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documentation/kernel-manual/kernel-how-to.xml: Partial - Re-write of BSP creation

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This is a partial edit of re-writing the BSP creation section so that
it is clearer for the naive user.  It is not quite done yet.

(From yocto-docs rev: 7a552e72a1d2d1b6ffa93f4fe3074f318ff35715)

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
2011-07-01 13:35:10 -07:00
committed by Richard Purdie
parent 1316648ae6
commit fe438753ba
1 changed files with 60 additions and 40 deletions
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documentation/kernel-manual/kernel-how-to.xml
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@@ -1021,62 +1021,76 @@ That's it. Configure and build.
</para> </para>
<para> <para>
You can start with something in <filename>meta/conf/machine</filename> - <filename> You can start with a machine configuration file in the Yocto Project source tree
meta/conf/machine/atom-pc.conf</filename> for example. Or, you can start with a machine such as the <filename>atom-pc.conf</filename> in <filename>meta-yocto/conf/machine</filename>.
configuration from any of the BSP layers in the meta-intel repository at Or, you can start with a machine configuration file from a BSP layer
<ulink url='http://git.yoctoproject.org/cgit/cgit.cgi/meta-intel/'></ulink>, such as such as <filename>emenlow.conf</filename> in <filename>meta-emenlow/conf/machine</filename>.
<filename>meta-intel/meta-emenlow/conf/machine/emenlow.conf</filename>.
</para> </para>
<para> <para>
The main difference between the two is that "emenlow" is in its own layer. The main difference between these two BSP machine configuration files is that "emenlow" is
It is in its own layer because it needs extra machine-specific packages such as its in its own isolated BSP layer, while "atom-pc" is in a more encompassing layer
own video driver and other supporting packages. named <filename>meta-yocto</filename> that is part of the Yocto Project source tree.
The "atom-pc" is simpler and does not need any special packages - everything it needs can The "emenlow" configuration is in its own BSP layer because the target hardware
be specified in the configuration file. needs extra machine-specific packages to support graphics and other features.
The "atom-pc" configuration file supports more basic hardware that does not need any
special packages - everything the hardware needs can be specified in the configuration file.
The "atom-pc" machine also supports all of Asus eee901, Acer Aspire One, Toshiba NB305, The "atom-pc" machine also supports all of Asus eee901, Acer Aspire One, Toshiba NB305,
and the Intel&reg; Embedded Development Board 1-N450 with no changes. and the Intel&reg; Embedded Development Board 1-N450 with no changes.
</para> </para>
<para> <para>
If you want to make minor changes to support a slightly different machine, you can If you want to make minor changes to support a slightly different machine, you can
create a new configuration file for it and add it alongside the others. create a new configuration file for the new machine and add it alongside the
You might consider keeping the common information separate and including it. configuration files.
You might consider keeping common configurations for several machines in a separate file
and then including the other configuration files that have more specific configurations.
</para> </para>
<para> <para>
Similarly, you can also use multiple configuration files for different machines even Similarly, you can also use multiple configuration files for different machines even
if you do it as a separate layer like meta-emenlow. when the configuration files come from a separate and different layer.
</para> </para>
<para> <para>
As an example consider this: As an example consider this:
<itemizedlist> <orderedlist>
<listitem><para>Copy meta-emenlow to meta-mymachine</para></listitem> <listitem><para>Copy the "emenlow" BSP layer to a new BSP layer named
<listitem><para>Fix or remove anything you do not need. <filename>meta-mymachine</filename>.
For this example the only thing left was the kernel directory with a Now you have two identical BSP layers &dash; but with different names.</para></listitem>
<filename>linux-yocto_git.bbappend</filename> <listitem><para>This example assumes you only need to change some machine
file configurations and inform the Yocto Project build process of the new layer.
and <filename>meta-mymachine/conf/machine/mymachine.conf</filename> Consequently, modify the new layer's structure so that all it contains
(linux-yocto is the kernel listed in is the <filename>linux-yocto_git.bbappend</filename> file in the
<filename>meta-emenlow/conf/machine/emenlow.conf</filename>)</para></listitem>. <filename>meta-mymachine/recipes-kernel/linux</filename> directory
<listitem><para>Add a new entry in the <filename>build/conf/bblayers.conf</filename> and the <filename>emenlow.conf</filename> configuration file in the
so the new layer can be found by BitBake.</para></listitem> <filename>meta-mymachine/conf/machine</filename> directory.
</itemizedlist> Note that "linux-yocto" is the kernel specified in the <filename>mymachine.conf</filename>
configuration file.</para></listitem>.
<listitem><para>Rename the <filename>emenlow.conf</filename> file to <filename>mymachine.conf</filename>
and fix or remove any configurations.</para></listitem>
<listitem><para>Make sure the Yocto Project build process knows about the new BSP
layer by adding the layer to the <filename>bblayers.conf</filename> configuration
file located in the Yocto Project build tree at <filename>build/conf/bblayers.conf</filename>.
Adding the layer allows Bitbake to find the new layer.
You also need to edit the <filename>layer.conf</filename> file located in the
<filename>meta-mymachine/conf</filename> directory such that "mymachine" replaces
"emenlow".</para></listitem>
</orderedlist>
</para></listitem> </para></listitem>
<listitem><para> <listitem><para>
Create a machine branch for your machine. Create a machine branch for your machine in a the Yocto Project git repository.
</para> </para>
<para> <para>
For the kernel to compile successfully, you need to create a branch in the git repository For the kernel to compile successfully, you need to create a branch in the
specifically named for your machine. Yocto Project git repository that is specifically named for your machine.
To create this branch first create a bare clone of the Yocto Project git repository. To create this branch, first create a bare clone of the Yocto Project git repository.
Next, create a local clone of that: Then, create a local clone of that bare clone.
Here are the commands:
<literallayout class='monospaced'> <literallayout class='monospaced'>
$ git clone --bare git://git.yoctoproject.org/linux-yocto-2.6.37.git $ git clone --bare git://git.yoctoproject.org/linux-yocto-2.6.37.git linux-yocto-2.6.37.git
linux-yocto-2.6.37.git
$ git clone linux-yocto-2.6.37.git linux-yocto-2.6.37 $ git clone linux-yocto-2.6.37.git linux-yocto-2.6.37
</literallayout> </literallayout>
</para> </para>
@@ -1090,8 +1104,12 @@ That's it. Configure and build.
</para></listitem> </para></listitem>
<listitem><para> <listitem><para>
In a layer, create a <filename>linux-yocto_git.bbappend</filename> In your new layer you need to edit the <filename>linux-yocto_git.bbappend</filename>
file with the following: file so that the compatible machine is "mymachine".
It is also convenient point to a cloned Yocto Project git repository that is local
to your system for development purposes.
Thus, change the <filename>linux-yocto_git.bbappend</filename> file in your
<filename>meta-mymachine</filename> layer to the following:
</para> </para>
<para> <para>
@@ -1099,11 +1117,11 @@ That's it. Configure and build.
FILESEXTRAPATHS := "${THISDIR}/${PN}" FILESEXTRAPATHS := "${THISDIR}/${PN}"
COMPATIBLE_MACHINE_mymachine = "mymachine" COMPATIBLE_MACHINE_mymachine = "mymachine"
# It is often nice to have a local clone of the kernel repository, to # It is often nice to have a clone of the kernel repository, to
# allow patches to be staged, branches created, and so forth. Modify # allow patches to be staged, branches created, and so forth. Modify
# KSRC to point to your local clone as appropriate. # KSRC to point to your bare clone as appropriate.
KSRC ?= /path/to/your/bare/clone/for/example/linux-yocto-2.6.37.git KSRC ?= $MYWORK/linux-yocto-2.6.37.git
# KMACHINE is the branch to be built, or alternatively # KMACHINE is the branch to be built, or alternatively
# KBRANCH can be directly set. # KBRANCH can be directly set.
@@ -1117,7 +1135,9 @@ That's it. Configure and build.
</para> </para>
<para> <para>
After doing that, select the machine in <filename>build/conf/local.conf</filename>: After updating the <filename>linux-yocto_git.bbappend</filename> file,
edit the <filename>build/conf/local.conf</filename> found
in the Yocto Project build tree so that it selects your machine:
<literallayout class='monospaced'> <literallayout class='monospaced'>
# #
MACHINE ?= "mymachine" MACHINE ?= "mymachine"
@@ -1137,7 +1157,7 @@ That's it. Configure and build.
</para> </para>
<para> <para>
Of course, that will give you a kernel with the default configuration file, which is probably At this point you will build a kernel with the default configuration file, which is probably
not what you want. not what you want.
If you just want to set some kernel configuration options, you can do that by If you just want to set some kernel configuration options, you can do that by
putting them in a file. putting them in a file.
@@ -1155,7 +1175,7 @@ That's it. Configure and build.
</literallayout> </literallayout>
<para> <para>
These config fragments could then be picked up and These configuration fragments could then be picked up and
applied to the kernel .config by appending them to the kernel SRC_URI: applied to the kernel .config by appending them to the kernel SRC_URI:
</para> </para>