Re: [PATCH] dma-remap: fix dma_common_find_pages() page lookup for offsets

[Andrei-Edward Popa]

Hi Christoph, Marek, Robin,

Thanks for the detailed explanations, that clarified things a lot.

I now understand that dma_mmap_attrs() expects cpu_addr to be the exact
pointer returned by dma_alloc_attrs(), and that subdividing an allocation
(e.g. via gen_pool) requires the driver to keep track of offsets and
adjust the mmap parameters accordingly before calling into the DMA API.

My patch was effectively trying to make dma_common_find_pages() accept
offset cpu_addr values implicitly, which would change the DMA API
semantics and mask driver bugs rather than fixing them in the driver
itself.

Given this, I agree that the correct fix is in the driver using the API,
not in dma-remap, and I’ll drop this patch.

Thanks again for taking the time to explain the intended usage and
constraints of the DMA mmap helpers.

Best regards,
Andrei