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kernel-dev: Updated Tree Construction section

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The section was using the "meta-*" stuff, which is not how it
is done any longer.

(From yocto-docs rev: c9d95e85a832a38c3fd099a728693af3fa708d50)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark
2017-10-03 12:06:51 -07:00
committed by Richard Purdie
parent f83991dc04
commit 766770aa35
1 changed files with 100 additions and 57 deletions
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157
documentation/kernel-dev/kernel-dev-maint-appx.xml
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@@ -22,11 +22,13 @@
Those feature descriptions list all necessary patches,
configurations, branches, tags, and feature divisions found in a
Yocto Linux kernel.
Thus, the Yocto Project Linux kernel repository (or tree) is built.
Thus, the Yocto Project Linux kernel repository (or tree) and
accompanying Metadata in the
<filename>yocto-kernel-cache</filename> are built.
</para>
<para>
The existence of this tree allows you to access and clone a
The existence of these repositories allow you to access and clone a
particular Yocto Project Linux kernel repository and use it to
build images based on their configurations and features.
</para>
@@ -34,12 +36,16 @@
<para>
You can find the files used to describe all the valid features and
BSPs in the Yocto Project Linux kernel in any clone of the Yocto
Project Linux kernel source repository Git tree.
For example, the following command clones the Yocto Project
Project Linux kernel source repository and
<filename>yocto-kernel-cache</filename> Git trees.
For example, the following commands clone the Yocto Project
baseline Linux kernel that branches off
<filename>linux.org</filename> version 4.12:
<filename>linux.org</filename> version 4.12 and the
<filename>yocto-kernel-cache</filename>, which contains stores of
kernel Metadata:
<literallayout class='monospaced'>
$ git clone git://git.yoctoproject.org/linux-yocto-4.12
$ git clone git://git.yoctoproject.org/linux-kernel-cache
</literallayout>
For more information on how to set up a local Git repository of
the Yocto Project Linux kernel files, see the
@@ -48,25 +54,33 @@
</para>
<para>
Once you have cloned the kernel Git repository on your local
machine, you can discover the branches that are avilable in the
repository using the following Git command:
Once you have cloned the kernel Git repository and the
cache of Metadata on your local machine, you can discover the
branches that are avilable in the repository using the following
Git command:
<literallayout class='monospaced'>
$ git branch -a
</literallayout>
Checking out a branch allows you to work with a particular
Yocto Linux kernel.
For example, the following command checks out the
<filename>standard/beagleboard</filename> branch of the
repository:
For example, the following commands check out the
"standard/beagleboard" branch of the Yocto Linux kernel repository
and the "yocto-4.12" branch of the
<filename>yocto-kernel-cache</filename> repository:
<literallayout class='monospaced'>
$ cd linux-yocto-4.12
$ git checkout -b my-kernel-4.12 standard/beagleboard
$ cd ~/linux-yocto-4.12
$ git checkout -b my-kernel-4.12 remotes/origin/standard/beagleboard
$ cd ~/linux-kernel-cache
$ git checkout -b my-4.12-metadata remotes/origin/yocto-4.12
</literallayout>
Once you have checked out and switched to the
<filename>standard/beagleboard</filename> branch,
<note>
Branches in the <filename>yocto-kernel-cache</filename>
repository correspond to Yocto Linux kernel versions
(e.g. "yocto-4.12", "yocto-4.10", "yocto-4.9", and so forth).
</note>
Once you have checked out and switched to appropriate branches,
you can see a snapshot of all the kernel source files used to
used to build that particular Yocto Linux kernel for that
used to build that particular Yocto Linux kernel for a
particular board.
</para>
@@ -74,9 +88,9 @@
To see the features and configurations for a particular Yocto
Linux kernel, you need to examine the
<filename>yocto-kernel-cache</filename> Git repository.
Branches in the <filename>yocto-kernel-cache</filename> repository
correspond to Yocto Linux kernel versions (e.g.
<filename>yocto-4.12</filename>).
As mentioned, branches in the
<filename>yocto-kernel-cache</filename> repository correspond to
Yocto Linux kernel versions (e.g. <filename>yocto-4.12</filename>).
Branches contain descriptions in the form of
<filename>.scc</filename> and <filename>.cfg</filename> files.
</para>
@@ -106,77 +120,106 @@
(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:
These are the actions that effectively provide the Metadata
and create the tree that includes the new feature, patch or BSP:
<orderedlist>
<listitem><para>
<emphasis>Pass Feature to Build Subsystem:</emphasis>
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>
<emphasis>Locate Feature:</emphasis>
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>yocto-kernel-cache/cfg/kernel-cache</filename>
located in the
<filename>yocto-kernel-cache</filename>
repository
</para></listitem>
<listitem><para>
Areas pointed to by <filename>SRC_URI</filename>
statements found in recipes
statements found in kernel 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:
I AM HERE
<literallayout class='monospaced'>
<replaceable>bsp_name</replaceable>-<replaceable>kernel_type</replaceable>.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.
<listitem><para>
<emphasis>Compile Feature:</emphasis>
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>
<emphasis>Append Extra Features:</emphasis>
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>
variable in recipes.
</para></listitem>
<listitem><para>
<emphasis>Locate, Compile, and Append Each Feature:</emphasis>
Each extra feature is located, compiled and appended to
the script as described in step three.
</para></listitem>
<listitem><para>
<emphasis>Execute the Script:</emphasis>
The script is executed to produce files
<filename>.scc</filename> and <filename>.cfg</filename>
files in appropriate directories of the
<filename>yocto-kernel-cache</filename> repository.
These files 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>
<emphasis>Clone Base Repository:</emphasis>
The base repository is cloned, and the actions
listed in the <filename>yocto-kernel-cache</filename>
irectories are applied to the tree.
</para></listitem>
<listitem><para>
<emphasis>Perform Cleanup:</emphasis>
The Git repositories are left with the desired branches
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 kernel tree and cache are 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>yocto-kernel-cache</filename>
repository adds 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>
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>