[yocto] kconfig variables not being included in yocto build.

[Sakib Sajal]

Hello,

I have been trying to patch the linux kernel and add some kernel configuration but I am failing to add kconfig fragments to be included in the final build.

Initially I tried patching the kernel with hardcoded values in the patch.

I am building for qemu to minimize the variables I have to worry about.

Build Configuration:
BB_VERSION           = "1.38.0"
BUILD_SYS            = "x86_64-linux"
NATIVELSBSTRING      = "ubuntu-16.04"
TARGET_SYS           = "i586-poky-linux"
MACHINE              = "qemux86"
DISTRO               = "poky"
DISTRO_VERSION       = "2.5.1"         // branch "sumo"
TUNE_FEATURES        = "m32 i586"
TARGET_FPU           = ""


My initial project structure:

-poky
--meta
--meta-poky
--meta-yocto-bsp
--meta-my-layer
---recipes-kernel
----linux
-----linux-yocto
------my-patch.patch
-----linux-yocto_4%.bbappend
---conf
----layer.conf

Content of the bbappend file:
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"

SRC_URI += "file://my-patch.patch"

I enabled my-layer by adding the layer in the build/conf/bblayers.conf file. I was able to build an image and test my changes with the hardcoded valued in my patch.

However I want the values to be configurable through kernel configuration. Since I knew what variables I have introduced, I put them in a .cfg file with their desired values in the linux-yocto folder.

New project structure:

-poky
--meta-my-layer
---recipes-kernel
----linux
-----linux-yocto
------my-conf-frag.cfg

(other files and directories are same as before)

Added the following line to the .bbappend file:
SRC_URI += "file://my-conf-frag.cfg"

Content of my-conf-frag.cfg:
CONFIG_MY_FIRST_VAR="MY-NAME"
CONFIG_MY_SECOND_VAR=y

Then I run:
bitbake core-image-base

and get the following error:

ERROR: Task (<work_dir>/poky/meta/recipes-kernel/linux/linux-yocto_4.14.bb:do_compile) failed with exit code '1'

The kernel isn't being compiled since it does not know what "CONFIG_MY_FIRST_VAR" is.

I checked for .config files in the build directory and found one in "poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/cfg/.config" which contained the two variables I defined in my cfg file. But that file is a kernel configuration fragment file itself. The final config file which is used to build the image is located, I believe, in "poky/build/tmp/work/qemux86-poky-linux/linux-yocto/4.14.67+gitAUTOINC+c43c9e19a2_084af9624d-r0/linux-qemux86-standard-build/.config" but i do not see the variables there in the final .config file. I was also able to locate the cfg and the patch file in "/poky/build/tmp/work/qemux86-poky-linux/linux-yocto/4.14.67+gitAUTOINC+c43c9e19a2_084af9624d-r0/"directory. Therefore the files are being picked up by the build system but the fragments are not being applied to make the final .config file used to build the kernel.

I went through yocto mailing list for similar problems and followed the steps provided with no success. I also went through yocto's mega-manual and kernel development manual as well as the yocto-lab pdfs and followed all the different steps but i always get the compilation error.

Can someone please help me. Thanks in advance!

Sakib Sajal

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