[Buildroot] Please help me on kernel configuration with rt-patch applied

[Andreas Ziegler]

Ciao Matteo,

> Hello,
> 
> 
> I'm facing a strange issue on kernel configuration with rt-patch 
> applied.
> 
> 
> I'm using buildroot-2020.02.8 with kernel 5.4.78 and rt-patch
> 5.4.78-rt44, patch is applied through BR2_GLOBAL_PATCH_DIR variable
> and custom kernel configuration that takes it into account is passed
> through BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE variable.
> 
> 
> Patch is correctly applied and above configuration file is copied into
> kernel build directory. However after this the following message is
> displayed:
> 
> 
> Using /home/user/buildroot-2020.02.8/output/build/linux-5.4.78/.config 
> as base
> #
> # merged configuration written to
> /home/user/buildroot-2020.02.8/output/build/linux-5.4.78/.config
> (needs make)
> #
> scripts/kconfig/conf  --olddefconfig Kconfig
> #

It looks as if you have a configuration fragment file configured which 
is big enough to overwrite everything. Check 
BR2_LINUX_KERNEL_CONFIG_FRAGMENT_FILES directly below the kernel 
configuration file and the content of the file.

> And then my custom configuration is overwritten and rt-patch config
> variables are not present anymore in actual kernel .config file.
> 
> I also tried with BR2_LINUX_KERNEL_PATCH variable, but the result is 
> the same.

I do not think this is patch related; you still should be able to 
configure RT settings when you execute 'make nconfig'.

> May you please help me? I've used BR2_GLOBAL_PATCH_DIR variable to
> apply other kernel patches since now without any problems.

Kind regards,
Andreas

> Thanks, Matteo