21.08.2020 03:28, Robin Murphy пишет:
...

quoted

Will a returned NULL tell to IOMMU core that implicit domain shouldn't
be used? Is it possible to leave this driver as-is?

The aim of this patch was just to make the conversion without functional
changes wherever possible, i.e. maintain an equivalent to the existing
ARM behaviour of allocating its own implicit domains for everything. It
doesn't represent any judgement of whether that was ever appropriate for
this driver in the first place ;)

Hopefully my other reply already covered the degree of control drivers
can have with proper default domains, but do shout if anything wasn't
clear.

Thank you for the detailed comments! I wasn't watching closely all the
recent iommu/ changes and yours clarification is very helpful!

My current understanding is that the GART driver will need to support
the IOMMU_DOMAIN_IDENTITY and set def_domain_type to
IOMMU_DOMAIN_IDENTITY for all devices.

Meanwhile, today's upstream drivers don't use GART, hence this patch
should be okay. Although, it's a bit unlikely that the IOMMU_DOMAIN_DMA
type will ever be useful for the GART, and thus, I'm still thinking that
will be a bit nicer to keep GART driver as-is for now.

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