[RFC PATCH] drivers: use 'depends on MFD_SYSCON' instead of 'select MFD_SYSCON'

On Sat, Feb 24, 2018 at 3:50 PM, Masahiro Yamada
[off-list ref] 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
  warning: (HWSPINLOCK_QCOM && AHCI_MTK && STMMAC_PLATFORM && ...)
  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 <redacted>
---

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.

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).

        Arnd