[Buildroot] Please help me on kernel configuration with rt-patch applied
Andreas Ziegler
br015 at umbiko.net
Mon Oct 25 09:11:28 UTC 2021
Hi Matteo,
On 2021-10-25 07:22, Pampolini Matteo wrote:
> Hello Andreas,
>
> many thanks for your answer and sorry for the delay of mine, during
> the weekend I did not have the chance to work on this issue.
>
> Anyway, I checked BR2_LINUX_KERNEL_CONFIG_FRAGMENT_FILES variable in
> my Buildroot configuration file and is empty, my approach
> for kernel patching always worked in other cases, what am I doing wrong
> now?
Sorry, my mistake, you get the 'merged configuration' message also on
builds without configuration fragment file.
I use PREEMPT_RT myself, usually in BR2_LINUX_KERNEL_PATCH, and seldom
had issues.
Could you check if you can configure PREEMPT_RT features manually after
initial creation of the kernel directory?
$ rm -fr output/build/linux-5.4.78
$ make linux-nconfig
On the off chance, which architecture are you building for? These
architectures are supported by PREEMPT_RT:
$ cd build/linux-5.4.155
$ fg ARCH_SUPPORTS_RT
./arch/arm/Kconfig: select ARCH_SUPPORTS_RT
./arch/arm64/Kconfig: select ARCH_SUPPORTS_RT
./arch/powerpc/Kconfig: select ARCH_SUPPORTS_RT
./arch/x86/Kconfig: select ARCH_SUPPORTS_RT
Also, CONFIG_EXPERT must be selected to be able to configure a fully
preemptable kernel.
Kind regards,
Andreas
> Regards, Matteo
>
>
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> -----Messaggio originale-----
> Da: Andreas Ziegler [mailto:br015 at umbiko.net]
> Inviato: venerdì 22 ottobre 2021 18:27
> A: Pampolini Matteo <matteo.pampolini at leonardocompany.com>
> Oggetto: Re: Please help me on kernel configuration with rt-patch
> applied
>
> 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
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