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dev-manual: Added new section on "defconfig" files. 

The "Configuring the Kernel" section did not address "defconfig"
files.  In my opinion, this is a hole in the docs for this section.
I added a new section titled "Creating a defconfig File" that is a
sub-section of the "Configuring the Kernel" section.

Additionally, I added a brief sentence in the introductory paragraph
to include the fact that this new information exists.

Finally, I included the bitbake command that ensures that the
proper configuration steps are minimally run before a user attempts
to use bitbake to get into menuconfig.

Fixes [#YOCTO 7474]

(From yocto-docs rev: 13c0c7dddca59474ef65dacc12f0bfaa38933887)

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 2015-05-18 15:12:26 -06:00 committed by Richard Purdie
parent 7b1697bd15
commit 540b8ef0f7
1 changed files with 92 additions and 14 deletions
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106
documentation/dev-manual/dev-manual-common-tasks.xml
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@ -4624,13 +4624,22 @@
<title>Configuring the Kernel</title>
<para>
Configuring the Yocto Project kernel consists of making sure the <filename>.config</filename>
file has all the right information in it for the image you are building.
You can use the <filename>menuconfig</filename> tool and configuration fragments to
make sure your <filename>.config</filename> file is just how you need it.
This section describes how to use <filename>menuconfig</filename>, create and use
configuration fragments, and how to interactively modify your <filename>.config</filename>
file to create the leanest kernel configuration file possible.
Configuring the Yocto Project kernel consists of making sure the
<filename>.config</filename> file has all the right information
in it for the image you are building.
You can use the <filename>menuconfig</filename> tool and
configuration fragments to make sure your
<filename>.config</filename> file is just how you need it.
You can also save known configurations in a
<filename>defconfig</filename> file that the build system can use
for kernel configuration.
</para>
<para>
This section describes how to use <filename>menuconfig</filename>,
create and use configuration fragments, and how to interactively
modify your <filename>.config</filename> file to create the
leanest kernel configuration file possible.
</para>
<para>
@ -4660,18 +4669,23 @@
<ulink url='&YOCTO_DOCS_REF_URL;#structure-memres-core-script'><filename>oe-init-build-env-memres</filename></ulink>
script found in the
<link linkend='build-directory'>Build Directory</link>.
The following commands run <filename>menuconfig</filename> assuming the
<link linkend='source-directory'>Source Directory</link>
top-level folder is <filename>~/poky</filename>:
You must also be sure of the state of your build in the
<link linkend='source-directory'>Source Directory</link>.
The following commands run <filename>menuconfig</filename>
assuming the Source Directory's top-level folder is
<filename>~/poky</filename>:
<literallayout class='monospaced'>
$ cd poky
$ source oe-init-build-env
$ bitbake linux-yocto -c kernel_configme -f
$ bitbake linux-yocto -c menuconfig
</literallayout>
Once <filename>menuconfig</filename> comes up, its standard interface allows you to
interactively examine and configure all the kernel configuration parameters.
After making your changes, simply exit the tool and save your changes to
create an updated version of the <filename>.config</filename> configuration file.
Once <filename>menuconfig</filename> comes up, its standard
interface allows you to interactively examine and configure
all the kernel configuration parameters.
After making your changes, simply exit the tool and save your
changes to create an updated version of the
<filename>.config</filename> configuration file.
</para>
<para>
@ -4752,6 +4766,70 @@
</para>
</section>
<section id='creating-a-defconfig-file'>
<title>Creating a&nbsp;&nbsp;<filename>defconfig</filename> File</title>
<para>
A <filename>defconfig</filename> file is simply a
<filename>.config</filename> renamed to "defconfig".
You can use a <filename>defconfig</filename> file
to retain a known set of kernel configurations from which the
OpenEmbedded build system can draw to create the final
<filename>.config</filename> file.
<note>
Out-of-the-box, the Yocto Project never ships a
<filename>defconfig</filename> or
<filename>.config</filename> file.
The OpenEmbedded build system creates the final
<filename>.config</filename> file used to configure the
kernel.
</note>
</para>
<para>
To create a <filename>defconfig</filename>, start with a
complete, working Linux kernel <filename>.config</filename>
file.
Copy that file to the appropriate
<filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-PN'><filename>PN</filename></ulink><filename>}</filename>
directory in your layer's
<filename>recipes-kernel/linux</filename> directory, and rename
the copied file to "defconfig".
Then, add the following lines to the linux-yocto
<filename>.bbappend</filename> file in your layer:
<literallayout class='monospaced'>
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
SRC_URI += "file://defconfig"
</literallayout>
The
<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
tells the build system how to search for the file, while the
<ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink>
extends the
<ulink url='&YOCTO_DOCS_REF_URL;#var-FILESPATH'><filename>FILESPATH</filename></ulink>
variable (search directories) to include the
<filename>${PN}</filename> directory you created to hold the
configuration changes.
<note>
The build system applies the configurations from the
<filename>defconfig</filename> file before applying any
subsequent configuration fragments.
The final kernel configuration is a combination of the
configurations in the <filename>defconfig</filename>
file and any configuration fragments you provide.
You need to realize that if you have any configuration
fragments, the build system applies these on top of and
after applying the existing defconfig file configurations.
</note>
For more information on configuring the kernel, see the
"<ulink url='&YOCTO_DOCS_KERNEL_DEV_URL;#changing-the-configuration'>Changing the Configuration</ulink>"
and
"<ulink url='&YOCTO_DOCS_KERNEL_DEV_URL;#generating-configuration-files'>Generating Configuration Files</ulink>"
sections, both in the Yocto Project Linux Kernel Development
Manual.
</para>
</section>
<section id='creating-config-fragments'>
<title>Creating Configuration Fragments</title>