How to customize kernel configuration with OpenSTLinux and Yocto?

[AJank.2]

Following the tutorial on How to customize the Linux kernel I made steps as below:

1. Create a custom layer.
2. Add it to the build configuration in bblayers.conf.
3. Create a fragment.config with bitbake menuconfig and put it into my-layer/recipes-kernel/linux/linux-stm32mp/5.15/ as the kernel version is 5.15.
4. Create a my-layer/recipes-kernel/linux/linux-stm32mp_%.bbappend file as advised in the tutorial:

FILESEXTRAPATHS:prepend := "${THISDIR}:${THISDIR}/${PN}:"
 
KERNEL_CONFIG_FRAGMENTS:append = "${WORKDIR}/fragments/${LINUX_VERSION}/fragment-custom.config"
SRC_URI:append = " file://${LINUX_VERSION}/fragment-custom.config;subdir=fragments "

It seems that the kernel configuration wasn't applied at all, is there something that I'm doing wrong?

Without the FILEXTRAPATHS line, the file couldn't be found, yocto didn't look into my-layer at all.

[AJank.2]

Well, if the file /tmp-glibc/work/stm32mp13_rt-ostl-linux-gnueabi/linux-stm32mp/5.15.67.rt49-stm32mp-r1-r0/build/.config is equivalent with the final configuration, then changing the layer priority didn't help at all.

[Erwan SZYMANSKI]

OK I continue to test so.

By the way, I confirm that you need the

FILESEXTRAPATHS:prepend := "${THISDIR}/${PN}:"

in your bbappend file, only way to ensure that the path is in the research path of Yocto.

[AJank.2]

Good to know, I think this should be included in your tutorial How to customize the Linux kernel: https://wiki.st.com/stm32mpu/wiki/How_to_customize_the_Linux_kernel

[Erwan SZYMANSKI]

Yes, good remark, we will add it for sure.

By the way, I tested your layer on a standard weston image provided by ST.

It seems that the .config file is well modified in the build repository of Linux.

I give you my steps:

Put the attach layer under layers/meta-st

Then bitbake-layers add-layer ../layers/meta-st/meta-my-layer

Then bitbake linux-stm32mp

Finally, when I check <..>/build-openstlinuxweston-stm32mp15-disco/tmp-glibc/work/stm32mp15_disco-ostl-linux-gnueabi/.config it seems that your fragment is well taken into account.

Can you also double check from your side ?

Kind regards,

Erwan.

PS: I needed to adapt the layer.conf for my environment which is ST native delivery.

[AJank.2]

I'll try that tomorrow, as today my work day is about to finish. There's one thing which I forgot to mention and may be quite important - instead of the disco image/distro/machine, I used the image with the RT patch, which means that meta-st-x-linux-rt layer with the stm32mp13-rt MACHINE were involved as well. Could it be so that the build behaves differently for the RT variant?

The other two things I get constantly are a WARNING message and a NOTE message as below, sorry for not mentioning about these before:

NOTE: ../layers/meta-st/meta-st-openstlinux/recipes-st/images/st-image-resize-initrd.bb: ENABLE_PARTITIONS_IMAGE not enabled2
WARNING: ../layers/meta-st/meta-st-stm32mp/recipes-kernel/linux/linux-stm32mp_5.15.bb:do_compile is tainted from a forced run

I'm not sure what "tainted" from a forced run means, this are messages run after bitbake st-image-weston.

Okay, thank you for your help, as mentioned already, I'll test your advice tomorrow.

[Erwan SZYMANSKI]

OK thanx for the additional information.

Let me know tomorrow when you will have done your tests.

Kind regards,

Erwan.

[AJank.2]

I just followed your steps and reproduced the fixes, indeed I can already see the config in tmp-glibc/work/stm32mp13_disco-ostl-linux-gnueabi/linux-stm32mp/5.15.67-stm32mp-r2-r0/build/.config. However I do have a few questions.

Beforehand I was building the st-image-weston, your advice says differently. Is there any benefit to using the linux-stm32mp image instead of st-image-weston, what's the difference between them? Actually, is that even an image? The contents of meta-st-stm32mp/recipes-kernel/linux/linux-stm32mp_5.15.bb do look like an image recipe, but it doesn't live in an image directory as it's usually the case. However there's plenty of images in meta-st-stm32mp layer, but in the meta-st-stm32mp/recipes-st/images directory. So I'm a bit confused, can you explain?

Also, how does that linux-stm32mp differ from the st-image-weston?

[Erwan SZYMANSKI]

Hello @Antoni Jankowski​ ,

Sure, this is just to win some time :)

Indeed, I just build the Linux kernel recipe when I do this manipulation, because it saves me some time instead of compiling all the weston image. I just wanted to check and give you a quick answer.

Of course, building only the Linux recipe does not create you your final image. But when you compile st-image-weston it will also compile linux-stm32mp recipe.

So, in conclusion, you should be able to see the same .config generated when you do a bitbake st-image-weston (if not, there is an issue in the Yocto compilation).

Kind regards,

Erwan.

[AJank.2]

Okay, I'll check with the full st-image-weston and get back to you. There's a lot of checking to be happening today :(

[Erwan SZYMANSKI]

Sure, let me know.

If you still does not see it at the very end, maybe make a try with putting your fragment in the x-linux-rt recipe to see if it changes something (because I do not have it on my baseline).

Kind regards,

Erwan.