Messages in this thread Patch in this message | | | From | Jens Axboe <> | Subject | [PATCH 7/10] i386 sg: add support for chaining scatterlists | Date | Wed, 16 May 2007 10:31:37 +0200 |
| |
The core of the patch - allow the last sg element in a scatterlist table to point to the start of a new table. This adds a pointer to the sglist structure, and defines sg_chain_ptr() which the generic code can use to look it up.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com> --- include/asm-i386/scatterlist.h | 4 ++++ include/linux/scatterlist.h | 37 ++++++++++++++++++++++++++++++++++--- 2 files changed, 38 insertions(+), 3 deletions(-)
diff --git a/include/asm-i386/scatterlist.h b/include/asm-i386/scatterlist.h index d7e45a8..794b68c 100644 --- a/include/asm-i386/scatterlist.h +++ b/include/asm-i386/scatterlist.h @@ -8,8 +8,11 @@ struct scatterlist { unsigned int offset; dma_addr_t dma_address; unsigned int length; + struct scatterlist *next; }; +#define ARCH_HAS_SG_CHAIN + /* These macros should be used after a pci_map_sg call has been done * to get bus addresses of each of the SG entries and their lengths. * You should only work with the number of sg entries pci_map_sg @@ -17,6 +20,7 @@ struct scatterlist { */ #define sg_dma_address(sg) ((sg)->dma_address) #define sg_dma_len(sg) ((sg)->length) +#define sg_chain_ptr(sg) ((sg)->next) #define ISA_DMA_THRESHOLD (0x00ffffff) diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index c5bffde..e3fc307 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -20,13 +20,44 @@ static inline void sg_init_one(struct scatterlist *sg, const void *buf, sg_set_buf(sg, buf, buflen); } -#define sg_next(sg) ((sg) + 1) -#define sg_last(sg, nents) (&(sg[nents - 1])) - /* * Loop over each sg element, following the pointer to a new list if necessary */ #define for_each_sg(sglist, sg, nr, __i) \ for (__i = 0, sg = (sglist); __i < nr; __i++, sg = sg_next(sg)) +#ifdef ARCH_HAS_SG_CHAIN +#define sg_next(sg) (sg_chain_ptr((sg)) ? : (sg) + 1) +/* + * Chain previous sglist to this one + */ +static inline void sg_chain(struct scatterlist *prv, unsigned int nents, + struct scatterlist *sgl) +{ + sg_chain_ptr(&prv[nents - 1]) = sgl; +} + +/* + * We could improve this by passing in the maximum size of an sglist, so + * we could jump directly to the last table. That would eliminate this + * (potentially) lengthy scan. + */ +static inline struct scatterlist *sg_last(struct scatterlist *sgl, + unsigned int nents) +{ + struct scatterlist *sg, *ret = NULL; + int i; + + for_each_sg(sgl, sg, nents, i) + ret = sg; + + return ret; +} +#else +#define sg_next(sg) ((sg) + 1) +#define sg_chain(prv, nents, sgl) BUG() +#define sg_chain_ptr(sg) NULL +#define sg_last(sg, nents) (&(sg[nents - 1])) +#endif + #endif /* _LINUX_SCATTERLIST_H */ -- 1.5.2.rc1 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |