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| -rw-r--r-- | documentation/kernel-dev/kernel-dev-common.xml | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/documentation/kernel-dev/kernel-dev-common.xml b/documentation/kernel-dev/kernel-dev-common.xml index c0acac8316..618d60cbaf 100644 --- a/documentation/kernel-dev/kernel-dev-common.xml +++ b/documentation/kernel-dev/kernel-dev-common.xml @@ -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" <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'> |