On Wed, Jun 13, 2012 at 01:50:15PM +0200, Marek Szyprowski wrote:
This patch adds dma_get_sgtable() function which is required to let drivers to share the buffers allocated by DMA-mapping subsystem. Right now the driver gets a dma address of the allocated buffer and the kernel virtual mapping for it. If it wants to share it with other device (= map into its dma address space) it usually hacks around kernel virtual addresses to get pointers to pages or assumes that both devices share the DMA address space. Both solutions are just hacks for the special cases, which should be avoided in the final version of buffer sharing.
To solve this issue in a generic way, a new call to DMA mapping has been introduced - dma_get_sgtable(). It allocates a scatter-list which describes the allocated buffer and lets the driver(s) to use it with other device(s) by calling dma_map_sg() on it.
This patch provides a generic implementation based on virt_to_page() call. Architectures which require more sophisticated translation might provide their own get_sgtable() methods.
Signed-off-by: Marek Szyprowski m.szyprowski@samsung.com Reviewed-by: Kyungmin Park kyungmin.park@samsung.com
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch