On 11/01/17 13:41, Nikita Yushchenko wrote: >> Yes, I think that ought to work, although the __iommu_setup_dma_ops() >> call will still want a real size reflecting the default mask > > I see iommu_dma_ops do not define set_dma_mask. > > So what if setup was done for size reflecting one mask and then driver > changes mask? Will things still operate correctly? We've overridden dma_set_mask() at the function level, so it should always apply regardless. Besides, none of the arm64 ops implement .set_dma_mask anyway, so we could possibly drop the references to it altogether. Conversely, I suppose we could just implement said callback for swiotlb_dma_ops and iommu_dma_ops with the parent_dma_mask-checking function and drop the HAVE_ARCH_DMA_SET_MASK override instead. I'm not sure which approach is preferable - the latter seems arguably cleaner in isolation, but would also be less consistent with how the coherent mask has to be handled. Ho hum. Robin.
