique is useful for reproducing builds.
</p><p>
Here is another technique:
</p><pre class="literallayout">
BB_GENERATE_MIRROR_TARBALLS = "1"
</pre><p>
This statement tells Poky to generate mirror tarballs.
This technique is useful if you want to create a mirror server.
If not, however, the technique can simply waste time during the build.
</p><p>
Finally, consider an example where you are behind an HTTP-only firewall.
You could make the following changes to the <code class="filename">local.conf</code>
configuration file as long as the PREMIRROR server is up to date:
</p><pre class="literallayout">
PREMIRRORS_prepend = "\
ftp://.*/.* http://www.yoctoproject.org/sources/ \n \
http://.*/.* http://www.yoctoproject.org/sources/ \n \
https://.*/.* http://www.yoctoproject.org/sources/ \n"
BB_FETCH_PREMIRRORONLY = "1"
</pre><p>
These changes would cause Poky to successfully fetch source over HTTP and
any network accesses to anything other than the PREMIRROR would fail.
</p><p>
The build system also honors the standard shell environment variables
<code class="filename">http_proxy</code>, <code class="filename">ftp_proxy</code>,
<code class="filename">https_proxy</code>, and <code class="filename">all_proxy</code>
to redirect requests through proxy servers.
</p></td></tr><tr class="question" title="11.25."><td align="left" valign="top"><a id="id1520463"></a><a id="id1520464"></a><p><b>11.25.</b></p></td><td align="left" valign="top"><p>
Can I get rid of build output so I can start over?
</p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p>
Yes - you can easily do this.
When you use BitBake to build an image, all the build output goes into the
directory created when you source the <code class="filename">oe-init-build-env</code>
setup file.
By default, this <a class="link" href="#build-directory" target="_top">build directory</a>
is named <code class="filename">build</code> but can be named
anything you want.
</p><p>
Within the build directory is the <code class="filename">tmp</code> directory.
To remove all the build output yet preserve any source code or downloaded files
from previous builds, simply remove the <code class="filename">tmp</code> directory.
</p></td></tr></tbody></table></div></div>
<div class="chapter" title="Chapter 12. Contributing to the Yocto Project"><div class="titlepage"><div><div><h2 class="title"><a id="resources"></a>Chapter 12. Contributing to the Yocto Project</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="#resources-intro">12.1. Introduction</a></span></dt><dt><span class="section"><a href="#resources-bugtracker">12.2. Tracking Bugs</a></span></dt><dt><span class="section"><a href="#resources-mailinglist">12.3. Mailing lists</a></span></dt><dt><span class="section"><a href="#resources-irc">12.4. Internet Relay Chat (IRC)</a></span></dt><dt><span class="section"><a href="#resources-links">12.5. Links</a></span></dt><dt><span class="section"><a href="#resources-contributions">12.6. Contributions</a></span></dt></dl></div><div class="section" title="12.1. Introduction"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="resources-intro"></a>12.1. Introduction</h2></div></div></div><p>
The Yocto Project team is happy for people to experiment with the Yocto Project.
A number of places exist to find help if you run into difficulties or find bugs.
To find out how to download source code,
see the "<a class="link" href="#local-yp-release" target="_top">Yocto Project Release</a>"
list item in the Yocto Project Development Manual.
</p></div><div class="section" title="12.2. Tracking Bugs"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="resources-bugtracker"></a>12.2. Tracking Bugs</h2></div></div></div><p>
If you find problems with the Yocto Project, you should report them using the
Bugzilla application at <a class="ulink" href="http://bugzilla.yoctoproject.org" target="_top">http://bugzilla.yoctoproject.org</a>.
</p></div><div class="section" title="12.3. Mailing lists"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="resources-mailinglist"></a>12.3. Mailing lists</h2></div></div></div><p>
There are a number of mailing lists maintained by the Yocto Project as well as
related OpenEmbedded mailing lists for discussion, patch submission and announcements.
To subscribe to one of the following mailing lists, click on the appropriate URL
in the following list and follow the instructions:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><a class="ulink" href="http://lists.yoctoproject.org/listinfo/yocto" target="_top">http://lists.yoctoproject.org/listinfo/yocto</a> -
General Yocto Project discussion mailing list. </p></li><li class="listitem"><p><a class="ulink" href="http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/openembedded-core" target="_top">http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/openembedded-core</a> -
Discussion mailing list about OpenEmbedded-Core (the core metadata).</p></li><li class="listitem"><p><a class="ulink" href="http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/openembedded-devel" target="_top">http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/openembedded-devel</a> -
Discussion mailing list about OpenEmbedded.</p></li><li class="listitem"><p><a class="ulink" href="http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/bitbake-devel" target="_top">http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/bitbake-devel</a> -
Discussion mailing list about the BitBake build tool.</p></li><li class="listitem"><p><a class="ulink" href="http://lists.yoctoproject.org/listinfo/poky" target="_top">http://lists.yoctoproject.org/listinfo/poky</a> -
Discussion mailing list about Poky.</p></li><li class="listitem"><p><a class="ulink" href="http://lists.yoctoproject.org/listinfo/yocto-announce" target="_top">http://lists.yoctoproject.org/listinfo/yocto-announce</a> -
Mailing list to receive official Yocto Project release and milestone
announcements.</p></li></ul></div><p>
</p></div><div class="section" title="12.4. Internet Relay Chat (IRC)"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="resources-irc"></a>12.4. Internet Relay Chat (IRC)</h2></div></div></div><p>
Two IRC channels on freenode are available for the Yocto Project and Poky discussions:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><code class="filename">#yocto</code></p></li><li class="listitem"><p><code class="filename">#poky</code></p></li></ul></div><p>
</p></div><div class="section" title="12.5. Links"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="resources-links"></a>12.5. Links</h2></div></div></div><p>
Following is a list of resources you will find helpful:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em><a class="ulink" href="http://www.yoctoproject.org" target="_top">The Yocto Project website</a>:
</em></span> The home site for the Yocto Project.</p></li><li class="listitem"><p><span class="emphasis"><em><a class="ulink" href="http://www.intel.com/" target="_top">Intel Corporation</a>:</em></span>
The company who acquired OpenedHand in 2008 and began development on the
Yocto Project.</p></li><li class="listitem"><p><span class="emphasis"><em><a class="ulink" href="http://www.openembedded.org" target="_top">OpenEmbedded</a>:</em></span>
The upstream, generic, embedded distribution used as the basis for the build system in the
Yocto Project.
Poky derives from and contributes back to the OpenEmbedded project.</p></li><li class="listitem"><p><span class="emphasis"><em><a class="ulink" href="http://developer.berlios.de/projects/bitbake/" target="_top">
BitBake</a>:</em></span> The tool used to process metadata.</p></li><li class="listitem"><p><span class="emphasis"><em><a class="ulink" href="http://docs.openembedded.org/bitbake/html/" target="_top">
BitBake User Manual</a>:</em></span> A comprehensive guide to the BitBake tool.
</p></li><li class="listitem"><p><span class="emphasis"><em><a class="ulink" href="http://wiki.qemu.org/Index.html" target="_top">QEMU</a>:
</em></span> An open source machine emulator and virtualizer.</p></li></ul></div><p>
</p></div><div class="section" title="12.6. Contributions"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="resources-contributions"></a>12.6. Contributions</h2></div></div></div><p>
The Yocto Project gladly accepts contributions.
You can submit changes to the project either by creating and sending pull requests,
or by submitting patches through email.
For information on how to do both, see the
"<a class="link" href="#how-to-submit-a-change" target="_top">How to Submit a Change</a>"
section in the Yocto Project Development Manual.
</p></div></div>
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