On Thu, Aug 20, 2020 at 6:52 PM Christoph Hellwig <hch@xxxxxx> wrote: > > On Thu, Aug 20, 2020 at 12:24:31PM +0200, Tomasz Figa wrote: > > > Of course this still uses the scatterlist structure with its annoying > > > mix of input and output parametes, so I'd rather not expose it as > > > an official API at the DMA layer. > > > > The problem with the above open coded approach is that it requires > > explicit handling of the non-IOMMU and IOMMU cases and this is exactly > > what we don't want to have in vb2 and what was actually the job of the > > DMA API to hide. Is the plan to actually move the IOMMU handling out > > of the DMA API? > > > > Do you think we could instead turn it into a dma_alloc_noncoherent() > > helper, which has similar semantics as dma_alloc_attrs() and handles > > the various corner cases (e.g. invalidate_kernel_vmap_range and > > flush_kernel_vmap_range) to achieve the desired functionality without > > delegating the "hell", as you called it, to the users? > > Yes, I guess I could do something in that direction. At least for > dma-iommu, which thanks to Robin should be all you'll need in the > foreseeable future. That would be really great. Let me know if we can help by testing with V4L2/vb2 or in any other way. Best regards, Tomasz
