1 #ifndef _LINUX_SCATTERLIST_H 2 #define _LINUX_SCATTERLIST_H 3 4 #include <asm/scatterlist.h> 5 #include <linux/mm.h> 6 #include <linux/string.h> 7 8 static inline void sg_set_buf(struct scatterlist *sg, const void *buf, 9 unsigned int buflen) 10 { 11 sg->page = virt_to_page(buf); 12 sg->offset = offset_in_page(buf); 13 sg->length = buflen; 14 } 15 16 static inline void sg_init_one(struct scatterlist *sg, const void *buf, 17 unsigned int buflen) 18 { 19 memset(sg, 0, sizeof(*sg)); 20 sg_set_buf(sg, buf, buflen); 21 } 22 23 /* 24 * We overload the LSB of the page pointer to indicate whether it's 25 * a valid sg entry, or whether it points to the start of a new scatterlist. 26 * Those low bits are there for everyone! (thanks mason :-) 27 */ 28 #define sg_is_chain(sg) ((unsigned long) (sg)->page & 0x01) 29 #define sg_chain_ptr(sg) \ 30 ((struct scatterlist *) ((unsigned long) (sg)->page & ~0x01)) 31 32 /** 33 * sg_next - return the next scatterlist entry in a list 34 * @sg: The current sg entry 35 * 36 * Usually the next entry will be @sg@ + 1, but if this sg element is part 37 * of a chained scatterlist, it could jump to the start of a new 38 * scatterlist array. 39 * 40 * Note that the caller must ensure that there are further entries after 41 * the current entry, this function will NOT return NULL for an end-of-list. 42 * 43 */ 44 static inline struct scatterlist *sg_next(struct scatterlist *sg) 45 { 46 sg++; 47 48 if (unlikely(sg_is_chain(sg))) 49 sg = sg_chain_ptr(sg); 50 51 return sg; 52 } 53 54 /* 55 * Loop over each sg element, following the pointer to a new list if necessary 56 */ 57 #define for_each_sg(sglist, sg, nr, __i) \ 58 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg)) 59 60 /** 61 * sg_last - return the last scatterlist entry in a list 62 * @sgl: First entry in the scatterlist 63 * @nents: Number of entries in the scatterlist 64 * 65 * Should only be used casually, it (currently) scan the entire list 66 * to get the last entry. 67 * 68 * Note that the @sgl@ pointer passed in need not be the first one, 69 * the important bit is that @nents@ denotes the number of entries that 70 * exist from @sgl@. 71 * 72 */ 73 static inline struct scatterlist *sg_last(struct scatterlist *sgl, 74 unsigned int nents) 75 { 76 #ifndef ARCH_HAS_SG_CHAIN 77 struct scatterlist *ret = &sgl[nents - 1]; 78 #else 79 struct scatterlist *sg, *ret = NULL; 80 int i; 81 82 for_each_sg(sgl, sg, nents, i) 83 ret = sg; 84 85 #endif 86 return ret; 87 } 88 89 /** 90 * sg_chain - Chain two sglists together 91 * @prv: First scatterlist 92 * @prv_nents: Number of entries in prv 93 * @sgl: Second scatterlist 94 * 95 * Links @prv@ and @sgl@ together, to form a longer scatterlist. 96 * 97 */ 98 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, 99 struct scatterlist *sgl) 100 { 101 #ifndef ARCH_HAS_SG_CHAIN 102 BUG(); 103 #endif 104 prv[prv_nents - 1].page = (struct page *) ((unsigned long) sgl | 0x01); 105 } 106 107 #endif /* _LINUX_SCATTERLIST_H */ 108