kernel-dev: Created file structure for new kernel-dev manual.
(From yocto-docs rev: 25be3ebb7713b875c4ec6e3723961b7dd860295d) Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
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<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
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[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
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<chapter id='kernel-how-to'>
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<title>Working with the Yocto Project Kernel</title>
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<section id='actions-org'>
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<title>Introduction</title>
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<para>
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This chapter describes how to accomplish tasks involving a kernel's tree structure.
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The information is designed to help the developer that wants to modify the Yocto
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Project kernel and contribute changes upstream to the Yocto Project.
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The information covers the following:
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<itemizedlist>
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<listitem><para>Tree construction</para></listitem>
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<listitem><para>Build strategies</para></listitem>
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<listitem><para>Workflow examples</para></listitem>
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</itemizedlist>
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</para>
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</section>
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<section id='tree-construction'>
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<title>Tree Construction</title>
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<para>
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This section describes construction of the Yocto Project kernel source repositories
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as accomplished by the Yocto Project team to create kernel repositories.
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These kernel repositories are found under the heading "Yocto Linux Kernel" at
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<ulink url='&YOCTO_GIT_URL;/cgit.cgi'>&YOCTO_GIT_URL;/cgit.cgi</ulink>
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and can be shipped as part of a Yocto Project release.
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The team creates these repositories by
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compiling and executing the set of feature descriptions for every BSP/feature
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in the product.
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Those feature descriptions list all necessary patches,
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configuration, branching, tagging and feature divisions found in a kernel.
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Thus, the Yocto Project kernel repository (or tree) is built.
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</para>
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<para>
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The existence of this tree allows you to access and clone a particular
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Yocto Project kernel repository and use it to build images based on their configurations
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and features.
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</para>
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<para>
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You can find the files used to describe all the valid features and BSPs
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in the Yocto Project kernel in any clone of the Yocto Project kernel source repository
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Git tree.
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For example, the following command clones the Yocto Project baseline kernel that
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branched off of <filename>linux.org</filename> version 3.4:
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<literallayout class='monospaced'>
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$ git clone git://git.yoctoproject.org/linux-yocto-3.4
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</literallayout>
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For another example of how to set up a local Git repository of the Yocto Project
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kernel files, see the
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"<ulink url='&YOCTO_DOCS_DEV_URL;#local-kernel-files'>Yocto Project Kernel</ulink>" bulleted
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item in the Yocto Project Development Manual.
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</para>
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<para>
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Once you have cloned the kernel Git repository on your local machine, you can
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switch to the <filename>meta</filename> branch within the repository.
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Here is an example that assumes the local Git repository for the kernel is in
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a top-level directory named <filename>linux-yocto-3.4</filename>:
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<literallayout class='monospaced'>
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$ cd ~/linux-yocto-3.4
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$ git checkout -b meta origin/meta
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</literallayout>
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Once you have checked out and switched to the <filename>meta</filename> branch,
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you can see a snapshot of all the kernel configuration and feature descriptions that are
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used to build that particular kernel repository.
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These descriptions are in the form of <filename>.scc</filename> files.
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</para>
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<para>
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You should realize, however, that browsing your local kernel repository
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for feature descriptions and patches is not an effective way to determine what is in a
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particular kernel branch.
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Instead, you should use Git directly to discover the changes in a branch.
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Using Git is an efficient and flexible way to inspect changes to the kernel.
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For examples showing how to use Git to inspect kernel commits, see the following sections
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in this chapter.
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<note>
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Ground up reconstruction of the complete kernel tree is an action only taken by the
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Yocto Project team during an active development cycle.
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When you create a clone of the kernel Git repository, you are simply making it
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efficiently available for building and development.
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</note>
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</para>
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<para>
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The following steps describe what happens when the Yocto Project Team constructs
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the Yocto Project kernel source Git repository (or tree) found at
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<ulink url='&YOCTO_GIT_URL;/cgit.cgi'></ulink> given the
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introduction of a new top-level kernel feature or BSP.
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These are the actions that effectively create the tree
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that includes the new feature, patch or BSP:
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<orderedlist>
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<listitem><para>A top-level kernel feature is passed to the kernel build subsystem.
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Normally, this feature is a BSP for a particular kernel type.</para></listitem>
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<listitem><para>The file that describes the top-level feature is located by searching
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these system directories:
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<itemizedlist>
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<listitem><para>The in-tree kernel-cache directories, which are located
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in <filename>meta/cfg/kernel-cache</filename></para></listitem>
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<listitem><para>Areas pointed to by <filename>SRC_URI</filename> statements
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found in recipes</para></listitem>
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</itemizedlist>
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For a typical build, the target of the search is a
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feature description in an <filename>.scc</filename> file
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whose name follows this format:
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<literallayout class='monospaced'>
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<bsp_name>-<kernel_type>.scc
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</literallayout>
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</para></listitem>
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<listitem><para>Once located, the feature description is either compiled into a simple script
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of actions, or into an existing equivalent script that is already part of the
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shipped kernel.</para></listitem>
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<listitem><para>Extra features are appended to the top-level feature description.
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These features can come from the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_FEATURES'><filename>KERNEL_FEATURES</filename></ulink>
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variable in recipes.</para></listitem>
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<listitem><para>Each extra feature is located, compiled and appended to the script
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as described in step three.</para></listitem>
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<listitem><para>The script is executed to produce a series of <filename>meta-*</filename>
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directories.
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These directories are descriptions of all the branches, tags, patches and configurations that
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need to be applied to the base Git repository to completely create the
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source (build) branch for the new BSP or feature.</para></listitem>
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<listitem><para>The base repository is cloned, and the actions
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listed in the <filename>meta-*</filename> directories are applied to the
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tree.</para></listitem>
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<listitem><para>The Git repository is left with the desired branch checked out and any
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required branching, patching and tagging has been performed.</para></listitem>
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</orderedlist>
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</para>
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<para>
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The kernel tree is now ready for developer consumption to be locally cloned,
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configured, and built into a Yocto Project kernel specific to some target hardware.
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<note><para>The generated <filename>meta-*</filename> directories add to the kernel
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as shipped with the Yocto Project release.
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Any add-ons and configuration data are applied to the end of an existing branch.
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The full repository generation that is found in the
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official Yocto Project kernel repositories at
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<ulink url='&YOCTO_GIT_URL;/cgit.cgi'>http://git.yoctoproject.org/cgit.cgi</ulink>
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is the combination of all supported boards and configurations.</para>
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<para>The technique the Yocto Project team uses is flexible and allows for seamless
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blending of an immutable history with additional patches specific to a
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deployment.
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Any additions to the kernel become an integrated part of the branches.</para>
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</note>
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</para>
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</section>
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<section id='build-strategy'>
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<title>Build Strategy</title>
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<para>
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Once a local Git repository of the Yocto Project kernel exists on a development system,
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you can consider the compilation phase of kernel development - building a kernel image.
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|
Some prerequisites exist that are validated by the build process before compilation
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starts:
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</para>
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<itemizedlist>
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<listitem><para>The
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<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> points
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to the kernel Git repository.</para></listitem>
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<listitem><para>A BSP build branch exists.
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|
This branch has the following form:
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<literallayout class='monospaced'>
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<kernel_type>/<bsp_name>
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</literallayout></para></listitem>
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</itemizedlist>
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<para>
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|
The OpenEmbedded build system makes sure these conditions exist before attempting compilation.
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|
Other means, however, do exist, such as as bootstrapping a BSP, see
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the "<link linkend='workflow-examples'>Workflow Examples</link>".
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|
</para>
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<para>
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|
Before building a kernel, the build process verifies the tree
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and configures the kernel by processing all of the
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configuration "fragments" specified by feature descriptions in the <filename>.scc</filename>
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files.
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As the features are compiled, associated kernel configuration fragments are noted
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and recorded in the <filename>meta-*</filename> series of directories in their compilation order.
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The fragments are migrated, pre-processed and passed to the Linux Kernel
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Configuration subsystem (<filename>lkc</filename>) as raw input in the form
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of a <filename>.config</filename> file.
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The <filename>lkc</filename> uses its own internal dependency constraints to do the final
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processing of that information and generates the final <filename>.config</filename> file
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that is used during compilation.
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</para>
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<para>
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Using the board's architecture and other relevant values from the board's template,
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kernel compilation is started and a kernel image is produced.
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</para>
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<para>
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The other thing that you notice once you configure a kernel is that
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the build process generates a build tree that is separate from your kernel's local Git
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source repository tree.
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This build tree has a name that uses the following form, where
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<filename>${MACHINE}</filename> is the metadata name of the machine (BSP) and "kernel_type" is one
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of the Yocto Project supported kernel types (e.g. "standard"):
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<literallayout class='monospaced'>
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linux-${MACHINE}-<kernel_type>-build
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</literallayout>
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</para>
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<para>
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The existing support in the <filename>kernel.org</filename> tree achieves this
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default functionality.
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</para>
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<para>
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This behavior means that all the generated files for a particular machine or BSP are now in
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the build tree directory.
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The files include the final <filename>.config</filename> file, all the <filename>.o</filename>
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files, the <filename>.a</filename> files, and so forth.
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|
Since each machine or BSP has its own separate build directory in its own separate branch
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of the Git repository, you can easily switch between different builds.
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</para>
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</section>
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<section id='workflow-examples'>
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<title>Workflow Examples</title>
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|
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|
<para>
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|
As previously noted, the Yocto Project kernel has built-in Git integration.
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|
However, these utilities are not the only way to work with the kernel repository.
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|
The Yocto Project has not made changes to Git or to other tools that
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would invalidate alternate workflows.
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|
Additionally, the way the kernel repository is constructed results in using
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only core Git functionality, thus allowing any number of tools or front ends to use the
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resulting tree.
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|
</para>
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|
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<para>
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This section contains several workflow examples.
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Many of the examples use Git commands.
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|
You can find Git documentation at
|
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|
<ulink url='http://git-scm.com/documentation'></ulink>.
|
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|
You can find a simple overview of using Git with the Yocto Project in the
|
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|
"<ulink url='&YOCTO_DOCS_DEV_URL;#git'>Git</ulink>"
|
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|
section of the Yocto Project Development Manual.
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|
</para>
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|
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<section id='change-inspection-kernel-changes-commits'>
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<title>Change Inspection: Changes/Commits</title>
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|
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<para>
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A common question when working with a kernel is:
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"What changes have been applied to this tree?"
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</para>
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|
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<para>
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|
In projects that have a collection of directories that
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contain patches to the kernel, it is possible to inspect or "grep" the contents
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of the directories to get a general feel for the changes.
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|
This sort of patch inspection is not an efficient way to determine what has been
|
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done to the kernel.
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The reason it is inefficient is because there are many optional patches that are
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selected based on the kernel type and the feature description.
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Additionally, patches could exist in directories that are not included in the search.
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</para>
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|
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<para>
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|
A more efficient way to determine what has changed in the branch is to use
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Git and inspect or search the kernel tree.
|
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|
This method gives you a full view of not only the source code modifications,
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|
but also provides the reasons for the changes.
|
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|
</para>
|
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|
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<section id='what-changed-in-a-kernel'>
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<title>What Changed in a Kernel?</title>
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|
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|
<para>
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|
Following are a few examples that show how to use Git commands to examine changes.
|
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|
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.
|
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|
<note>
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|
In the following examples, unless you provide a commit range,
|
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|
<filename>kernel.org</filename> history is blended with Yocto Project
|
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|
kernel changes.
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|
You can form ranges by using branch names from the kernel tree as the
|
||||||
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upper and lower commit markers with the Git commands.
|
||||||
|
You can see the branch names through the web interface to the
|
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|
Yocto Project source repositories at
|
||||||
|
<ulink url='http://git.yoctoproject.org/cgit.cgi'></ulink>.
|
||||||
|
For example, the branch names for the <filename>linux-yocto-3.4</filename>
|
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|
kernel repository can be seen at
|
||||||
|
<ulink url='http://git.yoctoproject.org/cgit.cgi/linux-yocto-3.4/refs/heads'></ulink>.
|
||||||
|
</note>
|
||||||
|
To see a full range of the changes, use the
|
||||||
|
<filename>git whatchanged</filename> command and specify a commit range
|
||||||
|
for the branch (<filename><commit>..<commit></filename>).
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Here is an example that looks at what has changed in the
|
||||||
|
<filename>emenlow</filename> branch of the
|
||||||
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<filename>linux-yocto-3.4</filename> kernel.
|
||||||
|
The lower commit range is the commit associated with the
|
||||||
|
<filename>standard/base</filename> branch, while
|
||||||
|
the upper commit range is the commit associated with the
|
||||||
|
<filename>standard/emenlow</filename> branch.
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git whatchanged origin/standard/base..origin/standard/emenlow
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
To see a summary of changes use the <filename>git log</filename> command.
|
||||||
|
Here is an example using the same branches:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git log --oneline origin/standard/base..origin/standard/emenlow
|
||||||
|
</literallayout>
|
||||||
|
The <filename>git log</filename> output might be more useful than
|
||||||
|
the <filename>git whatchanged</filename> as you get
|
||||||
|
a short, one-line summary of each change and not the entire commit.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
If you want to see code differences associated with all the changes, use
|
||||||
|
the <filename>git diff</filename> command.
|
||||||
|
Here is an example:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git diff origin/standard/base..origin/standard/emenlow
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
You can see the commit log messages and the text differences using the
|
||||||
|
<filename>git show</filename> command:
|
||||||
|
Here is an example:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git show origin/standard/base..origin/standard/emenlow
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
You can create individual patches for each change by using the
|
||||||
|
<filename>git format-patch</filename> command.
|
||||||
|
Here is an example that that creates patch files for each commit and
|
||||||
|
places them in your <filename>Documents</filename> directory:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git format-patch -o $HOME/Documents origin/standard/base..origin/standard/emenlow
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='show-a-particular-feature-or-branch-change'>
|
||||||
|
<title>Show a Particular Feature or Branch Change</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note>
|
||||||
|
Because BSP branch, <filename>kernel.org</filename>, and feature tags are all
|
||||||
|
present, there could be many tags.
|
||||||
|
</note>
|
||||||
|
The <filename>git show <tag></filename> command shows changes that are tagged by
|
||||||
|
a feature.
|
||||||
|
Here is an example that shows changes tagged by the <filename>systemtap</filename>
|
||||||
|
feature:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git show systemtap
|
||||||
|
</literallayout>
|
||||||
|
You can use the <filename>git branch --contains <tag></filename> command
|
||||||
|
to show the branches that contain a particular feature.
|
||||||
|
This command shows the branches that contain the <filename>systemtap</filename>
|
||||||
|
feature:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git branch --contains systemtap
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
You can use many other comparisons to isolate BSP and kernel changes.
|
||||||
|
For example, you can compare against <filename>kernel.org</filename> tags
|
||||||
|
such as the <filename>v3.4</filename> tag.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='development-saving-kernel-modifications'>
|
||||||
|
<title>Development: Saving Kernel Modifications</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
This section and its sub-sections, describe general application of Git's
|
||||||
|
<filename>push</filename> and <filename>pull</filename> 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
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#pushing-a-change-upstream'>Using Scripts to Push a Change
|
||||||
|
Upstream and Request a Pull</ulink>" and
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#submitting-a-patch'>Using Email to Submit a Patch</ulink>"
|
||||||
|
sections in the Yocto Project Development Manual.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
There are many ways to save kernel modifications.
|
||||||
|
The technique employed
|
||||||
|
depends on the destination for the patches:
|
||||||
|
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>Bulk storage</para></listitem>
|
||||||
|
<listitem><para>Internal sharing either through patches or by using Git</para></listitem>
|
||||||
|
<listitem><para>External submissions</para></listitem>
|
||||||
|
<listitem><para>Exporting for integration into another Source Code
|
||||||
|
Manager (SCM)</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Because of the following list of issues, the destination of the patches also influences
|
||||||
|
the method for gathering them:
|
||||||
|
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>Bisectability</para></listitem>
|
||||||
|
<listitem><para>Commit headers</para></listitem>
|
||||||
|
<listitem><para>Division of subsystems for separate submission or review</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<section id='bulk-export'>
|
||||||
|
<title>Bulk Export</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note>
|
||||||
|
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.
|
||||||
|
</note>
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# bulk export of ALL modifications without separation or division
|
||||||
|
# of the changes
|
||||||
|
|
||||||
|
$ git add .
|
||||||
|
$ git commit -s -a -m <msg>
|
||||||
|
or
|
||||||
|
$ git commit -s -a # and interact with $EDITOR
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Once the changes are exported, you can restore them manually using a template
|
||||||
|
or through integration with the <filename>default_kernel</filename>.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='incremental-planned-sharing'>
|
||||||
|
<title>Incremental/Planned Sharing</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
During development, the following commands are of interest.
|
||||||
|
For full Git documentation, refer to the Git documentation at
|
||||||
|
<ulink url='http://github.com'></ulink>.
|
||||||
|
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# edit a file
|
||||||
|
$ vi <path>/file
|
||||||
|
# stage the change
|
||||||
|
$ git add <path>/file
|
||||||
|
# commit the change
|
||||||
|
$ git commit -s
|
||||||
|
# remove a file
|
||||||
|
$ git rm <path>/file
|
||||||
|
# commit the change
|
||||||
|
$ git commit -s
|
||||||
|
|
||||||
|
... etc.
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 <filename>push</filename> and
|
||||||
|
<filename>pull</filename> operations for
|
||||||
|
distributed development, you should consider the ramifications of changing a
|
||||||
|
commit that you have already shared with others.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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:
|
||||||
|
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ Git add <path>/file
|
||||||
|
$ Git commit --amend
|
||||||
|
$ Git rebase or Git rebase -i
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Again, assuming that the changes have not been pushed upstream, and that
|
||||||
|
no pending works-in-progress exist (use <filename>git status</filename> to check), then
|
||||||
|
you can revert (undo) commits by using the following commands:
|
||||||
|
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# 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^
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 <filename>push</filename> or <filename>pull</filename> 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 <filename>kernel.org</filename> best
|
||||||
|
practices, which is recommended.
|
||||||
|
<note>
|
||||||
|
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.
|
||||||
|
</note>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<section id='export-internally-via-patches'>
|
||||||
|
<title>Exporting Changes Internally by Using Patches</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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
|
||||||
|
<filename>git am</filename> command to reproduce the original commit and all
|
||||||
|
the related information such as author, date, commit log, and so forth.
|
||||||
|
<note>
|
||||||
|
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.
|
||||||
|
</note>
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# <first-commit> 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 <dir> <first commit>..<last commit>
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
In other words:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# Identify commits of interest.
|
||||||
|
|
||||||
|
# If the tree was tagged before development
|
||||||
|
$ git format-patch -o <save dir> <tag>
|
||||||
|
|
||||||
|
# If no tags are available
|
||||||
|
$ git format-patch -o <save dir> HEAD^ # last commit
|
||||||
|
$ git format-patch -o <save dir> HEAD^^ # last 2 commits
|
||||||
|
$ git whatchanged # identify last commit
|
||||||
|
$ git format-patch -o <save dir> <commit id>
|
||||||
|
$ git format-patch -o <save dir> <rev-list>
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='export-internally-via-git'>
|
||||||
|
<title>Exporting Changes Internally by Using Git</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Use this command form to push the changes:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git push ssh://<master_server>/<path_to_repo>
|
||||||
|
<local_branch>:<remote_branch>
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
For example, the following command pushes the changes from your local branch
|
||||||
|
<filename>yocto/standard/common-pc/base</filename> to the remote branch with the same name
|
||||||
|
in the master repository <filename>//git.mycompany.com/pub/git/kernel-3.4</filename>.
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git push ssh://git.mycompany.com/pub/git/kernel-3.4 \
|
||||||
|
yocto/standard/common-pc/base:yocto/standard/common-pc/base
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
A pull request entails using the <filename>git request-pull</filename> command to compose
|
||||||
|
an email to the
|
||||||
|
maintainer requesting that a branch be pulled into the master repository, see
|
||||||
|
<ulink url='http://github.com/guides/pull-requests'></ulink> for an example.
|
||||||
|
<note>
|
||||||
|
Other commands such as <filename>git stash</filename> or branching can also be used to save
|
||||||
|
changes, but are not covered in this document.
|
||||||
|
</note>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='export-for-external-upstream-submission'>
|
||||||
|
<title>Exporting Changes for External (Upstream) Submission</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note>
|
||||||
|
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:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>
|
||||||
|
<ulink url='http://linux.yyz.us/patch-format.html'></ulink></para></listitem>
|
||||||
|
<listitem><para>Documentation/SubmittingPatches (in any linux
|
||||||
|
kernel source tree)</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</note>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#how-to-submit-a-change'>How to Submit a
|
||||||
|
Change</ulink>" section in the Yocto Project Development Manual.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
If the initial commits were not properly documented or do not meet those standards,
|
||||||
|
you can re-base by using the <filename>git rebase -i</filename> 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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 <filename>git send-email</filename> is commonly used to ensure
|
||||||
|
that patches are properly
|
||||||
|
formatted for easy application and avoid mailer-induced patch damage.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The following is an example of dumping patches for external submission:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# dump the last 4 commits
|
||||||
|
$ git format-patch --thread -n -o ~/rr/ HEAD^^^^
|
||||||
|
$ git send-email --compose --subject '[RFC 0/N] <patch series summary>' \
|
||||||
|
--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
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='export-for-import-into-other-scm'>
|
||||||
|
<title>Exporting Changes for Import into Another SCM</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='scm-working-with-the-yocto-project-kernel-in-another-scm'>
|
||||||
|
<title>Working with the Yocto Project Kernel in Another SCM</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>The delivered Yocto Project kernel must be exported into the second
|
||||||
|
SCM.</para></listitem>
|
||||||
|
<listitem><para>Development must be exported from that secondary SCM into a
|
||||||
|
format that can be used by the OpenEmbedded build system.</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<section id='exporting-delivered-kernel-to-scm'>
|
||||||
|
<title>Exporting the Delivered Kernel to the SCM</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The following commands illustrate some of the steps you could use to
|
||||||
|
import the <filename>yocto/standard/common-pc/base</filename>
|
||||||
|
kernel into a secondary SCM:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git checkout yocto/standard/common-pc/base
|
||||||
|
$ cd .. ; echo linux/.git > .cvsignore
|
||||||
|
$ cvs import -m "initial import" linux MY_COMPANY start
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
You could now relocate the CVS repository and use it in a centralized manner.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The following commands illustrate how you can condense and merge two BSPs into a
|
||||||
|
second SCM:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ 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 > .cvsignore
|
||||||
|
$ cvs import -m "initial import" linux MY_COMPANY start
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='importing-changes-for-build'>
|
||||||
|
<title>Importing Changes for the Build</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='bsp-creating'>
|
||||||
|
<title>Creating a BSP Based on an Existing Similar BSP</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 new BSP, see
|
||||||
|
the "<ulink url='&YOCTO_DOCS_BSP_URL;#creating-a-new-bsp-layer-using-the-yocto-bsp-script'>Creating a New BSP Layer Using the yocto-bsp Script</ulink>" section in the
|
||||||
|
Yocto Project Board Support Package (BSP) Developer's Guide, or see the
|
||||||
|
<ulink url='&YOCTO_WIKI_URL;/wiki/Transcript:_creating_one_generic_Atom_BSP_from_another'>Transcript:_creating_one_generic_Atom_BSP_from_another</ulink>
|
||||||
|
wiki page.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The basic steps you need to follow are:
|
||||||
|
<orderedlist>
|
||||||
|
<listitem><para><emphasis>Make sure you have set up a local Source Directory:</emphasis>
|
||||||
|
You must create a local
|
||||||
|
<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>
|
||||||
|
by either creating a Git repository (recommended) or
|
||||||
|
extracting a Yocto Project release tarball.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Choose an existing BSP available with the Yocto Project:</emphasis>
|
||||||
|
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
|
||||||
|
<ulink url='&YOCTO_HOME_URL;/download'></ulink>.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Be sure you have the Base BSP:</emphasis>
|
||||||
|
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.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Make a copy of the existing BSP, thus isolating your new
|
||||||
|
BSP work:</emphasis>
|
||||||
|
Copying the existing BSP file structure gives you a new area in which to work.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Make configuration and recipe changes to your new BSP:</emphasis>
|
||||||
|
Configuration changes involve the files in the BSP's <filename>conf</filename>
|
||||||
|
directory.
|
||||||
|
Changes include creating a machine-specific configuration file and editing the
|
||||||
|
<filename>layer.conf</filename> 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.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Prepare for the build:</emphasis>
|
||||||
|
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 <filename>local.conf</filename> and <filename>bblayers.conf</filename>
|
||||||
|
files.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Build the image:</emphasis>
|
||||||
|
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 <filename>bitbake</filename>
|
||||||
|
command.</para></listitem>
|
||||||
|
</orderedlist>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='tip-dirty-string'>
|
||||||
|
<title>"-dirty" String</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git status
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
To brute force pickup and commit all such pending changes, enter the following:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git add .
|
||||||
|
$ git commit -s -a -m "getting rid of -dirty"
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Next, rebuild the kernel.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
</chapter>
|
||||||
|
<!--
|
||||||
|
vim: expandtab tw=80 ts=4
|
||||||
|
-->
|
|
@ -0,0 +1,392 @@
|
||||||
|
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
|
||||||
|
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
|
||||||
|
[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
|
||||||
|
|
||||||
|
<chapter id='kernel-concepts'>
|
||||||
|
|
||||||
|
<title>Yocto Project Kernel Concepts</title>
|
||||||
|
|
||||||
|
<section id='concepts-org'>
|
||||||
|
<title>Introduction</title>
|
||||||
|
<para>
|
||||||
|
This chapter provides conceptual information about the kernel:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>Kernel Goals</para></listitem>
|
||||||
|
<listitem><para>Kernel Development and Maintenance Overview</para></listitem>
|
||||||
|
<listitem><para>Kernel Architecture</para></listitem>
|
||||||
|
<listitem><para>Kernel Tools</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='kernel-goals'>
|
||||||
|
<title>Kernel Goals</title>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
With all these considerations in mind, the Yocto Project's kernel and development team
|
||||||
|
strives to attain these goals:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>Allow the end user to leverage community best practices to seamlessly
|
||||||
|
manage the development, build and debug cycles.</para></listitem>
|
||||||
|
<listitem><para>Create a platform for performing integration and collaboration with the
|
||||||
|
thousands of upstream development projects that exist.</para></listitem>
|
||||||
|
<listitem><para>Provide mechanisms that support many different work flows, front-ends and
|
||||||
|
management techniques.</para></listitem>
|
||||||
|
<listitem><para>Deliver the most up-to-date kernel possible while still ensuring that
|
||||||
|
the baseline kernel is the most stable official release.</para></listitem>
|
||||||
|
<listitem><para>Include major technological features as part of the Yocto Project's
|
||||||
|
upward revision strategy.</para></listitem>
|
||||||
|
<listitem><para>Present a kernel Git repository that, similar to the upstream
|
||||||
|
<filename>kernel.org</filename> tree,
|
||||||
|
has a clear and continuous history.</para></listitem>
|
||||||
|
<listitem><para>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).</para></listitem>
|
||||||
|
<listitem><para>Employ a Git branching strategy that, from a developer's point of view,
|
||||||
|
results in a linear path from the baseline <filename>kernel.org</filename>,
|
||||||
|
through a select group of features and
|
||||||
|
ends with their BSP-specific commits.</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='kernel-big-picture'>
|
||||||
|
<title>Yocto Project Kernel Development and Maintenance Overview</title>
|
||||||
|
<para>
|
||||||
|
Kernels available through the Yocto Project, like other kernels, are based off the Linux
|
||||||
|
kernel releases from <ulink url='http://www.kernel.org'></ulink>.
|
||||||
|
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 <filename>kernel.org</filename> 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
|
||||||
|
<filename>kernel.org</filename> final release will clearly be within the early stages of
|
||||||
|
the Yocto Project development window.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
This balance allows the team to deliver the most up-to-date kernel
|
||||||
|
possible, while still ensuring that the team has a stable official release for
|
||||||
|
the baseline Linux kernel version.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
The ultimate source for kernels available through the Yocto Project are released kernels
|
||||||
|
from <filename>kernel.org</filename>.
|
||||||
|
In addition to a foundational kernel from <filename>kernel.org</filename>, 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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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 <filename>kernel.org</filename> 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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='kernel-architecture'>
|
||||||
|
<title>Kernel Architecture</title>
|
||||||
|
<para>
|
||||||
|
This section describes the architecture of the kernels available through the
|
||||||
|
Yocto Project and provides information
|
||||||
|
on the mechanisms used to achieve that architecture.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<section id='architecture-overview'>
|
||||||
|
<title>Overview</title>
|
||||||
|
<para>
|
||||||
|
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 <filename>kernel.org</filename>.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#git'>Git</ulink>" section in the
|
||||||
|
Yocto Project Development Manual.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
The following illustration shows the conceptual Yocto Project kernel.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
<imagedata fileref="figures/kernel-architecture-overview.png" width="6in" depth="7in" align="center" scale="100" />
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='branching-and-workflow'>
|
||||||
|
<title>Branching Strategy and Workflow</title>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note>
|
||||||
|
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.
|
||||||
|
</note>
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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 <filename>kernel.org</filename>, 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 <filename>diff</filename> level is now a trivial operation.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='source-code-manager-git'>
|
||||||
|
<title>Source Code Manager - Git</title>
|
||||||
|
<para>
|
||||||
|
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 <filename>kernel.org</filename> but,
|
||||||
|
Git continues to grow in popularity and supports many different work flows,
|
||||||
|
front-ends and management techniques.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
You can find documentation on Git at <ulink url='http://git-scm.com/documentation'></ulink>.
|
||||||
|
You can also get an introduction to Git as it applies to the Yocto Project in the
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#git'>Git</ulink>"
|
||||||
|
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.
|
||||||
|
<note>
|
||||||
|
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.
|
||||||
|
</note>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='kernel-configuration'>
|
||||||
|
<title>Kernel Configuration</title>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 <filename>.config</filename> file, which
|
||||||
|
is created through the Linux Kernel Configuration (LKC) tool.
|
||||||
|
You can directly set various configurations in the
|
||||||
|
<filename>.config</filename> file by using the <filename>menuconfig</filename>
|
||||||
|
tool as built by BitBake.
|
||||||
|
You can also define configurations in the file by using configuration fragments.
|
||||||
|
<note>
|
||||||
|
It is not recommended that you edit the <filename>.config</filename> file directly.
|
||||||
|
</note>
|
||||||
|
Here are some brief descriptions of the ways you can affect the
|
||||||
|
<filename>.config</filename> file:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para><emphasis>The <filename>menuconfig</filename> Tool:</emphasis>
|
||||||
|
One of many front-ends that allows you to define kernel configurations.
|
||||||
|
Some others are <filename>make config</filename>,
|
||||||
|
<filename>make nconfig</filename>, and <filename>make gconfig</filename>.
|
||||||
|
In the Yocto Project environment, you must use BitBake to build the
|
||||||
|
<filename>menuconfig</filename> tool before you can use it to define
|
||||||
|
configurations:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ bitbake linux-yocto -c menuconfig
|
||||||
|
</literallayout>
|
||||||
|
After the tool is built, you can interact with it normally.
|
||||||
|
You can see how <filename>menuconfig</filename> is used to change a simple
|
||||||
|
kernel configuration in the
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#configuring-the-kernel'>Configuring the Kernel</ulink>"
|
||||||
|
section of the Yocto Project Development Manual.
|
||||||
|
For general information on <filename>menuconfig</filename>, see
|
||||||
|
<ulink url='http://en.wikipedia.org/wiki/Menuconfig'></ulink>.
|
||||||
|
</para></listitem>
|
||||||
|
<listitem><para><emphasis>Configuration Fragments:</emphasis> A file with a
|
||||||
|
list of kernel options just as they would appear syntactically in the
|
||||||
|
<filename>.config</filename> 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 <filename>.config</filename> file.</para>
|
||||||
|
<para>The
|
||||||
|
<filename><ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_FEATURES'>KERNEL_FEATURES</ulink></filename>
|
||||||
|
variable can be used to list configuration fragments.
|
||||||
|
For further discussion on applying configuration fragments, see the
|
||||||
|
"<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-filelayout-kernel'>Linux Kernel Configuration</ulink>"
|
||||||
|
section in the Yocto Project Board Support Package (BSP) Guide.
|
||||||
|
</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='kernel-tools'>
|
||||||
|
<title>Kernel Tools</title>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
Fundamentally, the kernel tools that manage and construct the
|
||||||
|
Yocto Project kernel accomplish the following:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>Group patches into named, reusable features.</para></listitem>
|
||||||
|
<listitem><para>Allow top-down control of included features.</para></listitem>
|
||||||
|
<listitem><para>Bind kernel configurations to kernel patches and features.</para></listitem>
|
||||||
|
<listitem><para>Present a seamless Git repository that blends Yocto Project value
|
||||||
|
with the <filename>kernel.org</filename> history and development.</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</chapter>
|
||||||
|
<!--
|
||||||
|
vim: expandtab tw=80 ts=4
|
||||||
|
-->
|
|
@ -0,0 +1,8 @@
|
||||||
|
<?xml version='1.0'?>
|
||||||
|
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns="http://www.w3.org/1999/xhtml" xmlns:fo="http://www.w3.org/1999/XSL/Format" version="1.0">
|
||||||
|
|
||||||
|
<xsl:import href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl" />
|
||||||
|
|
||||||
|
<!-- <xsl:param name="generate.toc" select="'article nop'"></xsl:param> -->
|
||||||
|
|
||||||
|
</xsl:stylesheet>
|
|
@ -0,0 +1,918 @@
|
||||||
|
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
|
||||||
|
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
|
||||||
|
[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
|
||||||
|
|
||||||
|
<chapter id='kernel-how-to'>
|
||||||
|
|
||||||
|
<title>Working with the Yocto Project Kernel</title>
|
||||||
|
|
||||||
|
|
||||||
|
<section id='actions-org'>
|
||||||
|
<title>Introduction</title>
|
||||||
|
<para>
|
||||||
|
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:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>Tree construction</para></listitem>
|
||||||
|
<listitem><para>Build strategies</para></listitem>
|
||||||
|
<listitem><para>Workflow examples</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='tree-construction'>
|
||||||
|
<title>Tree Construction</title>
|
||||||
|
<para>
|
||||||
|
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
|
||||||
|
<ulink url='&YOCTO_GIT_URL;/cgit.cgi'>&YOCTO_GIT_URL;/cgit.cgi</ulink>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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 <filename>linux.org</filename> version 3.4:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git clone git://git.yoctoproject.org/linux-yocto-3.4
|
||||||
|
</literallayout>
|
||||||
|
For another example of how to set up a local Git repository of the Yocto Project
|
||||||
|
kernel files, see the
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#local-kernel-files'>Yocto Project Kernel</ulink>" bulleted
|
||||||
|
item in the Yocto Project Development Manual.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
Once you have cloned the kernel Git repository on your local machine, you can
|
||||||
|
switch to the <filename>meta</filename> branch within the repository.
|
||||||
|
Here is an example that assumes the local Git repository for the kernel is in
|
||||||
|
a top-level directory named <filename>linux-yocto-3.4</filename>:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ cd ~/linux-yocto-3.4
|
||||||
|
$ git checkout -b meta origin/meta
|
||||||
|
</literallayout>
|
||||||
|
Once you have checked out and switched to the <filename>meta</filename> 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 <filename>.scc</filename> files.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note>
|
||||||
|
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.
|
||||||
|
</note>
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
The following steps describe what happens when the Yocto Project Team constructs
|
||||||
|
the Yocto Project kernel source Git repository (or tree) found at
|
||||||
|
<ulink url='&YOCTO_GIT_URL;/cgit.cgi'></ulink> 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:
|
||||||
|
<orderedlist>
|
||||||
|
<listitem><para>A top-level kernel feature is passed to the kernel build subsystem.
|
||||||
|
Normally, this feature is a BSP for a particular kernel type.</para></listitem>
|
||||||
|
<listitem><para>The file that describes the top-level feature is located by searching
|
||||||
|
these system directories:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>The in-tree kernel-cache directories, which are located
|
||||||
|
in <filename>meta/cfg/kernel-cache</filename></para></listitem>
|
||||||
|
<listitem><para>Areas pointed to by <filename>SRC_URI</filename> statements
|
||||||
|
found in recipes</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
For a typical build, the target of the search is a
|
||||||
|
feature description in an <filename>.scc</filename> file
|
||||||
|
whose name follows this format:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
<bsp_name>-<kernel_type>.scc
|
||||||
|
</literallayout>
|
||||||
|
</para></listitem>
|
||||||
|
<listitem><para>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.</para></listitem>
|
||||||
|
<listitem><para>Extra features are appended to the top-level feature description.
|
||||||
|
These features can come from the
|
||||||
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_FEATURES'><filename>KERNEL_FEATURES</filename></ulink>
|
||||||
|
variable in recipes.</para></listitem>
|
||||||
|
<listitem><para>Each extra feature is located, compiled and appended to the script
|
||||||
|
as described in step three.</para></listitem>
|
||||||
|
<listitem><para>The script is executed to produce a series of <filename>meta-*</filename>
|
||||||
|
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.</para></listitem>
|
||||||
|
<listitem><para>The base repository is cloned, and the actions
|
||||||
|
listed in the <filename>meta-*</filename> directories are applied to the
|
||||||
|
tree.</para></listitem>
|
||||||
|
<listitem><para>The Git repository is left with the desired branch checked out and any
|
||||||
|
required branching, patching and tagging has been performed.</para></listitem>
|
||||||
|
</orderedlist>
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note><para>The generated <filename>meta-*</filename> 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
|
||||||
|
<ulink url='&YOCTO_GIT_URL;/cgit.cgi'>http://git.yoctoproject.org/cgit.cgi</ulink>
|
||||||
|
is the combination of all supported boards and configurations.</para>
|
||||||
|
<para>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.</para>
|
||||||
|
</note>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='build-strategy'>
|
||||||
|
<title>Build Strategy</title>
|
||||||
|
<para>
|
||||||
|
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:
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>The
|
||||||
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> points
|
||||||
|
to the kernel Git repository.</para></listitem>
|
||||||
|
<listitem><para>A BSP build branch exists.
|
||||||
|
This branch has the following form:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
<kernel_type>/<bsp_name>
|
||||||
|
</literallayout></para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 "<link linkend='workflow-examples'>Workflow Examples</link>".
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 <filename>.scc</filename>
|
||||||
|
files.
|
||||||
|
As the features are compiled, associated kernel configuration fragments are noted
|
||||||
|
and recorded in the <filename>meta-*</filename> series of directories in their compilation order.
|
||||||
|
The fragments are migrated, pre-processed and passed to the Linux Kernel
|
||||||
|
Configuration subsystem (<filename>lkc</filename>) as raw input in the form
|
||||||
|
of a <filename>.config</filename> file.
|
||||||
|
The <filename>lkc</filename> uses its own internal dependency constraints to do the final
|
||||||
|
processing of that information and generates the final <filename>.config</filename> file
|
||||||
|
that is used during compilation.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Using the board's architecture and other relevant values from the board's template,
|
||||||
|
kernel compilation is started and a kernel image is produced.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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
|
||||||
|
<filename>${MACHINE}</filename> is the metadata name of the machine (BSP) and "kernel_type" is one
|
||||||
|
of the Yocto Project supported kernel types (e.g. "standard"):
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
linux-${MACHINE}-<kernel_type>-build
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The existing support in the <filename>kernel.org</filename> tree achieves this
|
||||||
|
default functionality.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 <filename>.config</filename> file, all the <filename>.o</filename>
|
||||||
|
files, the <filename>.a</filename> 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.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='workflow-examples'>
|
||||||
|
<title>Workflow Examples</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
This section contains several workflow examples.
|
||||||
|
Many of the examples use Git commands.
|
||||||
|
You can find Git documentation at
|
||||||
|
<ulink url='http://git-scm.com/documentation'></ulink>.
|
||||||
|
You can find a simple overview of using Git with the Yocto Project in the
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#git'>Git</ulink>"
|
||||||
|
section of the Yocto Project Development Manual.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<section id='change-inspection-kernel-changes-commits'>
|
||||||
|
<title>Change Inspection: Changes/Commits</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
A common question when working with a kernel is:
|
||||||
|
"What changes have been applied to this tree?"
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<section id='what-changed-in-a-kernel'>
|
||||||
|
<title>What Changed in a Kernel?</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note>
|
||||||
|
In the following examples, unless you provide a commit range,
|
||||||
|
<filename>kernel.org</filename> 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
|
||||||
|
<ulink url='http://git.yoctoproject.org/cgit.cgi'></ulink>.
|
||||||
|
For example, the branch names for the <filename>linux-yocto-3.4</filename>
|
||||||
|
kernel repository can be seen at
|
||||||
|
<ulink url='http://git.yoctoproject.org/cgit.cgi/linux-yocto-3.4/refs/heads'></ulink>.
|
||||||
|
</note>
|
||||||
|
To see a full range of the changes, use the
|
||||||
|
<filename>git whatchanged</filename> command and specify a commit range
|
||||||
|
for the branch (<filename><commit>..<commit></filename>).
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Here is an example that looks at what has changed in the
|
||||||
|
<filename>emenlow</filename> branch of the
|
||||||
|
<filename>linux-yocto-3.4</filename> kernel.
|
||||||
|
The lower commit range is the commit associated with the
|
||||||
|
<filename>standard/base</filename> branch, while
|
||||||
|
the upper commit range is the commit associated with the
|
||||||
|
<filename>standard/emenlow</filename> branch.
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git whatchanged origin/standard/base..origin/standard/emenlow
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
To see a summary of changes use the <filename>git log</filename> command.
|
||||||
|
Here is an example using the same branches:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git log --oneline origin/standard/base..origin/standard/emenlow
|
||||||
|
</literallayout>
|
||||||
|
The <filename>git log</filename> output might be more useful than
|
||||||
|
the <filename>git whatchanged</filename> as you get
|
||||||
|
a short, one-line summary of each change and not the entire commit.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
If you want to see code differences associated with all the changes, use
|
||||||
|
the <filename>git diff</filename> command.
|
||||||
|
Here is an example:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git diff origin/standard/base..origin/standard/emenlow
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
You can see the commit log messages and the text differences using the
|
||||||
|
<filename>git show</filename> command:
|
||||||
|
Here is an example:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git show origin/standard/base..origin/standard/emenlow
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
You can create individual patches for each change by using the
|
||||||
|
<filename>git format-patch</filename> command.
|
||||||
|
Here is an example that that creates patch files for each commit and
|
||||||
|
places them in your <filename>Documents</filename> directory:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git format-patch -o $HOME/Documents origin/standard/base..origin/standard/emenlow
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='show-a-particular-feature-or-branch-change'>
|
||||||
|
<title>Show a Particular Feature or Branch Change</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note>
|
||||||
|
Because BSP branch, <filename>kernel.org</filename>, and feature tags are all
|
||||||
|
present, there could be many tags.
|
||||||
|
</note>
|
||||||
|
The <filename>git show <tag></filename> command shows changes that are tagged by
|
||||||
|
a feature.
|
||||||
|
Here is an example that shows changes tagged by the <filename>systemtap</filename>
|
||||||
|
feature:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git show systemtap
|
||||||
|
</literallayout>
|
||||||
|
You can use the <filename>git branch --contains <tag></filename> command
|
||||||
|
to show the branches that contain a particular feature.
|
||||||
|
This command shows the branches that contain the <filename>systemtap</filename>
|
||||||
|
feature:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git branch --contains systemtap
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
You can use many other comparisons to isolate BSP and kernel changes.
|
||||||
|
For example, you can compare against <filename>kernel.org</filename> tags
|
||||||
|
such as the <filename>v3.4</filename> tag.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='development-saving-kernel-modifications'>
|
||||||
|
<title>Development: Saving Kernel Modifications</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
This section and its sub-sections, describe general application of Git's
|
||||||
|
<filename>push</filename> and <filename>pull</filename> 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
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#pushing-a-change-upstream'>Using Scripts to Push a Change
|
||||||
|
Upstream and Request a Pull</ulink>" and
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#submitting-a-patch'>Using Email to Submit a Patch</ulink>"
|
||||||
|
sections in the Yocto Project Development Manual.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
There are many ways to save kernel modifications.
|
||||||
|
The technique employed
|
||||||
|
depends on the destination for the patches:
|
||||||
|
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>Bulk storage</para></listitem>
|
||||||
|
<listitem><para>Internal sharing either through patches or by using Git</para></listitem>
|
||||||
|
<listitem><para>External submissions</para></listitem>
|
||||||
|
<listitem><para>Exporting for integration into another Source Code
|
||||||
|
Manager (SCM)</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Because of the following list of issues, the destination of the patches also influences
|
||||||
|
the method for gathering them:
|
||||||
|
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>Bisectability</para></listitem>
|
||||||
|
<listitem><para>Commit headers</para></listitem>
|
||||||
|
<listitem><para>Division of subsystems for separate submission or review</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<section id='bulk-export'>
|
||||||
|
<title>Bulk Export</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note>
|
||||||
|
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.
|
||||||
|
</note>
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# bulk export of ALL modifications without separation or division
|
||||||
|
# of the changes
|
||||||
|
|
||||||
|
$ git add .
|
||||||
|
$ git commit -s -a -m <msg>
|
||||||
|
or
|
||||||
|
$ git commit -s -a # and interact with $EDITOR
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Once the changes are exported, you can restore them manually using a template
|
||||||
|
or through integration with the <filename>default_kernel</filename>.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='incremental-planned-sharing'>
|
||||||
|
<title>Incremental/Planned Sharing</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
During development, the following commands are of interest.
|
||||||
|
For full Git documentation, refer to the Git documentation at
|
||||||
|
<ulink url='http://github.com'></ulink>.
|
||||||
|
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# edit a file
|
||||||
|
$ vi <path>/file
|
||||||
|
# stage the change
|
||||||
|
$ git add <path>/file
|
||||||
|
# commit the change
|
||||||
|
$ git commit -s
|
||||||
|
# remove a file
|
||||||
|
$ git rm <path>/file
|
||||||
|
# commit the change
|
||||||
|
$ git commit -s
|
||||||
|
|
||||||
|
... etc.
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 <filename>push</filename> and
|
||||||
|
<filename>pull</filename> operations for
|
||||||
|
distributed development, you should consider the ramifications of changing a
|
||||||
|
commit that you have already shared with others.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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:
|
||||||
|
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ Git add <path>/file
|
||||||
|
$ Git commit --amend
|
||||||
|
$ Git rebase or Git rebase -i
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Again, assuming that the changes have not been pushed upstream, and that
|
||||||
|
no pending works-in-progress exist (use <filename>git status</filename> to check), then
|
||||||
|
you can revert (undo) commits by using the following commands:
|
||||||
|
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# 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^
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 <filename>push</filename> or <filename>pull</filename> 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 <filename>kernel.org</filename> best
|
||||||
|
practices, which is recommended.
|
||||||
|
<note>
|
||||||
|
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.
|
||||||
|
</note>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<section id='export-internally-via-patches'>
|
||||||
|
<title>Exporting Changes Internally by Using Patches</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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
|
||||||
|
<filename>git am</filename> command to reproduce the original commit and all
|
||||||
|
the related information such as author, date, commit log, and so forth.
|
||||||
|
<note>
|
||||||
|
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.
|
||||||
|
</note>
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# <first-commit> 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 <dir> <first commit>..<last commit>
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
In other words:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# Identify commits of interest.
|
||||||
|
|
||||||
|
# If the tree was tagged before development
|
||||||
|
$ git format-patch -o <save dir> <tag>
|
||||||
|
|
||||||
|
# If no tags are available
|
||||||
|
$ git format-patch -o <save dir> HEAD^ # last commit
|
||||||
|
$ git format-patch -o <save dir> HEAD^^ # last 2 commits
|
||||||
|
$ git whatchanged # identify last commit
|
||||||
|
$ git format-patch -o <save dir> <commit id>
|
||||||
|
$ git format-patch -o <save dir> <rev-list>
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='export-internally-via-git'>
|
||||||
|
<title>Exporting Changes Internally by Using Git</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Use this command form to push the changes:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git push ssh://<master_server>/<path_to_repo>
|
||||||
|
<local_branch>:<remote_branch>
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
For example, the following command pushes the changes from your local branch
|
||||||
|
<filename>yocto/standard/common-pc/base</filename> to the remote branch with the same name
|
||||||
|
in the master repository <filename>//git.mycompany.com/pub/git/kernel-3.4</filename>.
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git push ssh://git.mycompany.com/pub/git/kernel-3.4 \
|
||||||
|
yocto/standard/common-pc/base:yocto/standard/common-pc/base
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
A pull request entails using the <filename>git request-pull</filename> command to compose
|
||||||
|
an email to the
|
||||||
|
maintainer requesting that a branch be pulled into the master repository, see
|
||||||
|
<ulink url='http://github.com/guides/pull-requests'></ulink> for an example.
|
||||||
|
<note>
|
||||||
|
Other commands such as <filename>git stash</filename> or branching can also be used to save
|
||||||
|
changes, but are not covered in this document.
|
||||||
|
</note>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='export-for-external-upstream-submission'>
|
||||||
|
<title>Exporting Changes for External (Upstream) Submission</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note>
|
||||||
|
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:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>
|
||||||
|
<ulink url='http://linux.yyz.us/patch-format.html'></ulink></para></listitem>
|
||||||
|
<listitem><para>Documentation/SubmittingPatches (in any linux
|
||||||
|
kernel source tree)</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</note>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#how-to-submit-a-change'>How to Submit a
|
||||||
|
Change</ulink>" section in the Yocto Project Development Manual.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
If the initial commits were not properly documented or do not meet those standards,
|
||||||
|
you can re-base by using the <filename>git rebase -i</filename> 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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 <filename>git send-email</filename> is commonly used to ensure
|
||||||
|
that patches are properly
|
||||||
|
formatted for easy application and avoid mailer-induced patch damage.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The following is an example of dumping patches for external submission:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# dump the last 4 commits
|
||||||
|
$ git format-patch --thread -n -o ~/rr/ HEAD^^^^
|
||||||
|
$ git send-email --compose --subject '[RFC 0/N] <patch series summary>' \
|
||||||
|
--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
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='export-for-import-into-other-scm'>
|
||||||
|
<title>Exporting Changes for Import into Another SCM</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='scm-working-with-the-yocto-project-kernel-in-another-scm'>
|
||||||
|
<title>Working with the Yocto Project Kernel in Another SCM</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>The delivered Yocto Project kernel must be exported into the second
|
||||||
|
SCM.</para></listitem>
|
||||||
|
<listitem><para>Development must be exported from that secondary SCM into a
|
||||||
|
format that can be used by the OpenEmbedded build system.</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<section id='exporting-delivered-kernel-to-scm'>
|
||||||
|
<title>Exporting the Delivered Kernel to the SCM</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The following commands illustrate some of the steps you could use to
|
||||||
|
import the <filename>yocto/standard/common-pc/base</filename>
|
||||||
|
kernel into a secondary SCM:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git checkout yocto/standard/common-pc/base
|
||||||
|
$ cd .. ; echo linux/.git > .cvsignore
|
||||||
|
$ cvs import -m "initial import" linux MY_COMPANY start
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
You could now relocate the CVS repository and use it in a centralized manner.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The following commands illustrate how you can condense and merge two BSPs into a
|
||||||
|
second SCM:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ 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 > .cvsignore
|
||||||
|
$ cvs import -m "initial import" linux MY_COMPANY start
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='importing-changes-for-build'>
|
||||||
|
<title>Importing Changes for the Build</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='bsp-creating'>
|
||||||
|
<title>Creating a BSP Based on an Existing Similar BSP</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 new BSP, see
|
||||||
|
the "<ulink url='&YOCTO_DOCS_BSP_URL;#creating-a-new-bsp-layer-using-the-yocto-bsp-script'>Creating a New BSP Layer Using the yocto-bsp Script</ulink>" section in the
|
||||||
|
Yocto Project Board Support Package (BSP) Developer's Guide, or see the
|
||||||
|
<ulink url='&YOCTO_WIKI_URL;/wiki/Transcript:_creating_one_generic_Atom_BSP_from_another'>Transcript:_creating_one_generic_Atom_BSP_from_another</ulink>
|
||||||
|
wiki page.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The basic steps you need to follow are:
|
||||||
|
<orderedlist>
|
||||||
|
<listitem><para><emphasis>Make sure you have set up a local Source Directory:</emphasis>
|
||||||
|
You must create a local
|
||||||
|
<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>
|
||||||
|
by either creating a Git repository (recommended) or
|
||||||
|
extracting a Yocto Project release tarball.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Choose an existing BSP available with the Yocto Project:</emphasis>
|
||||||
|
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
|
||||||
|
<ulink url='&YOCTO_HOME_URL;/download'></ulink>.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Be sure you have the Base BSP:</emphasis>
|
||||||
|
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.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Make a copy of the existing BSP, thus isolating your new
|
||||||
|
BSP work:</emphasis>
|
||||||
|
Copying the existing BSP file structure gives you a new area in which to work.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Make configuration and recipe changes to your new BSP:</emphasis>
|
||||||
|
Configuration changes involve the files in the BSP's <filename>conf</filename>
|
||||||
|
directory.
|
||||||
|
Changes include creating a machine-specific configuration file and editing the
|
||||||
|
<filename>layer.conf</filename> 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.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Prepare for the build:</emphasis>
|
||||||
|
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 <filename>local.conf</filename> and <filename>bblayers.conf</filename>
|
||||||
|
files.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Build the image:</emphasis>
|
||||||
|
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 <filename>bitbake</filename>
|
||||||
|
command.</para></listitem>
|
||||||
|
</orderedlist>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='tip-dirty-string'>
|
||||||
|
<title>"-dirty" String</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git status
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
To brute force pickup and commit all such pending changes, enter the following:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git add .
|
||||||
|
$ git commit -s -a -m "getting rid of -dirty"
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Next, rebuild the kernel.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
</chapter>
|
||||||
|
<!--
|
||||||
|
vim: expandtab tw=80 ts=4
|
||||||
|
-->
|
|
@ -0,0 +1,918 @@
|
||||||
|
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
|
||||||
|
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
|
||||||
|
[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
|
||||||
|
|
||||||
|
<chapter id='kernel-how-to'>
|
||||||
|
|
||||||
|
<title>Working with the Yocto Project Kernel</title>
|
||||||
|
|
||||||
|
|
||||||
|
<section id='actions-org'>
|
||||||
|
<title>Introduction</title>
|
||||||
|
<para>
|
||||||
|
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:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>Tree construction</para></listitem>
|
||||||
|
<listitem><para>Build strategies</para></listitem>
|
||||||
|
<listitem><para>Workflow examples</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='tree-construction'>
|
||||||
|
<title>Tree Construction</title>
|
||||||
|
<para>
|
||||||
|
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
|
||||||
|
<ulink url='&YOCTO_GIT_URL;/cgit.cgi'>&YOCTO_GIT_URL;/cgit.cgi</ulink>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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 <filename>linux.org</filename> version 3.4:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git clone git://git.yoctoproject.org/linux-yocto-3.4
|
||||||
|
</literallayout>
|
||||||
|
For another example of how to set up a local Git repository of the Yocto Project
|
||||||
|
kernel files, see the
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#local-kernel-files'>Yocto Project Kernel</ulink>" bulleted
|
||||||
|
item in the Yocto Project Development Manual.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
Once you have cloned the kernel Git repository on your local machine, you can
|
||||||
|
switch to the <filename>meta</filename> branch within the repository.
|
||||||
|
Here is an example that assumes the local Git repository for the kernel is in
|
||||||
|
a top-level directory named <filename>linux-yocto-3.4</filename>:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ cd ~/linux-yocto-3.4
|
||||||
|
$ git checkout -b meta origin/meta
|
||||||
|
</literallayout>
|
||||||
|
Once you have checked out and switched to the <filename>meta</filename> 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 <filename>.scc</filename> files.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note>
|
||||||
|
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.
|
||||||
|
</note>
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
The following steps describe what happens when the Yocto Project Team constructs
|
||||||
|
the Yocto Project kernel source Git repository (or tree) found at
|
||||||
|
<ulink url='&YOCTO_GIT_URL;/cgit.cgi'></ulink> 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:
|
||||||
|
<orderedlist>
|
||||||
|
<listitem><para>A top-level kernel feature is passed to the kernel build subsystem.
|
||||||
|
Normally, this feature is a BSP for a particular kernel type.</para></listitem>
|
||||||
|
<listitem><para>The file that describes the top-level feature is located by searching
|
||||||
|
these system directories:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>The in-tree kernel-cache directories, which are located
|
||||||
|
in <filename>meta/cfg/kernel-cache</filename></para></listitem>
|
||||||
|
<listitem><para>Areas pointed to by <filename>SRC_URI</filename> statements
|
||||||
|
found in recipes</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
For a typical build, the target of the search is a
|
||||||
|
feature description in an <filename>.scc</filename> file
|
||||||
|
whose name follows this format:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
<bsp_name>-<kernel_type>.scc
|
||||||
|
</literallayout>
|
||||||
|
</para></listitem>
|
||||||
|
<listitem><para>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.</para></listitem>
|
||||||
|
<listitem><para>Extra features are appended to the top-level feature description.
|
||||||
|
These features can come from the
|
||||||
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_FEATURES'><filename>KERNEL_FEATURES</filename></ulink>
|
||||||
|
variable in recipes.</para></listitem>
|
||||||
|
<listitem><para>Each extra feature is located, compiled and appended to the script
|
||||||
|
as described in step three.</para></listitem>
|
||||||
|
<listitem><para>The script is executed to produce a series of <filename>meta-*</filename>
|
||||||
|
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.</para></listitem>
|
||||||
|
<listitem><para>The base repository is cloned, and the actions
|
||||||
|
listed in the <filename>meta-*</filename> directories are applied to the
|
||||||
|
tree.</para></listitem>
|
||||||
|
<listitem><para>The Git repository is left with the desired branch checked out and any
|
||||||
|
required branching, patching and tagging has been performed.</para></listitem>
|
||||||
|
</orderedlist>
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note><para>The generated <filename>meta-*</filename> 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
|
||||||
|
<ulink url='&YOCTO_GIT_URL;/cgit.cgi'>http://git.yoctoproject.org/cgit.cgi</ulink>
|
||||||
|
is the combination of all supported boards and configurations.</para>
|
||||||
|
<para>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.</para>
|
||||||
|
</note>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='build-strategy'>
|
||||||
|
<title>Build Strategy</title>
|
||||||
|
<para>
|
||||||
|
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:
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>The
|
||||||
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> points
|
||||||
|
to the kernel Git repository.</para></listitem>
|
||||||
|
<listitem><para>A BSP build branch exists.
|
||||||
|
This branch has the following form:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
<kernel_type>/<bsp_name>
|
||||||
|
</literallayout></para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 "<link linkend='workflow-examples'>Workflow Examples</link>".
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 <filename>.scc</filename>
|
||||||
|
files.
|
||||||
|
As the features are compiled, associated kernel configuration fragments are noted
|
||||||
|
and recorded in the <filename>meta-*</filename> series of directories in their compilation order.
|
||||||
|
The fragments are migrated, pre-processed and passed to the Linux Kernel
|
||||||
|
Configuration subsystem (<filename>lkc</filename>) as raw input in the form
|
||||||
|
of a <filename>.config</filename> file.
|
||||||
|
The <filename>lkc</filename> uses its own internal dependency constraints to do the final
|
||||||
|
processing of that information and generates the final <filename>.config</filename> file
|
||||||
|
that is used during compilation.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Using the board's architecture and other relevant values from the board's template,
|
||||||
|
kernel compilation is started and a kernel image is produced.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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
|
||||||
|
<filename>${MACHINE}</filename> is the metadata name of the machine (BSP) and "kernel_type" is one
|
||||||
|
of the Yocto Project supported kernel types (e.g. "standard"):
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
linux-${MACHINE}-<kernel_type>-build
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The existing support in the <filename>kernel.org</filename> tree achieves this
|
||||||
|
default functionality.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 <filename>.config</filename> file, all the <filename>.o</filename>
|
||||||
|
files, the <filename>.a</filename> 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.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='workflow-examples'>
|
||||||
|
<title>Workflow Examples</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
This section contains several workflow examples.
|
||||||
|
Many of the examples use Git commands.
|
||||||
|
You can find Git documentation at
|
||||||
|
<ulink url='http://git-scm.com/documentation'></ulink>.
|
||||||
|
You can find a simple overview of using Git with the Yocto Project in the
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#git'>Git</ulink>"
|
||||||
|
section of the Yocto Project Development Manual.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<section id='change-inspection-kernel-changes-commits'>
|
||||||
|
<title>Change Inspection: Changes/Commits</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
A common question when working with a kernel is:
|
||||||
|
"What changes have been applied to this tree?"
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<section id='what-changed-in-a-kernel'>
|
||||||
|
<title>What Changed in a Kernel?</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note>
|
||||||
|
In the following examples, unless you provide a commit range,
|
||||||
|
<filename>kernel.org</filename> 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
|
||||||
|
<ulink url='http://git.yoctoproject.org/cgit.cgi'></ulink>.
|
||||||
|
For example, the branch names for the <filename>linux-yocto-3.4</filename>
|
||||||
|
kernel repository can be seen at
|
||||||
|
<ulink url='http://git.yoctoproject.org/cgit.cgi/linux-yocto-3.4/refs/heads'></ulink>.
|
||||||
|
</note>
|
||||||
|
To see a full range of the changes, use the
|
||||||
|
<filename>git whatchanged</filename> command and specify a commit range
|
||||||
|
for the branch (<filename><commit>..<commit></filename>).
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Here is an example that looks at what has changed in the
|
||||||
|
<filename>emenlow</filename> branch of the
|
||||||
|
<filename>linux-yocto-3.4</filename> kernel.
|
||||||
|
The lower commit range is the commit associated with the
|
||||||
|
<filename>standard/base</filename> branch, while
|
||||||
|
the upper commit range is the commit associated with the
|
||||||
|
<filename>standard/emenlow</filename> branch.
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git whatchanged origin/standard/base..origin/standard/emenlow
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
To see a summary of changes use the <filename>git log</filename> command.
|
||||||
|
Here is an example using the same branches:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git log --oneline origin/standard/base..origin/standard/emenlow
|
||||||
|
</literallayout>
|
||||||
|
The <filename>git log</filename> output might be more useful than
|
||||||
|
the <filename>git whatchanged</filename> as you get
|
||||||
|
a short, one-line summary of each change and not the entire commit.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
If you want to see code differences associated with all the changes, use
|
||||||
|
the <filename>git diff</filename> command.
|
||||||
|
Here is an example:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git diff origin/standard/base..origin/standard/emenlow
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
You can see the commit log messages and the text differences using the
|
||||||
|
<filename>git show</filename> command:
|
||||||
|
Here is an example:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git show origin/standard/base..origin/standard/emenlow
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
You can create individual patches for each change by using the
|
||||||
|
<filename>git format-patch</filename> command.
|
||||||
|
Here is an example that that creates patch files for each commit and
|
||||||
|
places them in your <filename>Documents</filename> directory:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git format-patch -o $HOME/Documents origin/standard/base..origin/standard/emenlow
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='show-a-particular-feature-or-branch-change'>
|
||||||
|
<title>Show a Particular Feature or Branch Change</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note>
|
||||||
|
Because BSP branch, <filename>kernel.org</filename>, and feature tags are all
|
||||||
|
present, there could be many tags.
|
||||||
|
</note>
|
||||||
|
The <filename>git show <tag></filename> command shows changes that are tagged by
|
||||||
|
a feature.
|
||||||
|
Here is an example that shows changes tagged by the <filename>systemtap</filename>
|
||||||
|
feature:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git show systemtap
|
||||||
|
</literallayout>
|
||||||
|
You can use the <filename>git branch --contains <tag></filename> command
|
||||||
|
to show the branches that contain a particular feature.
|
||||||
|
This command shows the branches that contain the <filename>systemtap</filename>
|
||||||
|
feature:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git branch --contains systemtap
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
You can use many other comparisons to isolate BSP and kernel changes.
|
||||||
|
For example, you can compare against <filename>kernel.org</filename> tags
|
||||||
|
such as the <filename>v3.4</filename> tag.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='development-saving-kernel-modifications'>
|
||||||
|
<title>Development: Saving Kernel Modifications</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
This section and its sub-sections, describe general application of Git's
|
||||||
|
<filename>push</filename> and <filename>pull</filename> 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
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#pushing-a-change-upstream'>Using Scripts to Push a Change
|
||||||
|
Upstream and Request a Pull</ulink>" and
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#submitting-a-patch'>Using Email to Submit a Patch</ulink>"
|
||||||
|
sections in the Yocto Project Development Manual.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
There are many ways to save kernel modifications.
|
||||||
|
The technique employed
|
||||||
|
depends on the destination for the patches:
|
||||||
|
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>Bulk storage</para></listitem>
|
||||||
|
<listitem><para>Internal sharing either through patches or by using Git</para></listitem>
|
||||||
|
<listitem><para>External submissions</para></listitem>
|
||||||
|
<listitem><para>Exporting for integration into another Source Code
|
||||||
|
Manager (SCM)</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Because of the following list of issues, the destination of the patches also influences
|
||||||
|
the method for gathering them:
|
||||||
|
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>Bisectability</para></listitem>
|
||||||
|
<listitem><para>Commit headers</para></listitem>
|
||||||
|
<listitem><para>Division of subsystems for separate submission or review</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<section id='bulk-export'>
|
||||||
|
<title>Bulk Export</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note>
|
||||||
|
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.
|
||||||
|
</note>
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# bulk export of ALL modifications without separation or division
|
||||||
|
# of the changes
|
||||||
|
|
||||||
|
$ git add .
|
||||||
|
$ git commit -s -a -m <msg>
|
||||||
|
or
|
||||||
|
$ git commit -s -a # and interact with $EDITOR
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Once the changes are exported, you can restore them manually using a template
|
||||||
|
or through integration with the <filename>default_kernel</filename>.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='incremental-planned-sharing'>
|
||||||
|
<title>Incremental/Planned Sharing</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
During development, the following commands are of interest.
|
||||||
|
For full Git documentation, refer to the Git documentation at
|
||||||
|
<ulink url='http://github.com'></ulink>.
|
||||||
|
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# edit a file
|
||||||
|
$ vi <path>/file
|
||||||
|
# stage the change
|
||||||
|
$ git add <path>/file
|
||||||
|
# commit the change
|
||||||
|
$ git commit -s
|
||||||
|
# remove a file
|
||||||
|
$ git rm <path>/file
|
||||||
|
# commit the change
|
||||||
|
$ git commit -s
|
||||||
|
|
||||||
|
... etc.
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 <filename>push</filename> and
|
||||||
|
<filename>pull</filename> operations for
|
||||||
|
distributed development, you should consider the ramifications of changing a
|
||||||
|
commit that you have already shared with others.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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:
|
||||||
|
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ Git add <path>/file
|
||||||
|
$ Git commit --amend
|
||||||
|
$ Git rebase or Git rebase -i
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Again, assuming that the changes have not been pushed upstream, and that
|
||||||
|
no pending works-in-progress exist (use <filename>git status</filename> to check), then
|
||||||
|
you can revert (undo) commits by using the following commands:
|
||||||
|
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# 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^
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 <filename>push</filename> or <filename>pull</filename> 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 <filename>kernel.org</filename> best
|
||||||
|
practices, which is recommended.
|
||||||
|
<note>
|
||||||
|
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.
|
||||||
|
</note>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<section id='export-internally-via-patches'>
|
||||||
|
<title>Exporting Changes Internally by Using Patches</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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
|
||||||
|
<filename>git am</filename> command to reproduce the original commit and all
|
||||||
|
the related information such as author, date, commit log, and so forth.
|
||||||
|
<note>
|
||||||
|
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.
|
||||||
|
</note>
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# <first-commit> 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 <dir> <first commit>..<last commit>
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
In other words:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# Identify commits of interest.
|
||||||
|
|
||||||
|
# If the tree was tagged before development
|
||||||
|
$ git format-patch -o <save dir> <tag>
|
||||||
|
|
||||||
|
# If no tags are available
|
||||||
|
$ git format-patch -o <save dir> HEAD^ # last commit
|
||||||
|
$ git format-patch -o <save dir> HEAD^^ # last 2 commits
|
||||||
|
$ git whatchanged # identify last commit
|
||||||
|
$ git format-patch -o <save dir> <commit id>
|
||||||
|
$ git format-patch -o <save dir> <rev-list>
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='export-internally-via-git'>
|
||||||
|
<title>Exporting Changes Internally by Using Git</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Use this command form to push the changes:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git push ssh://<master_server>/<path_to_repo>
|
||||||
|
<local_branch>:<remote_branch>
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
For example, the following command pushes the changes from your local branch
|
||||||
|
<filename>yocto/standard/common-pc/base</filename> to the remote branch with the same name
|
||||||
|
in the master repository <filename>//git.mycompany.com/pub/git/kernel-3.4</filename>.
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git push ssh://git.mycompany.com/pub/git/kernel-3.4 \
|
||||||
|
yocto/standard/common-pc/base:yocto/standard/common-pc/base
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
A pull request entails using the <filename>git request-pull</filename> command to compose
|
||||||
|
an email to the
|
||||||
|
maintainer requesting that a branch be pulled into the master repository, see
|
||||||
|
<ulink url='http://github.com/guides/pull-requests'></ulink> for an example.
|
||||||
|
<note>
|
||||||
|
Other commands such as <filename>git stash</filename> or branching can also be used to save
|
||||||
|
changes, but are not covered in this document.
|
||||||
|
</note>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='export-for-external-upstream-submission'>
|
||||||
|
<title>Exporting Changes for External (Upstream) Submission</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<note>
|
||||||
|
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:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>
|
||||||
|
<ulink url='http://linux.yyz.us/patch-format.html'></ulink></para></listitem>
|
||||||
|
<listitem><para>Documentation/SubmittingPatches (in any linux
|
||||||
|
kernel source tree)</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</note>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#how-to-submit-a-change'>How to Submit a
|
||||||
|
Change</ulink>" section in the Yocto Project Development Manual.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
If the initial commits were not properly documented or do not meet those standards,
|
||||||
|
you can re-base by using the <filename>git rebase -i</filename> 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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 <filename>git send-email</filename> is commonly used to ensure
|
||||||
|
that patches are properly
|
||||||
|
formatted for easy application and avoid mailer-induced patch damage.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The following is an example of dumping patches for external submission:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
# dump the last 4 commits
|
||||||
|
$ git format-patch --thread -n -o ~/rr/ HEAD^^^^
|
||||||
|
$ git send-email --compose --subject '[RFC 0/N] <patch series summary>' \
|
||||||
|
--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
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='export-for-import-into-other-scm'>
|
||||||
|
<title>Exporting Changes for Import into Another SCM</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='scm-working-with-the-yocto-project-kernel-in-another-scm'>
|
||||||
|
<title>Working with the Yocto Project Kernel in Another SCM</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>The delivered Yocto Project kernel must be exported into the second
|
||||||
|
SCM.</para></listitem>
|
||||||
|
<listitem><para>Development must be exported from that secondary SCM into a
|
||||||
|
format that can be used by the OpenEmbedded build system.</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<section id='exporting-delivered-kernel-to-scm'>
|
||||||
|
<title>Exporting the Delivered Kernel to the SCM</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The following commands illustrate some of the steps you could use to
|
||||||
|
import the <filename>yocto/standard/common-pc/base</filename>
|
||||||
|
kernel into a secondary SCM:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git checkout yocto/standard/common-pc/base
|
||||||
|
$ cd .. ; echo linux/.git > .cvsignore
|
||||||
|
$ cvs import -m "initial import" linux MY_COMPANY start
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
You could now relocate the CVS repository and use it in a centralized manner.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The following commands illustrate how you can condense and merge two BSPs into a
|
||||||
|
second SCM:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ 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 > .cvsignore
|
||||||
|
$ cvs import -m "initial import" linux MY_COMPANY start
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='importing-changes-for-build'>
|
||||||
|
<title>Importing Changes for the Build</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='bsp-creating'>
|
||||||
|
<title>Creating a BSP Based on an Existing Similar BSP</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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 new BSP, see
|
||||||
|
the "<ulink url='&YOCTO_DOCS_BSP_URL;#creating-a-new-bsp-layer-using-the-yocto-bsp-script'>Creating a New BSP Layer Using the yocto-bsp Script</ulink>" section in the
|
||||||
|
Yocto Project Board Support Package (BSP) Developer's Guide, or see the
|
||||||
|
<ulink url='&YOCTO_WIKI_URL;/wiki/Transcript:_creating_one_generic_Atom_BSP_from_another'>Transcript:_creating_one_generic_Atom_BSP_from_another</ulink>
|
||||||
|
wiki page.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The basic steps you need to follow are:
|
||||||
|
<orderedlist>
|
||||||
|
<listitem><para><emphasis>Make sure you have set up a local Source Directory:</emphasis>
|
||||||
|
You must create a local
|
||||||
|
<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>
|
||||||
|
by either creating a Git repository (recommended) or
|
||||||
|
extracting a Yocto Project release tarball.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Choose an existing BSP available with the Yocto Project:</emphasis>
|
||||||
|
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
|
||||||
|
<ulink url='&YOCTO_HOME_URL;/download'></ulink>.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Be sure you have the Base BSP:</emphasis>
|
||||||
|
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.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Make a copy of the existing BSP, thus isolating your new
|
||||||
|
BSP work:</emphasis>
|
||||||
|
Copying the existing BSP file structure gives you a new area in which to work.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Make configuration and recipe changes to your new BSP:</emphasis>
|
||||||
|
Configuration changes involve the files in the BSP's <filename>conf</filename>
|
||||||
|
directory.
|
||||||
|
Changes include creating a machine-specific configuration file and editing the
|
||||||
|
<filename>layer.conf</filename> 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.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Prepare for the build:</emphasis>
|
||||||
|
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 <filename>local.conf</filename> and <filename>bblayers.conf</filename>
|
||||||
|
files.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Build the image:</emphasis>
|
||||||
|
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 <filename>bitbake</filename>
|
||||||
|
command.</para></listitem>
|
||||||
|
</orderedlist>
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
<section id='tip-dirty-string'>
|
||||||
|
<title>"-dirty" String</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git status
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
To brute force pickup and commit all such pending changes, enter the following:
|
||||||
|
<literallayout class='monospaced'>
|
||||||
|
$ git add .
|
||||||
|
$ git commit -s -a -m "getting rid of -dirty"
|
||||||
|
</literallayout>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Next, rebuild the kernel.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
</section>
|
||||||
|
</chapter>
|
||||||
|
<!--
|
||||||
|
vim: expandtab tw=80 ts=4
|
||||||
|
-->
|
|
@ -0,0 +1,78 @@
|
||||||
|
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
|
||||||
|
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
|
||||||
|
[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
|
||||||
|
|
||||||
|
<chapter id='kernel-doc-intro'>
|
||||||
|
|
||||||
|
<title>Yocto Project Kernel Architecture and Use Manual</title>
|
||||||
|
|
||||||
|
<section id='kernel-intro-section'>
|
||||||
|
<title>Introduction</title>
|
||||||
|
<para>
|
||||||
|
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.
|
||||||
|
</para>
|
||||||
|
<para>
|
||||||
|
This manual describes Yocto Project kernels by providing information
|
||||||
|
on history, organization, benefits, and use.
|
||||||
|
The manual consists of two sections:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para><emphasis>Concepts:</emphasis> 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.</para></listitem>
|
||||||
|
<listitem><para><emphasis>Using a Kernel:</emphasis> 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.</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
For more information on the Linux kernel, see the following links:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>The Linux Foundation's guide for kernel development
|
||||||
|
process - <ulink url='http://www.linuxfoundation.org/content/1-guide-kernel-development-process'></ulink></para></listitem>
|
||||||
|
<listitem><para>A fairly encompassing guide on Linux kernel development -
|
||||||
|
<ulink url='http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob_plain;f=Documentation/HOWTO;hb=HEAD'></ulink></para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
For more discussion on the Yocto Project kernel, you can see these sections
|
||||||
|
in the Yocto Project Development Manual:
|
||||||
|
<itemizedlist>
|
||||||
|
<listitem><para>
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#kernel-overview'>Kernel Overview</ulink>"</para></listitem>
|
||||||
|
<listitem><para>
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#kernel-modification-workflow'>Kernel Modification Workflow</ulink>"
|
||||||
|
</para></listitem>
|
||||||
|
<listitem><para>
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#patching-the-kernel'>Patching the Kernel</ulink>"</para></listitem>
|
||||||
|
<listitem><para>
|
||||||
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#configuring-the-kernel'>Configuring the Kernel</ulink>"</para></listitem>
|
||||||
|
</itemizedlist>
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
For general information on the Yocto Project, visit the website at
|
||||||
|
<ulink url='&YOCTO_HOME_URL;'></ulink>.
|
||||||
|
</para>
|
||||||
|
</section>
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
</chapter>
|
||||||
|
<!--
|
||||||
|
vim: expandtab tw=80 ts=4
|
||||||
|
-->
|
|
@ -0,0 +1,979 @@
|
||||||
|
/*
|
||||||
|
Generic XHTML / DocBook XHTML CSS Stylesheet.
|
||||||
|
|
||||||
|
Browser wrangling and typographic design by
|
||||||
|
Oyvind Kolas / pippin@gimp.org
|
||||||
|
|
||||||
|
Customised for Poky by
|
||||||
|
Matthew Allum / mallum@o-hand.com
|
||||||
|
|
||||||
|
Thanks to:
|
||||||
|
Liam R. E. Quin
|
||||||
|
William Skaggs
|
||||||
|
Jakub Steiner
|
||||||
|
|
||||||
|
Structure
|
||||||
|
---------
|
||||||
|
|
||||||
|
The stylesheet is divided into the following sections:
|
||||||
|
|
||||||
|
Positioning
|
||||||
|
Margins, paddings, width, font-size, clearing.
|
||||||
|
Decorations
|
||||||
|
Borders, style
|
||||||
|
Colors
|
||||||
|
Colors
|
||||||
|
Graphics
|
||||||
|
Graphical backgrounds
|
||||||
|
Nasty IE tweaks
|
||||||
|
Workarounds needed to make it work in internet explorer,
|
||||||
|
currently makes the stylesheet non validating, but up until
|
||||||
|
this point it is validating.
|
||||||
|
Mozilla extensions
|
||||||
|
Transparency for footer
|
||||||
|
Rounded corners on boxes
|
||||||
|
|
||||||
|
*/
|
||||||
|
|
||||||
|
|
||||||
|
/*************** /
|
||||||
|
/ Positioning /
|
||||||
|
/ ***************/
|
||||||
|
|
||||||
|
body {
|
||||||
|
font-family: Verdana, Sans, sans-serif;
|
||||||
|
|
||||||
|
min-width: 640px;
|
||||||
|
width: 80%;
|
||||||
|
margin: 0em auto;
|
||||||
|
padding: 2em 5em 5em 5em;
|
||||||
|
color: #333;
|
||||||
|
}
|
||||||
|
|
||||||
|
h1,h2,h3,h4,h5,h6,h7 {
|
||||||
|
font-family: Arial, Sans;
|
||||||
|
color: #00557D;
|
||||||
|
clear: both;
|
||||||
|
}
|
||||||
|
|
||||||
|
h1 {
|
||||||
|
font-size: 2em;
|
||||||
|
text-align: left;
|
||||||
|
padding: 0em 0em 0em 0em;
|
||||||
|
margin: 2em 0em 0em 0em;
|
||||||
|
}
|
||||||
|
|
||||||
|
h2.subtitle {
|
||||||
|
margin: 0.10em 0em 3.0em 0em;
|
||||||
|
padding: 0em 0em 0em 0em;
|
||||||
|
font-size: 1.8em;
|
||||||
|
padding-left: 20%;
|
||||||
|
font-weight: normal;
|
||||||
|
font-style: italic;
|
||||||
|
}
|
||||||
|
|
||||||
|
h2 {
|
||||||
|
margin: 2em 0em 0.66em 0em;
|
||||||
|
padding: 0.5em 0em 0em 0em;
|
||||||
|
font-size: 1.5em;
|
||||||
|
font-weight: bold;
|
||||||
|
}
|
||||||
|
|
||||||
|
h3.subtitle {
|
||||||
|
margin: 0em 0em 1em 0em;
|
||||||
|
padding: 0em 0em 0em 0em;
|
||||||
|
font-size: 142.14%;
|
||||||
|
text-align: right;
|
||||||
|
}
|
||||||
|
|
||||||
|
h3 {
|
||||||
|
margin: 1em 0em 0.5em 0em;
|
||||||
|
padding: 1em 0em 0em 0em;
|
||||||
|
font-size: 140%;
|
||||||
|
font-weight: bold;
|
||||||
|
}
|
||||||
|
|
||||||
|
h4 {
|
||||||
|
margin: 1em 0em 0.5em 0em;
|
||||||
|
padding: 1em 0em 0em 0em;
|
||||||
|
font-size: 120%;
|
||||||
|
font-weight: bold;
|
||||||
|
}
|
||||||
|
|
||||||
|
h5 {
|
||||||
|
margin: 1em 0em 0.5em 0em;
|
||||||
|
padding: 1em 0em 0em 0em;
|
||||||
|
font-size: 110%;
|
||||||
|
font-weight: bold;
|
||||||
|
}
|
||||||
|
|
||||||
|
h6 {
|
||||||
|
margin: 1em 0em 0em 0em;
|
||||||
|
padding: 1em 0em 0em 0em;
|
||||||
|
font-size: 110%;
|
||||||
|
font-weight: bold;
|
||||||
|
}
|
||||||
|
|
||||||
|
.authorgroup {
|
||||||
|
background-color: transparent;
|
||||||
|
background-repeat: no-repeat;
|
||||||
|
padding-top: 256px;
|
||||||
|
background-image: url("figures/kernel-title.png");
|
||||||
|
background-position: left top;
|
||||||
|
margin-top: -256px;
|
||||||
|
padding-right: 50px;
|
||||||
|
margin-left: 0px;
|
||||||
|
text-align: right;
|
||||||
|
width: 740px;
|
||||||
|
}
|
||||||
|
|
||||||
|
h3.author {
|
||||||
|
margin: 0em 0me 0em 0em;
|
||||||
|
padding: 0em 0em 0em 0em;
|
||||||
|
font-weight: normal;
|
||||||
|
font-size: 100%;
|
||||||
|
color: #333;
|
||||||
|
clear: both;
|
||||||
|
}
|
||||||
|
|
||||||
|
.author tt.email {
|
||||||
|
font-size: 66%;
|
||||||
|
}
|
||||||
|
|
||||||
|
.titlepage hr {
|
||||||
|
width: 0em;
|
||||||
|
clear: both;
|
||||||
|
}
|
||||||
|
|
||||||
|
.revhistory {
|
||||||
|
padding-top: 2em;
|
||||||
|
clear: both;
|
||||||
|
}
|
||||||
|
|
||||||
|
.toc,
|
||||||
|
.list-of-tables,
|
||||||
|
.list-of-examples,
|
||||||
|
.list-of-figures {
|
||||||
|
padding: 1.33em 0em 2.5em 0em;
|
||||||
|
color: #00557D;
|
||||||
|
}
|
||||||
|
|
||||||
|
.toc p,
|
||||||
|
.list-of-tables p,
|
||||||
|
.list-of-figures p,
|
||||||
|
.list-of-examples p {
|
||||||
|
padding: 0em 0em 0em 0em;
|
||||||
|
padding: 0em 0em 0.3em;
|
||||||
|
margin: 1.5em 0em 0em 0em;
|
||||||
|
}
|
||||||
|
|
||||||
|
.toc p b,
|
||||||
|
.list-of-tables p b,
|
||||||
|
.list-of-figures p b,
|
||||||
|
.list-of-examples p b{
|
||||||
|
font-size: 100.0%;
|
||||||
|
font-weight: bold;
|
||||||
|
}
|
||||||
|
|
||||||
|
.toc dl,
|
||||||
|
.list-of-tables dl,
|
||||||
|
.list-of-figures dl,
|
||||||
|
.list-of-examples dl {
|
||||||
|
margin: 0em 0em 0.5em 0em;
|
||||||
|
padding: 0em 0em 0em 0em;
|
||||||
|
}
|
||||||
|
|
||||||
|
.toc dt {
|
||||||
|
margin: 0em 0em 0em 0em;
|
||||||
|
padding: 0em 0em 0em 0em;
|
||||||
|
}
|
||||||
|
|
||||||
|
.toc dd {
|
||||||
|
margin: 0em 0em 0em 2.6em;
|
||||||
|
padding: 0em 0em 0em 0em;
|
||||||
|
}
|
||||||
|
|
||||||
|
div.glossary dl,
|
||||||
|
div.variablelist dl {
|
||||||
|
}
|
||||||
|
|
||||||
|
.glossary dl dt,
|
||||||
|
.variablelist dl dt,
|
||||||
|
.variablelist dl dt span.term {
|
||||||
|
font-weight: normal;
|
||||||
|
width: 20em;
|
||||||
|
text-align: right;
|
||||||
|
}
|
||||||
|
|
||||||
|
.variablelist dl dt {
|
||||||
|
margin-top: 0.5em;
|
||||||
|
}
|
||||||
|
|
||||||
|
.glossary dl dd,
|
||||||
|
.variablelist dl dd {
|
||||||
|
margin-top: -1em;
|
||||||
|
margin-left: 25.5em;
|
||||||
|
}
|
||||||
|
|
||||||
|
.glossary dd p,
|
||||||
|
.variablelist dd p {
|
||||||
|
margin-top: 0em;
|
||||||
|
margin-bottom: 1em;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
div.calloutlist table td {
|
||||||
|
padding: 0em 0em 0em 0em;
|
||||||
|
margin: 0em 0em 0em 0em;
|
||||||
|
}
|
||||||
|
|
||||||
|
div.calloutlist table td p {
|
||||||
|
margin-top: 0em;
|
||||||
|
margin-bottom: 1em;
|
||||||
|
}
|
||||||
|
|
||||||
|
div p.copyright {
|
||||||
|
text-align: left;
|
||||||
|
}
|
||||||
|
|
||||||
|
div.legalnotice p.legalnotice-title {
|
||||||
|
margin-bottom: 0em;
|
||||||
|
}
|
||||||
|
|
||||||
|
p {
|
||||||
|
line-height: 1.5em;
|
||||||
|
margin-top: 0em;
|
||||||
|
|
||||||
|
}
|
||||||
|
|
||||||
|
dl {
|
||||||
|
padding-top: 0em;
|
||||||
|
}
|
||||||
|
|
||||||
|
hr {
|
||||||
|
border: solid 1px;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
.mediaobject,
|
||||||
|
.mediaobjectco {
|
||||||
|
text-align: center;
|
||||||
|
}
|
||||||
|
|
||||||
|
img {
|
||||||
|
border: none;
|
||||||
|
}
|
||||||
|
|
||||||
|
ul {
|
||||||
|
padding: 0em 0em 0em 1.5em;
|
||||||
|
}
|
||||||
|
|
||||||
|
ul li {
|
||||||
|
padding: 0em 0em 0em 0em;
|
||||||
|
}
|
||||||
|
|
||||||
|
ul li p {
|
||||||
|
text-align: left;
|
||||||
|
}
|
||||||
|
|
||||||
|
table {
|
||||||
|
width :100%;
|
||||||
|
}
|
||||||
|
|
||||||
|
th {
|
||||||
|
padding: 0.25em;
|
||||||
|
text-align: left;
|
||||||
|
font-weight: normal;
|
||||||
|
vertical-align: top;
|
||||||
|
}
|
||||||
|
|
||||||
|
td {
|
||||||
|
padding: 0.25em;
|
||||||
|
vertical-align: top;
|
||||||
|
}
|
||||||
|
|
||||||
|
p a[id] {
|
||||||
|
margin: 0px;
|
||||||
|
padding: 0px;
|
||||||
|
display: inline;
|
||||||
|
background-image: none;
|
||||||
|
}
|
||||||
|
|
||||||
|
a {
|
||||||
|
text-decoration: underline;
|
||||||
|
color: #444;
|
||||||
|
}
|
||||||
|
|
||||||
|
pre {
|
||||||
|
overflow: auto;
|
||||||
|
}
|
||||||
|
|
||||||
|
a:hover {
|
||||||
|
text-decoration: underline;
|
||||||
|
/*font-weight: bold;*/
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
div.informalfigure,
|
||||||
|
div.informalexample,
|
||||||
|
div.informaltable,
|
||||||
|
div.figure,
|
||||||
|
div.table,
|
||||||
|
div.example {
|
||||||
|
margin: 1em 0em;
|
||||||
|
padding: 1em;
|
||||||
|
page-break-inside: avoid;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
div.informalfigure p.title b,
|
||||||
|
div.informalexample p.title b,
|
||||||
|
div.informaltable p.title b,
|
||||||
|
div.figure p.title b,
|
||||||
|
div.example p.title b,
|
||||||
|
div.table p.title b{
|
||||||
|
padding-top: 0em;
|
||||||
|
margin-top: 0em;
|
||||||
|
font-size: 100%;
|
||||||
|
font-weight: normal;
|
||||||
|
}
|
||||||
|
|
||||||
|
.mediaobject .caption,
|
||||||
|
.mediaobject .caption p {
|
||||||
|
text-align: center;
|
||||||
|
font-size: 80%;
|
||||||
|
padding-top: 0.5em;
|
||||||
|
padding-bottom: 0.5em;
|
||||||
|
}
|
||||||
|
|
||||||
|
.epigraph {
|
||||||
|
padding-left: 55%;
|
||||||
|
margin-bottom: 1em;
|
||||||
|
}
|
||||||
|
|
||||||
|
.epigraph p {
|
||||||
|
text-align: left;
|
||||||
|
}
|
||||||
|
|
||||||
|
.epigraph .quote {
|
||||||
|
font-style: italic;
|
||||||
|
}
|
||||||
|
.epigraph .attribution {
|
||||||
|
font-style: normal;
|
||||||
|
text-align: right;
|
||||||
|
}
|
||||||
|
|
||||||
|
span.application {
|
||||||
|
font-style: italic;
|
||||||
|
}
|
||||||
|
|
||||||
|
.programlisting {
|
||||||
|
font-family: monospace;
|
||||||
|
font-size: 80%;
|
||||||
|
white-space: pre;
|
||||||
|
margin: 1.33em 0em;
|
||||||
|
padding: 1.33em;
|
||||||
|
}
|
||||||
|
|
||||||
|
.tip,
|
||||||
|
.warning,
|
||||||
|
.caution,
|
||||||
|
.note {
|
||||||
|
margin-top: 1em;
|
||||||
|
margin-bottom: 1em;
|
||||||
|
|
||||||
|
}
|
||||||
|
|
||||||
|
/* force full width of table within div */
|
||||||
|
.tip table,
|
||||||
|
.warning table,
|
||||||
|
.caution table,
|
||||||
|
.note table {
|
||||||
|
border: none;
|
||||||
|
width: 100%;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
.tip table th,
|
||||||
|
.warning table th,
|
||||||
|
.caution table th,
|
||||||
|
.note table th {
|
||||||
|
padding: 0.8em 0.0em 0.0em 0.0em;
|
||||||
|
margin : 0em 0em 0em 0em;
|
||||||
|
}
|
||||||
|
|
||||||
|
.tip p,
|
||||||
|
.warning p,
|
||||||
|
.caution p,
|
||||||
|
.note p {
|
||||||
|
margin-top: 0.5em;
|
||||||
|
margin-bottom: 0.5em;
|
||||||
|
padding-right: 1em;
|
||||||
|
text-align: left;
|
||||||
|
}
|
||||||
|
|
||||||
|
.acronym {
|
||||||
|
text-transform: uppercase;
|
||||||
|
}
|
||||||
|
|
||||||
|
b.keycap,
|
||||||
|
.keycap {
|
||||||
|
padding: 0.09em 0.3em;
|
||||||
|
margin: 0em;
|
||||||
|
}
|
||||||
|
|
||||||
|
.itemizedlist li {
|
||||||
|
clear: none;
|
||||||
|
}
|
||||||
|
|
||||||
|
.filename {
|
||||||
|
font-size: medium;
|
||||||
|
font-family: Courier, monospace;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
div.navheader, div.heading{
|
||||||
|
position: absolute;
|
||||||
|
left: 0em;
|
||||||
|
top: 0em;
|
||||||
|
width: 100%;
|
||||||
|
background-color: #cdf;
|
||||||
|
width: 100%;
|
||||||
|
}
|
||||||
|
|
||||||
|
div.navfooter, div.footing{
|
||||||
|
position: fixed;
|
||||||
|
left: 0em;
|
||||||
|
bottom: 0em;
|
||||||
|
background-color: #eee;
|
||||||
|
width: 100%;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
div.navheader td,
|
||||||
|
div.navfooter td {
|
||||||
|
font-size: 66%;
|
||||||
|
}
|
||||||
|
|
||||||
|
div.navheader table th {
|
||||||
|
/*font-family: Georgia, Times, serif;*/
|
||||||
|
/*font-size: x-large;*/
|
||||||
|
font-size: 80%;
|
||||||
|
}
|
||||||
|
|
||||||
|
div.navheader table {
|
||||||
|
border-left: 0em;
|
||||||
|
border-right: 0em;
|
||||||
|
border-top: 0em;
|
||||||
|
width: 100%;
|
||||||
|
}
|
||||||
|
|
||||||
|
div.navfooter table {
|
||||||
|
border-left: 0em;
|
||||||
|
border-right: 0em;
|
||||||
|
border-bottom: 0em;
|
||||||
|
width: 100%;
|
||||||
|
}
|
||||||
|
|
||||||
|
div.navheader table td a,
|
||||||
|
div.navfooter table td a {
|
||||||
|
color: #777;
|
||||||
|
text-decoration: none;
|
||||||
|
}
|
||||||
|
|
||||||
|
/* normal text in the footer */
|
||||||
|
div.navfooter table td {
|
||||||
|
color: black;
|
||||||
|
}
|
||||||
|
|
||||||
|
div.navheader table td a:visited,
|
||||||
|
div.navfooter table td a:visited {
|
||||||
|
color: #444;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
/* links in header and footer */
|
||||||
|
div.navheader table td a:hover,
|
||||||
|
div.navfooter table td a:hover {
|
||||||
|
text-decoration: underline;
|
||||||
|
background-color: transparent;
|
||||||
|
color: #33a;
|
||||||
|
}
|
||||||
|
|
||||||
|
div.navheader hr,
|
||||||
|
div.navfooter hr {
|
||||||
|
display: none;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
.qandaset tr.question td p {
|
||||||
|
margin: 0em 0em 1em 0em;
|
||||||
|
padding: 0em 0em 0em 0em;
|
||||||
|
}
|
||||||
|
|
||||||
|
.qandaset tr.answer td p {
|
||||||
|
margin: 0em 0em 1em 0em;
|
||||||
|
padding: 0em 0em 0em 0em;
|
||||||
|
}
|
||||||
|
.answer td {
|
||||||
|
padding-bottom: 1.5em;
|
||||||
|
}
|
||||||
|
|
||||||
|
.emphasis {
|
||||||
|
font-weight: bold;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
/************* /
|
||||||
|
/ decorations /
|
||||||
|
/ *************/
|
||||||
|
|
||||||
|
.titlepage {
|
||||||
|
}
|
||||||
|
|
||||||
|
.part .title {
|
||||||
|
}
|
||||||
|
|
||||||
|
.subtitle {
|
||||||
|
border: none;
|
||||||
|
}
|
||||||
|
|
||||||
|
/*
|
||||||
|
h1 {
|
||||||
|
border: none;
|
||||||
|
}
|
||||||
|
|
||||||
|
h2 {
|
||||||
|
border-top: solid 0.2em;
|
||||||
|
border-bottom: solid 0.06em;
|
||||||
|
}
|
||||||
|
|
||||||
|
h3 {
|
||||||
|
border-top: 0em;
|
||||||
|
border-bottom: solid 0.06em;
|
||||||
|
}
|
||||||
|
|
||||||
|
h4 {
|
||||||
|
border: 0em;
|
||||||
|
border-bottom: solid 0.06em;
|
||||||
|
}
|
||||||
|
|
||||||
|
h5 {
|
||||||
|
border: 0em;
|
||||||
|
}
|
||||||
|
*/
|
||||||
|
|
||||||
|
.programlisting {
|
||||||
|
border: solid 1px;
|
||||||
|
}
|
||||||
|
|
||||||
|
div.figure,
|
||||||
|
div.table,
|
||||||
|
div.informalfigure,
|
||||||
|
div.informaltable,
|
||||||
|
div.informalexample,
|
||||||
|
div.example {
|
||||||
|
border: 1px solid;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
.tip,
|
||||||
|
.warning,
|
||||||
|
.caution,
|
||||||
|
.note {
|
||||||
|
border: 1px solid;
|
||||||
|
}
|
||||||
|
|
||||||
|
.tip table th,
|
||||||
|
.warning table th,
|
||||||
|
.caution table th,
|
||||||
|
.note table th {
|
||||||
|
border-bottom: 1px solid;
|
||||||
|
}
|
||||||
|
|
||||||
|
.question td {
|
||||||
|
border-top: 1px solid black;
|
||||||
|
}
|
||||||
|
|
||||||
|
.answer {
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
b.keycap,
|
||||||
|
.keycap {
|
||||||
|
border: 1px solid;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
div.navheader, div.heading{
|
||||||
|
border-bottom: 1px solid;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
div.navfooter, div.footing{
|
||||||
|
border-top: 1px solid;
|
||||||
|
}
|
||||||
|
|
||||||
|
/********* /
|
||||||
|
/ colors /
|
||||||
|
/ *********/
|
||||||
|
|
||||||
|
body {
|
||||||
|
color: #333;
|
||||||
|
background: white;
|
||||||
|
}
|
||||||
|
|
||||||
|
a {
|
||||||
|
background: transparent;
|
||||||
|
}
|
||||||
|
|
||||||
|
a:hover {
|
||||||
|
background-color: #dedede;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
h1,
|
||||||
|
h2,
|
||||||
|
h3,
|
||||||
|
h4,
|
||||||
|
h5,
|
||||||
|
h6,
|
||||||
|
h7,
|
||||||
|
h8 {
|
||||||
|
background-color: transparent;
|
||||||
|
}
|
||||||
|
|
||||||
|
hr {
|
||||||
|
border-color: #aaa;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
.tip, .warning, .caution, .note {
|
||||||
|
border-color: #fff;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
.tip table th,
|
||||||
|
.warning table th,
|
||||||
|
.caution table th,
|
||||||
|
.note table th {
|
||||||
|
border-bottom-color: #fff;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
.warning {
|
||||||
|
background-color: #f0f0f2;
|
||||||
|
}
|
||||||
|
|
||||||
|
.caution {
|
||||||
|
background-color: #f0f0f2;
|
||||||
|
}
|
||||||
|
|
||||||
|
.tip {
|
||||||
|
background-color: #f0f0f2;
|
||||||
|
}
|
||||||
|
|
||||||
|
.note {
|
||||||
|
background-color: #f0f0f2;
|
||||||
|
}
|
||||||
|
|
||||||
|
.glossary dl dt,
|
||||||
|
.variablelist dl dt,
|
||||||
|
.variablelist dl dt span.term {
|
||||||
|
color: #044;
|
||||||
|
}
|
||||||
|
|
||||||
|
div.figure,
|
||||||
|
div.table,
|
||||||
|
div.example,
|
||||||
|
div.informalfigure,
|
||||||
|
div.informaltable,
|
||||||
|
div.informalexample {
|
||||||
|
border-color: #aaa;
|
||||||
|
}
|
||||||
|
|
||||||
|
pre.programlisting {
|
||||||
|
color: black;
|
||||||
|
background-color: #fff;
|
||||||
|
border-color: #aaa;
|
||||||
|
border-width: 2px;
|
||||||
|
}
|
||||||
|
|
||||||
|
.guimenu,
|
||||||
|
.guilabel,
|
||||||
|
.guimenuitem {
|
||||||
|
background-color: #eee;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
b.keycap,
|
||||||
|
.keycap {
|
||||||
|
background-color: #eee;
|
||||||
|
border-color: #999;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
div.navheader {
|
||||||
|
border-color: black;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
div.navfooter {
|
||||||
|
border-color: black;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
/*********** /
|
||||||
|
/ graphics /
|
||||||
|
/ ***********/
|
||||||
|
|
||||||
|
/*
|
||||||
|
body {
|
||||||
|
background-image: url("images/body_bg.jpg");
|
||||||
|
background-attachment: fixed;
|
||||||
|
}
|
||||||
|
|
||||||
|
.navheader,
|
||||||
|
.note,
|
||||||
|
.tip {
|
||||||
|
background-image: url("images/note_bg.jpg");
|
||||||
|
background-attachment: fixed;
|
||||||
|
}
|
||||||
|
|
||||||
|
.warning,
|
||||||
|
.caution {
|
||||||
|
background-image: url("images/warning_bg.jpg");
|
||||||
|
background-attachment: fixed;
|
||||||
|
}
|
||||||
|
|
||||||
|
.figure,
|
||||||
|
.informalfigure,
|
||||||
|
.example,
|
||||||
|
.informalexample,
|
||||||
|
.table,
|
||||||
|
.informaltable {
|
||||||
|
background-image: url("images/figure_bg.jpg");
|
||||||
|
background-attachment: fixed;
|
||||||
|
}
|
||||||
|
|
||||||
|
*/
|
||||||
|
h1,
|
||||||
|
h2,
|
||||||
|
h3,
|
||||||
|
h4,
|
||||||
|
h5,
|
||||||
|
h6,
|
||||||
|
h7{
|
||||||
|
}
|
||||||
|
|
||||||
|
/*
|
||||||
|
Example of how to stick an image as part of the title.
|
||||||
|
|
||||||
|
div.article .titlepage .title
|
||||||
|
{
|
||||||
|
background-image: url("figures/white-on-black.png");
|
||||||
|
background-position: center;
|
||||||
|
background-repeat: repeat-x;
|
||||||
|
}
|
||||||
|
*/
|
||||||
|
|
||||||
|
div.preface .titlepage .title,
|
||||||
|
div.colophon .title,
|
||||||
|
div.chapter .titlepage .title,
|
||||||
|
div.article .titlepage .title
|
||||||
|
{
|
||||||
|
}
|
||||||
|
|
||||||
|
div.section div.section .titlepage .title,
|
||||||
|
div.sect2 .titlepage .title {
|
||||||
|
background: none;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
h1.title {
|
||||||
|
background-color: transparent;
|
||||||
|
background-image: url("figures/yocto-project-bw.png");
|
||||||
|
background-repeat: no-repeat;
|
||||||
|
height: 256px;
|
||||||
|
text-indent: -9000px;
|
||||||
|
overflow:hidden;
|
||||||
|
}
|
||||||
|
|
||||||
|
h2.subtitle {
|
||||||
|
background-color: transparent;
|
||||||
|
text-indent: -9000px;
|
||||||
|
overflow:hidden;
|
||||||
|
width: 0px;
|
||||||
|
display: none;
|
||||||
|
}
|
||||||
|
|
||||||
|
/*************************************** /
|
||||||
|
/ pippin.gimp.org specific alterations /
|
||||||
|
/ ***************************************/
|
||||||
|
|
||||||
|
/*
|
||||||
|
div.heading, div.navheader {
|
||||||
|
color: #777;
|
||||||
|
font-size: 80%;
|
||||||
|
padding: 0;
|
||||||
|
margin: 0;
|
||||||
|
text-align: left;
|
||||||
|
position: absolute;
|
||||||
|
top: 0px;
|
||||||
|
left: 0px;
|
||||||
|
width: 100%;
|
||||||
|
height: 50px;
|
||||||
|
background: url('/gfx/heading_bg.png') transparent;
|
||||||
|
background-repeat: repeat-x;
|
||||||
|
background-attachment: fixed;
|
||||||
|
border: none;
|
||||||
|
}
|
||||||
|
|
||||||
|
div.heading a {
|
||||||
|
color: #444;
|
||||||
|
}
|
||||||
|
|
||||||
|
div.footing, div.navfooter {
|
||||||
|
border: none;
|
||||||
|
color: #ddd;
|
||||||
|
font-size: 80%;
|
||||||
|
text-align:right;
|
||||||
|
|
||||||
|
width: 100%;
|
||||||
|
padding-top: 10px;
|
||||||
|
position: absolute;
|
||||||
|
bottom: 0px;
|
||||||
|
left: 0px;
|
||||||
|
|
||||||
|
background: url('/gfx/footing_bg.png') transparent;
|
||||||
|
}
|
||||||
|
*/
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
/****************** /
|
||||||
|
/ nasty ie tweaks /
|
||||||
|
/ ******************/
|
||||||
|
|
||||||
|
/*
|
||||||
|
div.heading, div.navheader {
|
||||||
|
width:expression(document.body.clientWidth + "px");
|
||||||
|
}
|
||||||
|
|
||||||
|
div.footing, div.navfooter {
|
||||||
|
width:expression(document.body.clientWidth + "px");
|
||||||
|
margin-left:expression("-5em");
|
||||||
|
}
|
||||||
|
body {
|
||||||
|
padding:expression("4em 5em 0em 5em");
|
||||||
|
}
|
||||||
|
*/
|
||||||
|
|
||||||
|
/**************************************** /
|
||||||
|
/ mozilla vendor specific css extensions /
|
||||||
|
/ ****************************************/
|
||||||
|
/*
|
||||||
|
div.navfooter, div.footing{
|
||||||
|
-moz-opacity: 0.8em;
|
||||||
|
}
|
||||||
|
|
||||||
|
div.figure,
|
||||||
|
div.table,
|
||||||
|
div.informalfigure,
|
||||||
|
div.informaltable,
|
||||||
|
div.informalexample,
|
||||||
|
div.example,
|
||||||
|
.tip,
|
||||||
|
.warning,
|
||||||
|
.caution,
|
||||||
|
.note {
|
||||||
|
-moz-border-radius: 0.5em;
|
||||||
|
}
|
||||||
|
|
||||||
|
b.keycap,
|
||||||
|
.keycap {
|
||||||
|
-moz-border-radius: 0.3em;
|
||||||
|
}
|
||||||
|
*/
|
||||||
|
|
||||||
|
table tr td table tr td {
|
||||||
|
display: none;
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
hr {
|
||||||
|
display: none;
|
||||||
|
}
|
||||||
|
|
||||||
|
table {
|
||||||
|
border: 0em;
|
||||||
|
}
|
||||||
|
|
||||||
|
.photo {
|
||||||
|
float: right;
|
||||||
|
margin-left: 1.5em;
|
||||||
|
margin-bottom: 1.5em;
|
||||||
|
margin-top: 0em;
|
||||||
|
max-width: 17em;
|
||||||
|
border: 1px solid gray;
|
||||||
|
padding: 3px;
|
||||||
|
background: white;
|
||||||
|
}
|
||||||
|
.seperator {
|
||||||
|
padding-top: 2em;
|
||||||
|
clear: both;
|
||||||
|
}
|
||||||
|
|
||||||
|
#validators {
|
||||||
|
margin-top: 5em;
|
||||||
|
text-align: right;
|
||||||
|
color: #777;
|
||||||
|
}
|
||||||
|
@media print {
|
||||||
|
body {
|
||||||
|
font-size: 8pt;
|
||||||
|
}
|
||||||
|
.noprint {
|
||||||
|
display: none;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
.tip,
|
||||||
|
.note {
|
||||||
|
background: #f0f0f2;
|
||||||
|
color: #333;
|
||||||
|
padding: 20px;
|
||||||
|
margin: 20px;
|
||||||
|
}
|
||||||
|
|
||||||
|
.tip h3,
|
||||||
|
.note h3 {
|
||||||
|
padding: 0em;
|
||||||
|
margin: 0em;
|
||||||
|
font-size: 2em;
|
||||||
|
font-weight: bold;
|
||||||
|
color: #333;
|
||||||
|
}
|
||||||
|
|
||||||
|
.tip a,
|
||||||
|
.note a {
|
||||||
|
color: #333;
|
||||||
|
text-decoration: underline;
|
||||||
|
}
|
||||||
|
|
||||||
|
.footnote {
|
||||||
|
font-size: small;
|
||||||
|
color: #333;
|
||||||
|
}
|
||||||
|
|
||||||
|
/* Changes the announcement text */
|
||||||
|
.tip h3,
|
||||||
|
.warning h3,
|
||||||
|
.caution h3,
|
||||||
|
.note h3 {
|
||||||
|
font-size:large;
|
||||||
|
color: #00557D;
|
||||||
|
}
|
||||||
|
|
|
@ -0,0 +1,104 @@
|
||||||
|
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
|
||||||
|
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
|
||||||
|
[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
|
||||||
|
|
||||||
|
<book id='kernel-manual' lang='en'
|
||||||
|
xmlns:xi="http://www.w3.org/2003/XInclude"
|
||||||
|
xmlns="http://docbook.org/ns/docbook"
|
||||||
|
>
|
||||||
|
<bookinfo>
|
||||||
|
|
||||||
|
<mediaobject>
|
||||||
|
<imageobject>
|
||||||
|
<imagedata fileref='figures/kernel-title.png'
|
||||||
|
format='SVG'
|
||||||
|
align='left' scalefit='1' width='100%'/>
|
||||||
|
</imageobject>
|
||||||
|
</mediaobject>
|
||||||
|
|
||||||
|
<title></title>
|
||||||
|
|
||||||
|
<authorgroup>
|
||||||
|
<author>
|
||||||
|
<firstname>Bruce</firstname> <surname>Ashfield</surname>
|
||||||
|
<affiliation>
|
||||||
|
<orgname>Wind River Corporation</orgname>
|
||||||
|
</affiliation>
|
||||||
|
<email>bruce.ashfield@windriver.com</email>
|
||||||
|
</author>
|
||||||
|
</authorgroup>
|
||||||
|
|
||||||
|
<revhistory>
|
||||||
|
<revision>
|
||||||
|
<revnumber>0.9</revnumber>
|
||||||
|
<date>24 November 2010</date>
|
||||||
|
<revremark>The initial document draft released with the Yocto Project 0.9 Release.</revremark>
|
||||||
|
</revision>
|
||||||
|
<revision>
|
||||||
|
<revnumber>1.0</revnumber>
|
||||||
|
<date>6 April 2011</date>
|
||||||
|
<revremark>Released with the Yocto Project 1.0 Release.</revremark>
|
||||||
|
</revision>
|
||||||
|
<revision>
|
||||||
|
<revnumber>1.0.1</revnumber>
|
||||||
|
<date>23 May 2011</date>
|
||||||
|
<revremark>Released with the Yocto Project 1.0.1 Release.</revremark>
|
||||||
|
</revision>
|
||||||
|
<revision>
|
||||||
|
<revnumber>1.1</revnumber>
|
||||||
|
<date>6 October 2011</date>
|
||||||
|
<revremark>Released with the Yocto Project 1.1 Release.</revremark>
|
||||||
|
</revision>
|
||||||
|
<revision>
|
||||||
|
<revnumber>1.2</revnumber>
|
||||||
|
<date>April 2012</date>
|
||||||
|
<revremark>Released with the Yocto Project 1.2 Release.</revremark>
|
||||||
|
</revision>
|
||||||
|
<revision>
|
||||||
|
<revnumber>1.3</revnumber>
|
||||||
|
<date>October 2012</date>
|
||||||
|
<revremark>Released with the Yocto Project 1.3 Release.</revremark>
|
||||||
|
</revision>
|
||||||
|
<revision>
|
||||||
|
<revnumber>1.4</revnumber>
|
||||||
|
<date>Sometime in 2013</date>
|
||||||
|
<revremark>Released with the Yocto Project 1.4 Release.</revremark>
|
||||||
|
</revision>
|
||||||
|
</revhistory>
|
||||||
|
|
||||||
|
<copyright>
|
||||||
|
<year>©RIGHT_YEAR;</year>
|
||||||
|
<holder>Linux Foundation</holder>
|
||||||
|
</copyright>
|
||||||
|
|
||||||
|
<legalnotice>
|
||||||
|
<para>
|
||||||
|
Permission is granted to copy, distribute and/or modify this document under
|
||||||
|
the terms of the <ulink type="http" url="http://creativecommons.org/licenses/by-sa/2.0/uk/">Creative Commons Attribution-Share Alike 2.0 UK: England & Wales</ulink> as published by Creative Commons.
|
||||||
|
</para>
|
||||||
|
<note>
|
||||||
|
Due to production processes, there could be differences between the Yocto Project
|
||||||
|
documentation bundled in the release tarball and the
|
||||||
|
<ulink url='&YOCTO_DOCS_KERNEL_URL;'>Yocto Project Kernel Architecture and Use Manual</ulink> on
|
||||||
|
the <ulink url='&YOCTO_HOME_URL;'>Yocto Project</ulink> website.
|
||||||
|
For the latest version of this manual, see the manual on the website.
|
||||||
|
</note>
|
||||||
|
</legalnotice>
|
||||||
|
|
||||||
|
</bookinfo>
|
||||||
|
|
||||||
|
<xi:include href="kernel-doc-intro.xml"/>
|
||||||
|
|
||||||
|
<xi:include href="kernel-concepts.xml"/>
|
||||||
|
|
||||||
|
<xi:include href="kernel-how-to.xml"/>
|
||||||
|
|
||||||
|
<!-- <index id='index'>
|
||||||
|
<title>Index</title>
|
||||||
|
</index>
|
||||||
|
-->
|
||||||
|
|
||||||
|
</book>
|
||||||
|
<!--
|
||||||
|
vim: expandtab tw=80 ts=4
|
||||||
|
-->
|
Loading…
Reference in New Issue