[meta-freescale] Problems about selecting linux kernel drivers.

[Andrey Zhizhikin]

On Wed, Nov 20, 2019 at 3:14 PM Yusuf Altıparmak
<yusufalti1997 at gmail.com> wrote:
>
>
>> Hello Yusuf,
>>     You should be careful when generating kernel config file. Yocto project override kernel config(.config file) when compiling again.
>>
>
> Hello Atakan,
>
> I solved that problem by changing the defconfig source string in <machine>.conf file. Each time I make changes, I also copy new .config file to another folder and rename it as in <machine>.conf file. My <machine>.conf(t1042d4rdb-64b.conf) file is like this;
> KERNEL_DEFCONFIG ?= "${S}/arch/powerpc/configs/yusuf_defconfig"
> KBUILD_DEFCONFIG ?= "yusuf_defconfig"

This approach has 2 problems:
1. .config file is not the same as defconfig file. .config is
auto-generated from whatever the defconfig you supply.
2. keeping the config file in the kernel tree implies you have to
maintain your own kernel repository, or pollute it with unnecessary
copy operation during kernel build

To solve those problems you can do the following:
1. bitbake virtual/kernel -c savedefconfig would give you a defconfig
file which is a real defconfig.
2. keep this defconfig next to the kernel recipe, and set
KBUILD_DEFCONFIG to the one you generated at the step 1. above

In this case you would not need to keep your kernel tree, have a
"clean" defconfig file on hands which you can always update, and have
a very nice tidy kernel recipe to build.

Also, add to your kernel recipe following lines:
FILESEXTRAPATHS_prepend := "${THISDIR}/${BPN}:"
SRC_URI += "file://yusuf_defconfig"

This would ensure that your yusuf_defconfig could be found and used
for the build. ${BPN} is the kernel recipe name, so you would need to
create a folder named as your kernel recipe next to the recipe itself
and store the config file there.

>
> Best Regards
>
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-- 
Regards,
Andrey.