documentation/poky-ref-manual/extendpoky.xml: intro changed and order changed
Beefed up the introductory paragraph and I re-ordered the "Making and Maintaining Changes" section towards the end of the chapter. (From yocto-docs rev: a58c0e73d720ffb7a4931fbc196ea3831992b514) Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark
Richard Purdie
parent
caab52f6cc
commit
d2f1ca8cba
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@ -3,13 +3,14 @@
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<chapter id='extendpoky'>
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<title>Extending the Yocto Project</title>
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<title>Common Tasks</title>
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<para>
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This chapter provides information about how to extend the functionality
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already present in the Yocto Project.
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The chapter also documents standard tasks such as adding new
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This chapter describes standard tasks such as adding new
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software packages, extending or customizing images or porting the Yocto Project to
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new hardware (adding a new machine).
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The chapter also describes ways to modify package source code, combine multiple
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versions of library files into a single image, track license changes, and handle
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a package name alias.
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Finally, the chapter contains advice about how to make changes to the
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Yocto Project to achieve the best results.
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</para>
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@ -658,324 +659,6 @@
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</section>
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</section>
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<section id="usingpoky-changes">
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<title>Making and Maintaining Changes</title>
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<para>
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Because the Yocto Project is extremely configurable and flexible,
|
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we recognize that developers will want
|
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to extend, configure or optimize it for their specific uses.
|
||||
To best keep pace with future Yocto Project changes,
|
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we recommend you make controlled changes to the Yocto Project.
|
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</para>
|
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|
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<para>
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The Yocto Project supports a <link linkend='usingpoky-changes-layers'>"layers"</link> concept.
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If you use layers properly, you can ease future upgrades and allow segregation
|
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between the Yocto Project core and a given developer's changes.
|
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The following section provides more advice on managing changes to the Yocto Project.
|
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</para>
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|
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<section id="usingpoky-changes-layers">
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<title>BitBake Layers</title>
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<para>
|
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Often, developers want to extend the Yocto Project either by adding packages
|
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or by overriding files contained within the Yocto Project to add their own
|
||||
functionality.
|
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BitBake has a powerful mechanism called
|
||||
"layers", which provides a way to handle this extension in a fully
|
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supported and non-invasive fashion.
|
||||
</para>
|
||||
|
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<para>
|
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The Yocto Project files include several additional layers such as
|
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<filename>meta-rt</filename> and <filename>meta-yocto</filename>
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that demonstrate this functionality.
|
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The <filename>meta-rt</filename> layer is not enabled by default.
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However, the <filename>meta-yocto</filename> layer is.
|
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</para>
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|
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<para>
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To enable a layer, you simply add the layer's path to the
|
||||
<filename><link linkend='var-BBLAYERS'>BBLAYERS</link></filename> variable in your
|
||||
<filename>bblayers.conf</filename> file, which is found in the Yocto Project file's
|
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build directory.
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The following example shows how to enable the <filename>meta-rt</filename>:
|
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<literallayout class='monospaced'>
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LCONF_VERSION = "1"
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|
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BBFILES ?= ""
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BBLAYERS = " \
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/path/to/poky/meta \
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/path/to/poky/meta-yocto \
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/path/to/poky/meta-rt \
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"
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</literallayout>
|
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</para>
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|
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<para>
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BitBake parses each <filename>conf/layer.conf</filename> file for each layer in
|
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<filename>BBLAYERS</filename>
|
||||
and adds the recipes, classes and configurations contained within the layer to
|
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the Yocto Project.
|
||||
To create your own layer, independent of the Yocto Project files,
|
||||
simply create a directory with a <filename>conf/layer.conf</filename> file and
|
||||
add the directory to your <filename>bblayers.conf</filename> file.
|
||||
</para>
|
||||
|
||||
<para>
|
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The <filename>meta-yocto/conf/layer.conf</filename> file demonstrates the
|
||||
required syntax:
|
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<literallayout class='monospaced'>
|
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# We have a conf and classes directory, add to BBPATH
|
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BBPATH := "${BBPATH}:${LAYERDIR}"
|
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|
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# We have a packages directory, add to BBFILES
|
||||
BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb \
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${LAYERDIR}/recipes-*/*/*.bbappend"
|
||||
|
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BBFILE_COLLECTIONS += "yocto"
|
||||
BBFILE_PATTERN_yocto := "^${LAYERDIR}/"
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||||
BBFILE_PRIORITY_yocto = "5"
|
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</literallayout>
|
||||
</para>
|
||||
|
||||
<para>
|
||||
In the previous example, the recipes for the layers are added to
|
||||
<filename><link linkend='var-BBFILES'>BBFILES</link></filename>.
|
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The <filename><link linkend='var-BBFILE_COLLECTIONS'>BBFILE_COLLECTIONS</link></filename>
|
||||
variable is then appended with the layer name.
|
||||
The <filename><link linkend='var-BBFILE_PATTERN'>BBFILE_PATTERN</link></filename> variable
|
||||
immediately expands with a regular expression used to match files from
|
||||
<filename>BBFILES</filename> into
|
||||
a particular layer, in this case by using the base pathname.
|
||||
The <filename><link linkend='var-BBFILE_PRIORITY'>BBFILE_PRIORITY</link></filename> variable
|
||||
then assigns different priorities to the files in different layers.
|
||||
Applying priorities is useful in situations where the same package might appear in multiple
|
||||
layers and allows you to choose what layer should take precedence.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Note the use of the <filename><link linkend='var-LAYERDIR'>LAYERDIR</link></filename>
|
||||
variable with the immediate expansion operator.
|
||||
The <filename>LAYERDIR</filename> variable expands to the directory of the current layer and
|
||||
requires the immediate expansion operator so that BitBake does not wait to expand the variable
|
||||
when it's parsing a different directory.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
BitBake can locate where other <filename>.bbclass</filename> and configuration files
|
||||
are applied through the <filename>BBPATH</filename> environment variable.
|
||||
For these cases, BitBake uses the first file with the matching name found in
|
||||
<filename>BBPATH</filename>.
|
||||
This is similar to the way the <filename>PATH</filename> variable is used for binaries.
|
||||
We recommend, therefore, that you use unique <filename>.bbclass</filename>
|
||||
and configuration file names in your custom layer.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
We also recommend the following:
|
||||
<itemizedlist>
|
||||
<listitem><para>Store custom layers in a Git repository that uses the
|
||||
<filename>meta-prvt-XXXX</filename> format.</para></listitem>
|
||||
<listitem><para>Clone the repository alongside other <filename>meta</filename>
|
||||
directories in the Yocto Project source files area.</para></listitem>
|
||||
</itemizedlist>
|
||||
Following these recommendations keeps your Yocto Project files area and
|
||||
its configuration entirely inside the Yocto Project's core base.
|
||||
</para>
|
||||
</section>
|
||||
|
||||
<section id="usingpoky-changes-commits">
|
||||
<title>Committing Changes</title>
|
||||
|
||||
<para>
|
||||
Modifications to the Yocto Project are often managed under some kind of source
|
||||
revision control system.
|
||||
Because some simple practices can significantly improve usability, policy for committing changes
|
||||
is important.
|
||||
It helps to use a consistent documentation style when committing changes.
|
||||
The Yocto Project development team has found the following practices work well:
|
||||
<itemizedlist>
|
||||
<listitem><para>The first line of the commit summarizes the change and begins with the
|
||||
name of the affected package or packages.
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||||
However, not all changes apply to specific packages.
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||||
Consequently, the prefix could also be a machine name or class name.</para></listitem>
|
||||
<listitem><para>The second part of the commit (if needed) is a longer more detailed
|
||||
description of the changes.
|
||||
Placing a blank line between the first and second parts helps with
|
||||
readability.</para></listitem>
|
||||
</itemizedlist>
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Following is an example commit:
|
||||
<literallayout class='monospaced'>
|
||||
bitbake/data.py: Add emit_func() and generate_dependencies() functions
|
||||
|
||||
These functions allow generation of dependency data between functions and
|
||||
variables allowing moves to be made towards generating checksums and allowing
|
||||
use of the dependency information in other parts of BitBake.
|
||||
|
||||
Signed-off-by: Richard Purdie richard.purdie@linuxfoundation.org
|
||||
</literallayout>
|
||||
</para>
|
||||
|
||||
<para>
|
||||
All commits should be self-contained such that they leave the
|
||||
metadata in a consistent state that builds both before and after the
|
||||
commit is made.
|
||||
Besides being a good practice to follow, it helps ensure autobuilder test results
|
||||
are valid.
|
||||
</para>
|
||||
</section>
|
||||
|
||||
<section id="usingpoky-changes-prbump">
|
||||
<title>Package Revision Incrementing</title>
|
||||
|
||||
<para>
|
||||
If a committed change results in changing the package output,
|
||||
then the value of the
|
||||
<filename><link linkend='var-PR'>PR</link></filename> variable needs to be increased
|
||||
(or "bumped") as part of that commit.
|
||||
This means that for new recipes you must be sure to add the <filename>PR</filename>
|
||||
variable and set its initial value equal to "r0".
|
||||
Failing to define <filename>PR</filename> makes it easy to miss when you bump a package.
|
||||
Note that you can only use integer values following the "r" in the
|
||||
<filename>PR</filename> variable.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
If you are sharing a common <filename>.inc</filename> file with multiple recipes,
|
||||
you can also use the
|
||||
<filename><link linkend='var-INC_PR'>INC_PR</link></filename> variable to ensure that
|
||||
the recipes sharing the <filename>.inc</filename> file are rebuilt when the
|
||||
<filename>.inc</filename> file itself is changed.
|
||||
The <filename>.inc</filename> file must set <filename>INC_PR</filename>
|
||||
(initially to "r0"), and all recipes referring to it should set <filename>PR</filename>
|
||||
to "$(INC_PR).0" initially, incrementing the last number when the recipe is changed.
|
||||
If the <filename>.inc</filename> file is changed then its
|
||||
<filename>INC_PR</filename> should be incremented.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
When upgrading the version of a package, assuming the
|
||||
<filename><link linkend='var-PV'>PV</link></filename> changes,
|
||||
the <filename>PR</filename> variable should be reset to "r0"
|
||||
(or "$(INC_PR).0" if you are using <filename>INC_PR</filename>).
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Usually, version increases occur only to packages.
|
||||
However, if for some reason <filename>PV</filename> changes but does not
|
||||
increase, you can increase the
|
||||
<filename><link linkend='var-PE'>PE</link></filename> variable (Package Epoch).
|
||||
The <filename>PE</filename> variable defaults to "0".
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Version numbering strives to follow the
|
||||
<ulink url='http://www.debian.org/doc/debian-policy/ch-controlfields.html'>
|
||||
Debian Version Field Policy Guidelines</ulink>.
|
||||
These guidelines define how versions are compared and what "increasing" a version means.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
There are two reasons for following the previously mentioned guidelines.
|
||||
First, to ensure that when a developer updates and rebuilds, they get all the changes to
|
||||
the repository and do not have to remember to rebuild any sections.
|
||||
Second, to ensure that target users are able to upgrade their
|
||||
devices using package manager commands such as <filename>opkg upgrade</filename>
|
||||
(or similar commands for dpkg/apt or rpm-based systems).
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The goal is to ensure the Yocto Project has packages that can be upgraded in all cases.
|
||||
</para>
|
||||
</section>
|
||||
|
||||
<section id="usingpoky-changes-collaborate">
|
||||
<title>Using The Yocto Project in a Team Environment</title>
|
||||
|
||||
<para>
|
||||
It might not be immediately clear how you can use the Yocto Project in a team environment,
|
||||
or scale it for a large team of developers.
|
||||
The specifics of any situation determine the best solution.
|
||||
Granted that the Yocto Project offers immense flexibility regarding this, practices do exist
|
||||
that experience has shown work well.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The core component of any development effort with the Yocto Project is often an
|
||||
automated build and testing framework along with an image generation process.
|
||||
You can use these core components to check that the metadata can be built,
|
||||
highlight when commits break the build, and provide up-to-date images that
|
||||
allow developers to test the end result and use it as a base platform for further
|
||||
development.
|
||||
Experience shows that buildbot is a good fit for this role.
|
||||
What works well is to configure buildbot to make two types of builds:
|
||||
incremental and full (from scratch).
|
||||
See <ulink url='http://www.yoctoproject.org:8010'>the buildbot for the
|
||||
Yocto Project</ulink> for an example implementation that uses buildbot.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
You can tie incremental builds to a commit hook that triggers the build
|
||||
each time a commit is made to the metadata.
|
||||
This practice results in useful acid tests that determine whether a given commit
|
||||
breaks the build in some serious way.
|
||||
Associating a build to a commit can catch a lot of simple errors.
|
||||
Furthermore, the tests are fast so developers can get quick feedback on changes.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Full builds build and test everything from the ground up.
|
||||
These types of builds usually happen at predetermined times like during the
|
||||
night when the machine load is low.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Most teams have many pieces of software undergoing active development at any given time.
|
||||
You can derive large benefits by putting these pieces under the control of a source
|
||||
control system that is compatible with the Yocto Project (i.e. Git or Subversion (SVN).
|
||||
You can then set the autobuilder to pull the latest revisions of the packages
|
||||
and test the latest commits by the builds.
|
||||
This practice quickly highlights issues.
|
||||
The Yocto Project easily supports testing configurations that use both a
|
||||
stable known good revision and a floating revision.
|
||||
The Yocto Project can also take just the changes from specific source control branches.
|
||||
This capability allows you to track and test specific changes.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Perhaps the hardest part of setting this up is defining the software project or
|
||||
the Yocto Project metadata policies that surround the different source control systems.
|
||||
Of course circumstances will be different in each case.
|
||||
However, this situation reveals one of the Yocto Project's advantages -
|
||||
the system itself does not
|
||||
force any particular policy on users, unlike a lot of build systems.
|
||||
The system allows the best policies to be chosen for the given circumstances.
|
||||
</para>
|
||||
</section>
|
||||
|
||||
<section id="usingpoky-changes-updatingimages">
|
||||
<title>Updating Existing Images</title>
|
||||
|
||||
<para>
|
||||
Often, rather than re-flashing a new image, you might wish to install updated
|
||||
packages into an existing running system.
|
||||
You can do this by first sharing the <filename>tmp/deploy/ipk/</filename> directory
|
||||
through a web server and then by changing <filename>/etc/opkg/base-feeds.conf</filename>
|
||||
to point at the shared server.
|
||||
Following is an example:
|
||||
<literallayout class='monospaced'>
|
||||
$ src/gz all http://www.mysite.com/somedir/deploy/ipk/all
|
||||
$ src/gz armv7a http://www.mysite.com/somedir/deploy/ipk/armv7a
|
||||
$ src/gz beagleboard http://www.mysite.com/somedir/deploy/ipk/beagleboard
|
||||
</literallayout>
|
||||
</para>
|
||||
</section>
|
||||
</section>
|
||||
|
||||
<section id="usingpoky-modifing-packages">
|
||||
<title>Modifying Package Source Code</title>
|
||||
<para>
|
||||
|
|
@ -1300,7 +983,7 @@
|
|||
important files that contain the license text for the source code.
|
||||
It is possible to specify a checksum for an entire file, or a specific section of a
|
||||
file (specified by beginning and ending line numbers with the "beginline" and "endline"
|
||||
parameters respectively).
|
||||
parameters, respectively).
|
||||
The latter is useful for source files with a license notice header,
|
||||
README documents, and so forth.
|
||||
If you do not use the "beginline" parameter, then it is assumed that the text begins on the
|
||||
|
|
@ -1381,6 +1064,325 @@
|
|||
file found in the Yocto Project files area.
|
||||
</para>
|
||||
</section>
|
||||
|
||||
<section id="usingpoky-changes">
|
||||
<title>Making and Maintaining Changes</title>
|
||||
<para>
|
||||
Because the Yocto Project is extremely configurable and flexible,
|
||||
we recognize that developers will want
|
||||
to extend, configure or optimize it for their specific uses.
|
||||
To best keep pace with future Yocto Project changes,
|
||||
we recommend you make controlled changes to the Yocto Project.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The Yocto Project supports a <link linkend='usingpoky-changes-layers'>"layers"</link> concept.
|
||||
If you use layers properly, you can ease future upgrades and allow segregation
|
||||
between the Yocto Project core and a given developer's changes.
|
||||
The following section provides more advice on managing changes to the Yocto Project.
|
||||
</para>
|
||||
|
||||
<section id="usingpoky-changes-layers">
|
||||
<title>BitBake Layers</title>
|
||||
<para>
|
||||
Often, developers want to extend the Yocto Project either by adding packages
|
||||
or by overriding files contained within the Yocto Project to add their own
|
||||
functionality.
|
||||
BitBake has a powerful mechanism called
|
||||
"layers", which provides a way to handle this extension in a fully
|
||||
supported and non-invasive fashion.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The Yocto Project files include several additional layers such as
|
||||
<filename>meta-rt</filename> and <filename>meta-yocto</filename>
|
||||
that demonstrate this functionality.
|
||||
The <filename>meta-rt</filename> layer is not enabled by default.
|
||||
However, the <filename>meta-yocto</filename> layer is.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
To enable a layer, you simply add the layer's path to the
|
||||
<filename><link linkend='var-BBLAYERS'>BBLAYERS</link></filename> variable in your
|
||||
<filename>bblayers.conf</filename> file, which is found in the Yocto Project file's
|
||||
build directory.
|
||||
The following example shows how to enable the <filename>meta-rt</filename>:
|
||||
<literallayout class='monospaced'>
|
||||
LCONF_VERSION = "1"
|
||||
|
||||
BBFILES ?= ""
|
||||
BBLAYERS = " \
|
||||
/path/to/poky/meta \
|
||||
/path/to/poky/meta-yocto \
|
||||
/path/to/poky/meta-rt \
|
||||
"
|
||||
</literallayout>
|
||||
</para>
|
||||
|
||||
<para>
|
||||
BitBake parses each <filename>conf/layer.conf</filename> file for each layer in
|
||||
<filename>BBLAYERS</filename>
|
||||
and adds the recipes, classes and configurations contained within the layer to
|
||||
the Yocto Project.
|
||||
To create your own layer, independent of the Yocto Project files,
|
||||
simply create a directory with a <filename>conf/layer.conf</filename> file and
|
||||
add the directory to your <filename>bblayers.conf</filename> file.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The <filename>meta-yocto/conf/layer.conf</filename> file demonstrates the
|
||||
required syntax:
|
||||
<literallayout class='monospaced'>
|
||||
# We have a conf and classes directory, add to BBPATH
|
||||
BBPATH := "${BBPATH}:${LAYERDIR}"
|
||||
|
||||
# We have a packages directory, add to BBFILES
|
||||
BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb \
|
||||
${LAYERDIR}/recipes-*/*/*.bbappend"
|
||||
|
||||
BBFILE_COLLECTIONS += "yocto"
|
||||
BBFILE_PATTERN_yocto := "^${LAYERDIR}/"
|
||||
BBFILE_PRIORITY_yocto = "5"
|
||||
</literallayout>
|
||||
</para>
|
||||
|
||||
<para>
|
||||
In the previous example, the recipes for the layers are added to
|
||||
<filename><link linkend='var-BBFILES'>BBFILES</link></filename>.
|
||||
The <filename><link linkend='var-BBFILE_COLLECTIONS'>BBFILE_COLLECTIONS</link></filename>
|
||||
variable is then appended with the layer name.
|
||||
The <filename><link linkend='var-BBFILE_PATTERN'>BBFILE_PATTERN</link></filename> variable
|
||||
immediately expands with a regular expression used to match files from
|
||||
<filename>BBFILES</filename> into
|
||||
a particular layer, in this case by using the base pathname.
|
||||
The <filename><link linkend='var-BBFILE_PRIORITY'>BBFILE_PRIORITY</link></filename> variable
|
||||
then assigns different priorities to the files in different layers.
|
||||
Applying priorities is useful in situations where the same package might appear in multiple
|
||||
layers and allows you to choose what layer should take precedence.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Note the use of the <filename><link linkend='var-LAYERDIR'>LAYERDIR</link></filename>
|
||||
variable with the immediate expansion operator.
|
||||
The <filename>LAYERDIR</filename> variable expands to the directory of the current layer and
|
||||
requires the immediate expansion operator so that BitBake does not wait to expand the variable
|
||||
when it's parsing a different directory.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
BitBake can locate where other <filename>.bbclass</filename> and configuration files
|
||||
are applied through the <filename>BBPATH</filename> environment variable.
|
||||
For these cases, BitBake uses the first file with the matching name found in
|
||||
<filename>BBPATH</filename>.
|
||||
This is similar to the way the <filename>PATH</filename> variable is used for binaries.
|
||||
We recommend, therefore, that you use unique <filename>.bbclass</filename>
|
||||
and configuration file names in your custom layer.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
We also recommend the following:
|
||||
<itemizedlist>
|
||||
<listitem><para>Store custom layers in a Git repository that uses the
|
||||
<filename>meta-prvt-XXXX</filename> format.</para></listitem>
|
||||
<listitem><para>Clone the repository alongside other <filename>meta</filename>
|
||||
directories in the Yocto Project source files area.</para></listitem>
|
||||
</itemizedlist>
|
||||
Following these recommendations keeps your Yocto Project files area and
|
||||
its configuration entirely inside the Yocto Project's core base.
|
||||
</para>
|
||||
</section>
|
||||
|
||||
<section id="usingpoky-changes-commits">
|
||||
<title>Committing Changes</title>
|
||||
|
||||
<para>
|
||||
Modifications to the Yocto Project are often managed under some kind of source
|
||||
revision control system.
|
||||
Because some simple practices can significantly improve usability, policy for committing changes
|
||||
is important.
|
||||
It helps to use a consistent documentation style when committing changes.
|
||||
The Yocto Project development team has found the following practices work well:
|
||||
<itemizedlist>
|
||||
<listitem><para>The first line of the commit summarizes the change and begins with the
|
||||
name of the affected package or packages.
|
||||
However, not all changes apply to specific packages.
|
||||
Consequently, the prefix could also be a machine name or class name.</para></listitem>
|
||||
<listitem><para>The second part of the commit (if needed) is a longer more detailed
|
||||
description of the changes.
|
||||
Placing a blank line between the first and second parts helps with
|
||||
readability.</para></listitem>
|
||||
</itemizedlist>
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Following is an example commit:
|
||||
<literallayout class='monospaced'>
|
||||
bitbake/data.py: Add emit_func() and generate_dependencies() functions
|
||||
|
||||
These functions allow generation of dependency data between functions and
|
||||
variables allowing moves to be made towards generating checksums and allowing
|
||||
use of the dependency information in other parts of BitBake.
|
||||
|
||||
Signed-off-by: Richard Purdie richard.purdie@linuxfoundation.org
|
||||
</literallayout>
|
||||
</para>
|
||||
|
||||
<para>
|
||||
All commits should be self-contained such that they leave the
|
||||
metadata in a consistent state that builds both before and after the
|
||||
commit is made.
|
||||
Besides being a good practice to follow, it helps ensure autobuilder test results
|
||||
are valid.
|
||||
</para>
|
||||
</section>
|
||||
|
||||
<section id="usingpoky-changes-prbump">
|
||||
<title>Package Revision Incrementing</title>
|
||||
|
||||
<para>
|
||||
If a committed change results in changing the package output,
|
||||
then the value of the
|
||||
<filename><link linkend='var-PR'>PR</link></filename> variable needs to be increased
|
||||
(or "bumped") as part of that commit.
|
||||
This means that for new recipes you must be sure to add the <filename>PR</filename>
|
||||
variable and set its initial value equal to "r0".
|
||||
Failing to define <filename>PR</filename> makes it easy to miss when you bump a package.
|
||||
Note that you can only use integer values following the "r" in the
|
||||
<filename>PR</filename> variable.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
If you are sharing a common <filename>.inc</filename> file with multiple recipes,
|
||||
you can also use the
|
||||
<filename><link linkend='var-INC_PR'>INC_PR</link></filename> variable to ensure that
|
||||
the recipes sharing the <filename>.inc</filename> file are rebuilt when the
|
||||
<filename>.inc</filename> file itself is changed.
|
||||
The <filename>.inc</filename> file must set <filename>INC_PR</filename>
|
||||
(initially to "r0"), and all recipes referring to it should set <filename>PR</filename>
|
||||
to "$(INC_PR).0" initially, incrementing the last number when the recipe is changed.
|
||||
If the <filename>.inc</filename> file is changed then its
|
||||
<filename>INC_PR</filename> should be incremented.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
When upgrading the version of a package, assuming the
|
||||
<filename><link linkend='var-PV'>PV</link></filename> changes,
|
||||
the <filename>PR</filename> variable should be reset to "r0"
|
||||
(or "$(INC_PR).0" if you are using <filename>INC_PR</filename>).
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Usually, version increases occur only to packages.
|
||||
However, if for some reason <filename>PV</filename> changes but does not
|
||||
increase, you can increase the
|
||||
<filename><link linkend='var-PE'>PE</link></filename> variable (Package Epoch).
|
||||
The <filename>PE</filename> variable defaults to "0".
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Version numbering strives to follow the
|
||||
<ulink url='http://www.debian.org/doc/debian-policy/ch-controlfields.html'>
|
||||
Debian Version Field Policy Guidelines</ulink>.
|
||||
These guidelines define how versions are compared and what "increasing" a version means.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
There are two reasons for following the previously mentioned guidelines.
|
||||
First, to ensure that when a developer updates and rebuilds, they get all the changes to
|
||||
the repository and do not have to remember to rebuild any sections.
|
||||
Second, to ensure that target users are able to upgrade their
|
||||
devices using package manager commands such as <filename>opkg upgrade</filename>
|
||||
(or similar commands for dpkg/apt or rpm-based systems).
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The goal is to ensure the Yocto Project has packages that can be upgraded in all cases.
|
||||
</para>
|
||||
</section>
|
||||
|
||||
<section id="usingpoky-changes-collaborate">
|
||||
<title>Using The Yocto Project in a Team Environment</title>
|
||||
|
||||
<para>
|
||||
It might not be immediately clear how you can use the Yocto Project in a team environment,
|
||||
or scale it for a large team of developers.
|
||||
The specifics of any situation determine the best solution.
|
||||
Granted that the Yocto Project offers immense flexibility regarding this, practices do exist
|
||||
that experience has shown work well.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The core component of any development effort with the Yocto Project is often an
|
||||
automated build and testing framework along with an image generation process.
|
||||
You can use these core components to check that the metadata can be built,
|
||||
highlight when commits break the build, and provide up-to-date images that
|
||||
allow developers to test the end result and use it as a base platform for further
|
||||
development.
|
||||
Experience shows that buildbot is a good fit for this role.
|
||||
What works well is to configure buildbot to make two types of builds:
|
||||
incremental and full (from scratch).
|
||||
See <ulink url='http://www.yoctoproject.org:8010'>the buildbot for the
|
||||
Yocto Project</ulink> for an example implementation that uses buildbot.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
You can tie incremental builds to a commit hook that triggers the build
|
||||
each time a commit is made to the metadata.
|
||||
This practice results in useful acid tests that determine whether a given commit
|
||||
breaks the build in some serious way.
|
||||
Associating a build to a commit can catch a lot of simple errors.
|
||||
Furthermore, the tests are fast so developers can get quick feedback on changes.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Full builds build and test everything from the ground up.
|
||||
These types of builds usually happen at predetermined times like during the
|
||||
night when the machine load is low.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Most teams have many pieces of software undergoing active development at any given time.
|
||||
You can derive large benefits by putting these pieces under the control of a source
|
||||
control system that is compatible with the Yocto Project (i.e. Git or Subversion (SVN).
|
||||
You can then set the autobuilder to pull the latest revisions of the packages
|
||||
and test the latest commits by the builds.
|
||||
This practice quickly highlights issues.
|
||||
The Yocto Project easily supports testing configurations that use both a
|
||||
stable known good revision and a floating revision.
|
||||
The Yocto Project can also take just the changes from specific source control branches.
|
||||
This capability allows you to track and test specific changes.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Perhaps the hardest part of setting this up is defining the software project or
|
||||
the Yocto Project metadata policies that surround the different source control systems.
|
||||
Of course circumstances will be different in each case.
|
||||
However, this situation reveals one of the Yocto Project's advantages -
|
||||
the system itself does not
|
||||
force any particular policy on users, unlike a lot of build systems.
|
||||
The system allows the best policies to be chosen for the given circumstances.
|
||||
</para>
|
||||
</section>
|
||||
|
||||
<section id="usingpoky-changes-updatingimages">
|
||||
<title>Updating Existing Images</title>
|
||||
|
||||
<para>
|
||||
Often, rather than re-flashing a new image, you might wish to install updated
|
||||
packages into an existing running system.
|
||||
You can do this by first sharing the <filename>tmp/deploy/ipk/</filename> directory
|
||||
through a web server and then by changing <filename>/etc/opkg/base-feeds.conf</filename>
|
||||
to point at the shared server.
|
||||
Following is an example:
|
||||
<literallayout class='monospaced'>
|
||||
$ src/gz all http://www.mysite.com/somedir/deploy/ipk/all
|
||||
$ src/gz armv7a http://www.mysite.com/somedir/deploy/ipk/armv7a
|
||||
$ src/gz beagleboard http://www.mysite.com/somedir/deploy/ipk/beagleboard
|
||||
</literallayout>
|
||||
</para>
|
||||
</section>
|
||||
</section>
|
||||
|
||||
</chapter>
|
||||
|
||||
<!--
|
||||
|
|
|
|||
Loading…
Reference in New Issue