On Thu, Jul 09, 2020 at 08:28:45PM -0700, John Stultz wrote: > On Thu, Jul 2, 2020 at 7:18 AM Will Deacon <will@xxxxxxxxxx> 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
