diff options
Diffstat (limited to 'include/linux/scatterlist.h')
| -rw-r--r-- | include/linux/scatterlist.h | 266 |
1 files changed, 263 insertions, 3 deletions
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 4efbd9c445f..32326c293d7 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -1,23 +1,283 @@ #ifndef _LINUX_SCATTERLIST_H #define _LINUX_SCATTERLIST_H +#include <asm/types.h> #include <asm/scatterlist.h> #include <linux/mm.h> #include <linux/string.h> +#include <asm/io.h> +/* + * Notes on SG table design. + * + * Architectures must provide an unsigned long page_link field in the + * scatterlist struct. We use that to place the page pointer AND encode + * information about the sg table as well. The two lower bits are reserved + * for this information. + * + * If bit 0 is set, then the page_link contains a pointer to the next sg + * table list. Otherwise the next entry is at sg + 1. + * + * If bit 1 is set, then this sg entry is the last element in a list. + * + * See sg_next(). + * + */ + +#define SG_MAGIC 0x87654321 + +/** + * sg_assign_page - Assign a given page to an SG entry + * @sg: SG entry + * @page: The page + * + * Description: + * Assign page to sg entry. Also see sg_set_page(), the most commonly used + * variant. + * + **/ +static inline void sg_assign_page(struct scatterlist *sg, struct page *page) +{ + unsigned long page_link = sg->page_link & 0x3; + + /* + * In order for the low bit stealing approach to work, pages + * must be aligned at a 32-bit boundary as a minimum. + */ + BUG_ON((unsigned long) page & 0x03); +#ifdef CONFIG_DEBUG_SG + BUG_ON(sg->sg_magic != SG_MAGIC); +#endif + sg->page_link = page_link | (unsigned long) page; +} + +/** + * sg_set_page - Set sg entry to point at given page + * @sg: SG entry + * @page: The page + * @len: Length of data + * @offset: Offset into page + * + * Description: + * Use this function to set an sg entry pointing at a page, never assign + * the page directly. We encode sg table information in the lower bits + * of the page pointer. See sg_page() for looking up the page belonging + * to an sg entry. + * + **/ +static inline void sg_set_page(struct scatterlist *sg, struct page *page, + unsigned int len, unsigned int offset) +{ + sg_assign_page(sg, page); + sg->offset = offset; + sg->length = len; +} + +#define sg_page(sg) ((struct page *) ((sg)->page_link & ~0x3)) + +/** + * sg_set_buf - Set sg entry to point at given data + * @sg: SG entry + * @buf: Data + * @buflen: Data length + * + **/ static inline void sg_set_buf(struct scatterlist *sg, const void *buf, unsigned int buflen) { - sg->page = virt_to_page(buf); - sg->offset = offset_in_page(buf); - sg->length = buflen; + sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf)); +} + +/* + * We overload the LSB of the page pointer to indicate whether it's + * a valid sg entry, or whether it points to the start of a new scatterlist. + * Those low bits are there for everyone! (thanks mason :-) + */ +#define sg_is_chain(sg) ((sg)->page_link & 0x01) +#define sg_is_last(sg) ((sg)->page_link & 0x02) +#define sg_chain_ptr(sg) \ + ((struct scatterlist *) ((sg)->page_link & ~0x03)) + +/** + * sg_next - return the next scatterlist entry in a list + * @sg: The current sg entry + * + * Description: + * Usually the next entry will be @sg@ + 1, but if this sg element is part + * of a chained scatterlist, it could jump to the start of a new + * scatterlist array. + * + **/ +static inline struct scatterlist *sg_next(struct scatterlist *sg) +{ +#ifdef CONFIG_DEBUG_SG + BUG_ON(sg->sg_magic != SG_MAGIC); +#endif + if (sg_is_last(sg)) + return NULL; + + sg++; + if (unlikely(sg_is_chain(sg))) + sg = sg_chain_ptr(sg); + + return sg; +} + +/* + * 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)) + +/** + * sg_last - return the last scatterlist entry in a list + * @sgl: First entry in the scatterlist + * @nents: Number of entries in the scatterlist + * + * Description: + * Should only be used casually, it (currently) scan the entire list + * to get the last entry. + * + * Note that the @sgl@ pointer passed in need not be the first one, + * the important bit is that @nents@ denotes the number of entries that + * exist from @sgl@. + * + **/ +static inline struct scatterlist *sg_last(struct scatterlist *sgl, + unsigned int nents) +{ +#ifndef ARCH_HAS_SG_CHAIN + struct scatterlist *ret = &sgl[nents - 1]; +#else + struct scatterlist *sg, *ret = NULL; + unsigned int i; + + for_each_sg(sgl, sg, nents, i) + ret = sg; + +#endif +#ifdef CONFIG_DEBUG_SG + BUG_ON(sgl[0].sg_magic != SG_MAGIC); + BUG_ON(!sg_is_last(ret)); +#endif + return ret; +} + +/** + * sg_chain - Chain two sglists together + * @prv: First scatterlist + * @prv_nents: Number of entries in prv + * @sgl: Second scatterlist + * + * Description: + * Links @prv@ and @sgl@ together, to form a longer scatterlist. + * + **/ +static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, + struct scatterlist *sgl) +{ +#ifndef ARCH_HAS_SG_CHAIN + BUG(); +#endif + /* + * Set lowest bit to indicate a link pointer, and make sure to clear + * the termination bit if it happens to be set. + */ + prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02; +} + +/** + * sg_mark_end - Mark the end of the scatterlist + * @sgl: Scatterlist + * @nents: Number of entries in sgl + * + * Description: + * Marks the last entry as the termination point for sg_next() + * + **/ +static inline void sg_mark_end(struct scatterlist *sgl, unsigned int nents) +{ + sgl[nents - 1].page_link = 0x02; +} + +static inline void __sg_mark_end(struct scatterlist *sg) +{ + sg->page_link |= 0x02; } +/** + * sg_init_one - Initialize a single entry sg list + * @sg: SG entry + * @buf: Virtual address for IO + * @buflen: IO length + * + * Notes: + * This should not be used on a single entry that is part of a larger + * table. Use sg_init_table() for that. + * + **/ static inline void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen) { memset(sg, 0, sizeof(*sg)); +#ifdef CONFIG_DEBUG_SG + sg->sg_magic = SG_MAGIC; +#endif + sg_mark_end(sg, 1); sg_set_buf(sg, buf, buflen); } +/** + * sg_init_table - Initialize SG table + * @sgl: The SG table + * @nents: Number of entries in table + * + * Notes: + * If this is part of a chained sg table, sg_mark_end() should be + * used only on the last table part. + * + **/ +static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents) +{ + memset(sgl, 0, sizeof(*sgl) * nents); + sg_mark_end(sgl, nents); +#ifdef CONFIG_DEBUG_SG + { + unsigned int i; + for (i = 0; i < nents; i++) + sgl[i].sg_magic = SG_MAGIC; + } +#endif +} + +/** + * sg_phys - Return physical address of an sg entry + * @sg: SG entry + * + * Description: + * This calls page_to_phys() on the page in this sg entry, and adds the + * sg offset. The caller must know that it is legal to call page_to_phys() + * on the sg page. + * + **/ +static inline dma_addr_t sg_phys(struct scatterlist *sg) +{ + return page_to_phys(sg_page(sg)) + sg->offset; +} + +/** + * sg_virt - Return virtual address of an sg entry + * @sg: SG entry + * + * Description: + * This calls page_address() on the page in this sg entry, and adds the + * sg offset. The caller must know that the sg page has a valid virtual + * mapping. + * + **/ +static inline void *sg_virt(struct scatterlist *sg) +{ + return page_address(sg_page(sg)) + sg->offset; +} + #endif /* _LINUX_SCATTERLIST_H */ |