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kernel-dev: Added new "in-tree" defconfig file section. 

I added the new section "Using an "In-Tree" defconfig File"
section.  This section addresses the ability to not use the
default location for defconfig files, which is usually in the
metadata layer.  The section describes how to use the
KBUILD_DEFCONFIG variable.

Fixes [YOCTO #7474]

(From yocto-docs rev: d68f7b47d974d94177b344247056778742f57786)

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 16:31:42 -06:00 committed by Richard Purdie
parent 540b8ef0f7
commit f9df1a4473
1 changed files with 59 additions and 0 deletions
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documentation/kernel-dev/kernel-dev-common.xml
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@ -238,6 +238,65 @@
section in the Yocto Project Development Manual.
</para>
</section>
<section id='using-an-in-tree-defconfig-file'>
<title>Using an "In-Tree"&nbsp;&nbsp;<filename>defconfig</filename> File</title>
<para>
It might be desirable to have kernel configuration fragment
support through a <filename>defconfig</filename> file that
is pulled from the kernel source tree for the configured
machine.
By default, the OpenEmbedded build system looks for
<filename>defconfig</filename> files in the layer used for
Metadata, which is "out-of-tree", and then configures them
using the following:
<literallayout class='monospaced'>
SRC_URI += "file://defconfig"
</literallayout>
If you do not want to maintain copies of
<filename>defconfig</filename> files in your layer but would
rather allow users to use the default configuration from the
kernel tree and still be able to add configuration fragments
to the
<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
through, for example, append files, you can direct the
OpenEmbedded build system to use a
<filename>defconfig</filename> file that is "in-tree".
</para>
<para>
To specify an "in-tree" <filename>defconfig</filename> file,
edit the recipe that builds your kernel so that it has the
following command form:
<literallayout class='monospaced'>
KBUILD_DEFCONFIG_<ulink url='&YOCTO_DOCS_REF_URL;#var-KMACHINE'>KMACHINE</ulink> ?= <replaceable>defconfig_file</replaceable>
</literallayout>
You need to append the variable with
<filename>KMACHINE</filename> and then supply the path to
your "in-tree" <filename>defconfig</filename> file.
</para>
<para>
Aside from modifying your kernel recipe and providing your own
<filename>defconfig</filename> file, you need to be sure no
files or statements set <filename>SRC_URI</filename> to use a
<filename>defconfig</filename> other than your "in-tree"
file (e.g. a kernel's <filename>linux-</filename><replaceable>machine</replaceable><filename>.inc</filename>
file).
In other words, if the build system detects a statement
that identifies an "out-of-tree"
<filename>defconfig</filename> file, that statement
will override your
<filename>KBUILD_DEFCONFIG</filename> variable.
</para>
<para>
See the
<ulink url='&YOCTO_DOCS_REF_URL;#var-KBUILD_DEFCONFIG'><filename>KBUILD_DEFCONFIG</filename></ulink>
variable description for more information.
</para>
</section>
</section>
<section id='using-an-iterative-development-process'>