[yocto] Kernel configuration patches not persisting?

[Stephano Cetola]

On 4/4/18 7:48 AM, Giordon Stark wrote:
> Hi all,
> 
> I have a custom board with custom kernel config changes. Because of
> that, I append the u-boot recipe as well:
> 
> https://github.com/kratsg/meta-l1calo/blob/master/recipes-bsp/u-boot/u-boot-xlnx_%25.bbappend 
> 
> with my machine.h and defconfig files
> here: https://github.com/kratsg/meta-l1calo/tree/master/recipes-bsp/u-boot/files/gfex-prototype4 
> 
> I find that when I make a change in the defconfig, such as
> "CONFIG_CPU_IDLE=n", bitbake properly recompiles all the necessary
> components... however, when I look at the running kernel configuration:
> 
> root at gfex-prototype4:~# cat /proc/config.gz | gunzip > run.config
> root at gfex-prototype4:~# vi run.config
> root at gfex-prototype4:~# cat run.config | grep CONFIG_CPU_IDLE
> CONFIG_CPU_IDLE=y
> # CONFIG_CPU_IDLE_GOV_LADDER is not set
> CONFIG_CPU_IDLE_GOV_MENU=y
> 
> it seems my change still wasn't propagated? I looked at the instructions
> here
> (https://www.yoctoproject.org/docs/latest/kernel-dev/kernel-dev.html#changing-the-configuration)
> but I'm not sure I want to duplicate my defconfig file into a second
> location to bbappend the linux-yocto.
> 
> Have I done something wrong? Am I missing something else?
> 
> Giordon
> -- 
> Giordon Stark

Hey Giordon,

It looks like you're confusing two topics: u-boot and kernel configuration.

Both u-boot and the kernel use kconfig. This can confuse folks that are
new to bootloader/kernel work.

Looking at your layer, you're actually interested in changing the
kernel's configuration rather than u-boot. For example, on the
gfex-prototype4 defconfig, you set ARCH_ZYNQMP, which is a kernel config
for the Xilinx Zynq boards. You probably want to add a bbappend for your
kernel and add the defconfig to that recipe.

Cheers,
Stephano