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dev-manual, kernel-dev: Moved kernel branch concepts to kernel-dev

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Fixes [YOCTO #11630]

The information in the dev-manual kernel overview area really neeeds
to be in the Appendix on kernel structure in the kernel-dev manual.
I moved that informtaion to the appendix.  Removal of one redundant
image was necessary from the dev-manual.  The figure was literally
repeated in the kernel manual already under a different file name.

(From yocto-docs rev: 00ca68e760e41448c225fb1ca4a77f5201434b93)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark
2017-06-29 13:06:27 -07:00
committed by Richard Purdie
parent bdeb6db2fb
commit 64f0f60b3f
4 changed files with 92 additions and 100 deletions
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documentation/dev-manual/dev-manual-model.xml
+18 -57
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@@ -86,67 +86,26 @@
<title>Kernel Overview</title>
<para>
The kernels are maintained using the Git revision control system
that structures them using the familiar "tree", "branch", and "leaf" scheme.
Branches represent diversions from general code to more specific code, while leaves
represent the end-points for a complete and unique kernel whose source files,
when gathered from the root of the tree to the leaf, accumulate to create the files
necessary for a specific piece of hardware and its features.
The following figure displays this concept:
<para>
<imagedata fileref="figures/kernel-overview-1.png"
width="6in" depth="6in" align="center" scale="100" />
</para>
<para>
Within the figure, the "Kernel.org Branch Point" represents the point in the tree
where a supported base kernel is modified from the Linux kernel.
For example, this could be the branch point for the <filename>linux-yocto-3.19</filename>
kernel.
Thus, everything further to the right in the structure is based on the
<filename>linux-yocto-3.19</filename> kernel.
Branch points to the right in the figure represent where the
<filename>linux-yocto-3.19</filename> kernel is modified for specific hardware
or types of kernels, such as real-time kernels.
Each leaf thus represents the end-point for a kernel designed to run on a specific
targeted device.
</para>
<para>
The overall result is a Git-maintained repository from which all the supported
kernel types can be derived for all the supported devices.
A big advantage to this scheme is the sharing of common features by keeping them in
"larger" branches within the tree.
This practice eliminates redundant storage of similar features shared among kernels.
</para>
<note>
Keep in mind the figure does not take into account all the supported Yocto
Project kernel types, but rather shows a single generic kernel just for conceptual purposes.
Also keep in mind that this structure represents the Yocto Project source repositories
that are either pulled from during the build or established on the host development system
prior to the build by either cloning a particular kernel's Git repository or by
downloading and unpacking a tarball.
</note>
<para>
Upstream storage of all the available kernel source code is one thing, while
representing and using the code on your host development system is another.
Conceptually, you can think of the kernel source repositories as all the
source files necessary for all the supported kernels.
As a developer, you are just interested in the source files for the kernel on
which you are working.
Upstream storage of all the available kernel source code is
one thing, while representing and using the code on your host
development system is another.
Conceptually, you can think of the kernel source repositories
as all the source files necessary for all the supported
Yocto Linux kernels.
As a developer, you are just interested in the source files
for the kernel on which you are working.
And, furthermore, you need them available on your host system.
</para>
<para>
Kernel source code is available on your host system a couple of different
ways.
If you are working in the kernel all the time, you probably would want
to set up your own local Git repository of the kernel tree.
If you just need to make some patches to the kernel, you can access
temporary kernel source files that were extracted and used
during a build.
Kernel source code is available on your host system a couple
of different ways.
If you are working in the kernel all the time, you probably
would want to set up your own local Git repository of the
Yocto Linux kernel tree.
If you just need to make some patches to the kernel, you can
access temporary kernel source files that were extracted and
used during a build.
We will just talk about working with the temporary source code.
For more information on how to get kernel source code onto your
host system, see the
@@ -164,6 +123,8 @@
Thus, in a sense, the process constructs a local source tree specific to your
kernel to generate the new kernel image - a source generator if you will.
</para>
<para>
The following figure shows the temporary file structure
created on your host system when the build occurs.
This
documentation/dev-manual/figures/kernel-overview-1.png
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