On 4/30/2018 9:54 AM, Robin Murphy wrote: > For dma_map_sg(), DMA API implementations are free to merge consecutive > segments into a single DMA mapping if conditions are suitable, thus the > resulting DMA addresses which drm_prime_sg_to_page_addr_arrays() > iterates over may be packed into fewer entries than sgt->nents implies. > > The current implementation does not account for this, meaning that its > callers either have to reject the 0 < count < nents case or risk getting > bogus DMA addresses beyond the first segment. Fortunately this is quite > easy to handle without having to rejig structures to also store the > mapped count, since the total DMA length should still be equal to the > total buffer length. All we need is a second scatterlist cursor to > iterate through the DMA addresses independently of the page addresses. > > Reviewed-by: Christian König <christian.koenig at amd.com> > Signed-off-by: Robin Murphy <robin.murphy at arm.com> > --- Much better Tested-by: Sinan Kaya <okaya at codeauora.org> for the first two patches. (1/3 and 2/3) -- Sinan Kaya Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
