diff options
Diffstat (limited to 'include/linux/scatterlist.h')
| -rw-r--r-- | include/linux/scatterlist.h | 232 |
1 files changed, 203 insertions, 29 deletions
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 2dc7464cce52..259735044148 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -1,23 +1,91 @@ #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> -static inline void sg_set_buf(struct scatterlist *sg, const void *buf, - unsigned int buflen) +/* + * 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) { - sg->page = virt_to_page(buf); - sg->offset = offset_in_page(buf); - sg->length = buflen; + 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; } -static inline void sg_init_one(struct scatterlist *sg, const void *buf, - unsigned int buflen) +/** + * 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) { - memset(sg, 0, sizeof(*sg)); - sg_set_buf(sg, buf, buflen); + 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_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf)); } /* @@ -25,26 +93,30 @@ static inline void sg_init_one(struct scatterlist *sg, const void *buf, * 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) ((unsigned long) (sg)->page & 0x01) +#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 *) ((unsigned long) (sg)->page & ~0x01)) + ((struct scatterlist *) ((sg)->page_link & ~0x03)) /** * sg_next - return the next scatterlist entry in a list * @sg: The current sg entry * - * 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. - * - * Note that the caller must ensure that there are further entries after - * the current entry, this function will NOT return NULL for an end-of-list. + * 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) { - 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); @@ -62,14 +134,15 @@ static inline struct scatterlist *sg_next(struct scatterlist *sg) * @sgl: First entry in the scatterlist * @nents: Number of entries in the scatterlist * - * Should only be used casually, it (currently) scan the entire list - * to get the last entry. + * 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@. + * 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) { @@ -77,12 +150,16 @@ static inline struct scatterlist *sg_last(struct scatterlist *sgl, struct scatterlist *ret = &sgl[nents - 1]; #else struct scatterlist *sg, *ret = NULL; - int i; + 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; } @@ -92,16 +169,113 @@ static inline struct scatterlist *sg_last(struct scatterlist *sgl, * @prv_nents: Number of entries in prv * @sgl: Second scatterlist * - * Links @prv@ and @sgl@ together, to form a longer 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 - prv[prv_nents - 1].page = (struct page *) ((unsigned long) sgl | 0x01); + /* + * 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 + * @sg: SG entryScatterlist + * + * Description: + * Marks the passed in sg entry as the termination point for the sg + * table. A call to sg_next() on this entry will return NULL. + * + **/ +static inline void sg_mark_end(struct scatterlist *sg) +{ +#ifdef CONFIG_DEBUG_SG + BUG_ON(sg->sg_magic != SG_MAGIC); +#endif + /* + * Set termination bit, clear potential chain bit + */ + sg->page_link |= 0x02; + sg->page_link &= ~0x01; +} + +/** + * 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); +#ifdef CONFIG_DEBUG_SG + { + unsigned int i; + for (i = 0; i < nents; i++) + sgl[i].sg_magic = SG_MAGIC; + } +#endif + sg_mark_end(&sgl[nents - 1]); +} + +/** + * 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) +{ + sg_init_table(sg, 1); + sg_set_buf(sg, buf, buflen); +} + +/** + * 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 */ |