On Thu, Nov 22, 2018 at 06:05:26PM +0000, Russell King - ARM Linux wrote:

An alternative idea would be to migrate away from the
dma_map_single() and dma_map_page() interfaces that return a
dma_addr_t, and instead have them return an error code or zero
on success.

See here for a proposal:

https://lists.linuxfoundation.org/pipermail/iommu/2018-November/030912.html

That is just the attr variants, but that would be a start.  Dave didn't
particularly like it, though.

note the simpler unmap API, which inherently guarantees that the
parameters to the map could be carried over to the unmap - without
our many driver authors having to think about it.

The problem is that we can often derive some or all parameters from
field already inherent in the upper layer or hardware interface.  So
for these cases your version would bloat the required data structures.