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SubjectRe: [RFC PATCH] drivers: use 'depends on MFD_SYSCON' instead of 'select MFD_SYSCON'
2018-02-26 17:43 GMT+09:00 Arnd Bergmann <>:
> On Sat, Feb 24, 2018 at 3:50 PM, Masahiro Yamada
> <> wrote:
>> As Documentation/kbuild/kconfig-language.txt notes, 'select' should be
>> used with care - it forces a lower limit of another symbol, ignoring
>> the dependency.
>> MFD_SYSCON depends on HAS_IOMEM, but several drivers with COMPILE_TEST
>> select it.
>> This causes unmet dependencies for architecture without HAS_IOMEM.
>> $ make ARCH=score randconfig
>> scripts/kconfig/conf --randconfig Kconfig
>> KCONFIG_SEED=0x27C47F43
>> selects MFD_SYSCON which has unmet direct dependencies (HAS_IOMEM)
>> Use 'depends on' to observe the dependency.
>> This commit was created by the following command:
>> $ find drivers -name 'Kconfig*' | xargs sed -i -e \
>> 's/select MFD_SYSCON$/depends on MFD_SYSCON/'
>> Then, COMMON_CLK_NXP and S3C2410_WATCHDOG were fixed up manually.
>> Also, make MFD_SYSCON 'default y' because some defconfig files may
>> rely on someone select's MFD_SYSCON.
>> Signed-off-by: Masahiro Yamada <>
>> ---
>> If you have a better idea to fix 'unmet dependencies',
>> please suggest.
> Changing 'select MFD_SYSCON' to 'depends on' will definitely break lots
> of defconfig configurations, I'd rather not do that.

Could you explain why?

I set 'default y' for MFD_SYSCON.

Would it still break defconfig configurations?

> Only score, tile and um have some configurations that select 'NO_IOMEM'.
> Score is getting removed now, tile might get removed later (we could make
> PCI mandatory in the meantime to avoid that configuration), and I think for
> um, we already have a workaround for the NO_IOMEM dependencies
> (I forget the details).

I do not think this is a stable solution.

Or, do you mean to remove NO_IOMEM and HAS_IOMEM completely?

Best Regards
Masahiro Yamada

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