scatterlist: add sg_alloc_table_from_pages function
This patch adds a new constructor for an sg table. The table is constructed from an array of struct pages. All contiguous chunks of the pages are merged into a single sg nodes. A user may provide an offset and a size of a buffer if the buffer is not page-aligned. The function is dedicated for DMABUF exporters which often perform conversion from an page array to a scatterlist. Moreover the scatterlist should be squashed in order to save memory and to speed-up the process of DMA mapping using dma_map_sg. The code is based on the patch 'v4l: vb2-dma-contig: add support for scatterlist in userptr mode' and hints from Laurent Pinchart. Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> CC: Andrew Morton <akpm@linux-foundation.org>
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