On Thu, Jul 09, 2020 at 08:28:45PM -0700, John Stultz wrote:
> On Thu, Jul 2, 2020 at 7:18 AM Will Deacon <w...@kernel.org> wrote:
> > On Thu, Jun 25, 2020 at 12:10:39AM +0000, John Stultz wrote:
> > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> > > index b510f67dfa49..714893535dd2 100644
> > > --- a/drivers/iommu/Kconfig
> > > +++ b/drivers/iommu/Kconfig
> > > @@ -381,6 +381,7 @@ config SPAPR_TCE_IOMMU
> > > config ARM_SMMU
> > > tristate "ARM Ltd. System MMU (SMMU) Support"
> > > depends on (ARM64 || ARM || (COMPILE_TEST && !GENERIC_ATOMIC64)) &&
> > > MMU
> > > + depends on QCOM_SCM || !QCOM_SCM #if QCOM_SCM=m this can't be =y
> > > select IOMMU_API
> > > select IOMMU_IO_PGTABLE_LPAE
> > > select ARM_DMA_USE_IOMMU if ARM
> >
> > This looks like a giant hack. Is there another way to handle this?
>
> Sorry for the slow response here.
>
> So, I agree the syntax looks strange (requiring a comment obviously
> isn't a good sign), but it's a fairly common way to ensure drivers
> don't get built in if they optionally depend on another driver that
> can be built as a module.
> See "RFKILL || !RFKILL", "EXTCON || !EXTCON", or "USB_GADGET ||
> !USB_GADGET" in various Kconfig files.
>
> I'm open to using a different method, and in a different thread you
> suggested using something like symbol_get(). I need to look into it
> more, but that approach looks even more messy and prone to runtime
> failures. Blocking the unwanted case at build time seems a bit cleaner
> to me, even if the syntax is odd.
Maybe just split it out then, so that the ARM_SMMU entry doesn't have this,
as that driver _really_ doesn't care about SoC details like this. In other
words, add a new entry along the lines of:
config ARM_SMMU_QCOM_IMPL
default y
#if QCOM_SCM=m this can't be =y
depends on ARM_SMMU & (QCOM_SCM || !QCOM_SCM)
and then have arm-smmu.h provide a static inline qcom_smmu_impl_init()
which returns -ENODEV if CONFIG_ARM_SMMU_QCOM_IMPL=n and hack the Makefile
so that we don't bother to compile arm-smmu-qcom.o in that case.
Would that work?
Will
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