On Wed, Feb 26, 2025 at 10:57:00AM -0800, Nicolin Chen wrote:

OK, I see. But we are also changing the behavior for the
!CONFIG_IOMMU_DMA configuration, in which case all other iommu
functions seem to return -ENODEV. And I assume we would need a
justification for such a change?

Perhaps, this can be explicit, just to keep the consistency:
	/* NOP if IOMMU driver reports SW_MSI reserved regions */
	return IS_ENABLED(CONFIG_IOMMU_DMA) ? 0 : -ENODEV;

Hurm, I donno, if we don't have a IRQ driver that supports it then it
doesn't matter that IOMMU_DMA is off either because there is nothing
that would call into IOMMU_DMA in the first place.

Success still seems like the right answer on such a weirdo kconfig.

Jason