From 10c95ed9aa2970e05fedb4ac8b3ce1b934dab17b Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Fri, 7 Aug 2015 18:15:11 +0200 Subject: scatterlist: allow limited chaining without ARCH_HAS_SG_CHAIN There are a couple of uses of struct scatterlist that never go to the dma_map_sg() helper and thus don't care about ARCH_HAS_SG_CHAIN which indicates that we can map chained S/G list. The most important one is the crypto code, which currently has to open code a few helpers to always allow chaining. This patch removes a few #ifdef ARCH_HAS_SG_CHAIN statements so that we can switch the crypto code to these common helpers. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- include/linux/scatterlist.h | 4 ---- 1 file changed, 4 deletions(-) (limited to 'include/linux') diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 9b1ef0c820a7..698e906ca730 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -161,10 +161,6 @@ static inline void sg_set_buf(struct scatterlist *sg, const void *buf, static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, struct scatterlist *sgl) { -#ifndef CONFIG_ARCH_HAS_SG_CHAIN - BUG(); -#endif - /* * offset and length are unused for chain entry. Clear them. */ -- cgit v1.2.3 From f8bcbe62acd0e1ce9004b83e98a4af87ae385dcf Mon Sep 17 00:00:00 2001 From: Robert Jarzmik Date: Sat, 8 Aug 2015 10:44:10 +0200 Subject: lib: scatterlist: add sg splitting function Sometimes a scatter-gather has to be split into several chunks, or sub scatter lists. This happens for example if a scatter list will be handled by multiple DMA channels, each one filling a part of it. A concrete example comes with the media V4L2 API, where the scatter list is allocated from userspace to hold an image, regardless of the knowledge of how many DMAs will fill it : - in a simple RGB565 case, one DMA will pump data from the camera ISP to memory - in the trickier YUV422 case, 3 DMAs will pump data from the camera ISP pipes, one for pipe Y, one for pipe U and one for pipe V For these cases, it is necessary to split the original scatter list into multiple scatter lists, which is the purpose of this patch. The guarantees that are required for this patch are : - the intersection of spans of any couple of resulting scatter lists is empty. - the union of spans of all resulting scatter lists is a subrange of the span of the original scatter list. - streaming DMA API operations (mapping, unmapping) should not happen both on both the resulting and the original scatter list. It's either the first or the later ones. - the caller is reponsible to call kfree() on the resulting scatterlists. Signed-off-by: Robert Jarzmik Signed-off-by: Jens Axboe --- include/linux/scatterlist.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux') diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 698e906ca730..556ec1ea2574 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -247,6 +247,11 @@ struct scatterlist *sg_next(struct scatterlist *); struct scatterlist *sg_last(struct scatterlist *s, unsigned int); void sg_init_table(struct scatterlist *, unsigned int); void sg_init_one(struct scatterlist *, const void *, unsigned int); +int sg_split(struct scatterlist *in, const int in_mapped_nents, + const off_t skip, const int nb_splits, + const size_t *split_sizes, + struct scatterlist **out, int *out_mapped_nents, + gfp_t gfp_mask); typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t); typedef void (sg_free_fn)(struct scatterlist *, unsigned int); -- cgit v1.2.3