Hello, On 7/17/2013 11:43 AM, Ricardo Ribalda Delgado wrote:
Hi Marek alloc_pages_exact returns pages of order 0, every single page is filled into buf->pages, that then is used by vb2_dma_sg_mmap(), that also expects order 0 pages (its loops increments in PAGE_SIZE). The code has been tested on real HW. Your concern is that that alloc_pages_exact splits the higher order pages? Do you want that videobuf2-dma-sg to have support for higher order pages?
Ah... My fault. I didn't notice that you recalculate req_pages at the begginning of each loop iteration, so the code is correct, buf->pages is filled correctly with order 0 pages. So now the only issue I see is the oversized sglist allocation (the size of sg list is computed for worst case, 0 order pages) and lack of the max segment size support. Sadly there are devices which can handle single sg chunk up to some predefined size (see dma_get_max_seg_size() function). For some reference code, please check __iommu_map_sg() and maybe __iommu_alloc_buffer() functions in arch/arm/mm/dma-mapping.c Best regards -- Marek Szyprowski Samsung R&D Institute Poland -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
