[PATCH] powerpc: iommu: fix build when neither PCI or IBMVIO is set

[Michael Ellerman]

Randy Dunlap <rdunlap at infradead.org> writes:
> When neither CONFIG_PCI nor CONFIG_IBMVIO is enabled:
>
> ../arch/powerpc/kernel/iommu.c:178:30: error: 'fail_iommu_bus_notifier' defined but not used [-Werror=unused-variable]
>   178 | static struct notifier_block fail_iommu_bus_notifier = {
>
> If only that struct is bounded by 2 #if defined() phrases (PCI && IBMVIO):
>
> ../arch/powerpc/kernel/iommu.c:162:12: error: 'fail_iommu_bus_notify' defined but not used [-Werror=unused-function]
>   162 | static int fail_iommu_bus_notify(struct notifier_block *nb,
>
> If that function is also guarded by 2 #if defined() phrases:
>
> In file included from ../include/linux/dma-mapping.h:7,
>                  from ../arch/powerpc/kernel/iommu.c:19:
> ../include/linux/device.h:131:26: error: 'dev_attr_fail_iommu' defined but not used [-Werror=unused-variable]
>   131 |  struct device_attribute dev_attr_##_name = __ATTR_RW(_name)
> ../arch/powerpc/kernel/iommu.c:160:8: note: in expansion of macro 'DEVICE_ATTR_RW'
>   160 | static DEVICE_ATTR_RW(fail_iommu);
>
> and the snowball continues to grow.
> Next I got this one:
>
> ../arch/powerpc/kernel/iommu.c: In function 'iommu_range_alloc':
> ../arch/powerpc/kernel/iommu.c:234:6: error: implicit declaration of function 'should_fail_iommu'; did you mean 'should_failslab'? [-Werror=implicit-function-declaration]
>   234 |  if (should_fail_iommu(dev))
>
> and
>
> ../arch/powerpc/kernel/iommu.c: In function 'should_fail_iommu':
> ../arch/powerpc/kernel/iommu.c:122:50: error: 'fail_iommu' undeclared (first use in this function)
>   122 |  return dev->archdata.fail_iommu && should_fail(&fail_iommu, 1);
>
> So combine CONFIG_FAIL_IOMMU && (CONFIG_PCI || CONFIG_IBMVIO)
> to decide on building some of this code/data.

Couldn't we just make FAIL_IOMMU depend on PCI || IBMVIO?

cheers