2.2.4. Using an "In-Tree"  defconfig File

It might be desirable to have kernel configuration fragment support through a defconfig file that is pulled from the kernel source tree for the configured machine. By default, the OpenEmbedded build system looks for defconfig files in the layer used for Metadata, which is "out-of-tree", and then configures them using the following:

     SRC_URI += "file://defconfig"
                

If you do not want to maintain copies of defconfig 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 SRC_URI through, for example, append files, you can direct the OpenEmbedded build system to use a defconfig file that is "in-tree".

To specify an "in-tree" defconfig file, edit the recipe that builds your kernel so that it has the following command form:

     KBUILD_DEFCONFIG_KMACHINE ?= defconfig_file
                

You need to append the variable with KMACHINE and then supply the path to your "in-tree" defconfig file.

Aside from modifying your kernel recipe and providing your own defconfig file, you need to be sure no files or statements set SRC_URI to use a defconfig other than your "in-tree" file (e.g. a kernel's linux-machine.inc file). In other words, if the build system detects a statement that identifies an "out-of-tree" defconfig file, that statement will override your KBUILD_DEFCONFIG variable.

See the KBUILD_DEFCONFIG variable description for more information.