1 #ifndef _LINUX_SCATTERLIST_H 2 #define _LINUX_SCATTERLIST_H 3 4 #include <asm/types.h> 5 #include <asm/scatterlist.h> 6 #include <linux/mm.h> 7 #include <linux/string.h> 8 #include <asm/io.h> 9 10 struct sg_table { 11 struct scatterlist *sgl; /* the list */ 12 unsigned int nents; /* number of mapped entries */ 13 unsigned int orig_nents; /* original size of list */ 14 }; 15 16 /* 17 * Notes on SG table design. 18 * 19 * Architectures must provide an unsigned long page_link field in the 20 * scatterlist struct. We use that to place the page pointer AND encode 21 * information about the sg table as well. The two lower bits are reserved 22 * for this information. 23 * 24 * If bit 0 is set, then the page_link contains a pointer to the next sg 25 * table list. Otherwise the next entry is at sg + 1. 26 * 27 * If bit 1 is set, then this sg entry is the last element in a list. 28 * 29 * See sg_next(). 30 * 31 */ 32 33 #define SG_MAGIC 0x87654321 34 35 /* 36 * We overload the LSB of the page pointer to indicate whether it's 37 * a valid sg entry, or whether it points to the start of a new scatterlist. 38 * Those low bits are there for everyone! (thanks mason :-) 39 */ 40 #define sg_is_chain(sg) ((sg)->page_link & 0x01) 41 #define sg_is_last(sg) ((sg)->page_link & 0x02) 42 #define sg_chain_ptr(sg) \ 43 ((struct scatterlist *) ((sg)->page_link & ~0x03)) 44 45 /** 46 * sg_assign_page - Assign a given page to an SG entry 47 * @sg: SG entry 48 * @page: The page 49 * 50 * Description: 51 * Assign page to sg entry. Also see sg_set_page(), the most commonly used 52 * variant. 53 * 54 **/ 55 static inline void sg_assign_page(struct scatterlist *sg, struct page *page) 56 { 57 unsigned long page_link = sg->page_link & 0x3; 58 59 /* 60 * In order for the low bit stealing approach to work, pages 61 * must be aligned at a 32-bit boundary as a minimum. 62 */ 63 BUG_ON((unsigned long) page & 0x03); 64 #ifdef CONFIG_DEBUG_SG 65 BUG_ON(sg->sg_magic != SG_MAGIC); 66 BUG_ON(sg_is_chain(sg)); 67 #endif 68 sg->page_link = page_link | (unsigned long) page; 69 } 70 71 /** 72 * sg_set_page - Set sg entry to point at given page 73 * @sg: SG entry 74 * @page: The page 75 * @len: Length of data 76 * @offset: Offset into page 77 * 78 * Description: 79 * Use this function to set an sg entry pointing at a page, never assign 80 * the page directly. We encode sg table information in the lower bits 81 * of the page pointer. See sg_page() for looking up the page belonging 82 * to an sg entry. 83 * 84 **/ 85 static inline void sg_set_page(struct scatterlist *sg, struct page *page, 86 unsigned int len, unsigned int offset) 87 { 88 sg_assign_page(sg, page); 89 sg->offset = offset; 90 sg->length = len; 91 } 92 93 static inline struct page *sg_page(struct scatterlist *sg) 94 { 95 #ifdef CONFIG_DEBUG_SG 96 BUG_ON(sg->sg_magic != SG_MAGIC); 97 BUG_ON(sg_is_chain(sg)); 98 #endif 99 return (struct page *)((sg)->page_link & ~0x3); 100 } 101 102 /** 103 * sg_set_buf - Set sg entry to point at given data 104 * @sg: SG entry 105 * @buf: Data 106 * @buflen: Data length 107 * 108 **/ 109 static inline void sg_set_buf(struct scatterlist *sg, const void *buf, 110 unsigned int buflen) 111 { 112 sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf)); 113 } 114 115 /* 116 * Loop over each sg element, following the pointer to a new list if necessary 117 */ 118 #define for_each_sg(sglist, sg, nr, __i) \ 119 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg)) 120 121 /** 122 * sg_chain - Chain two sglists together 123 * @prv: First scatterlist 124 * @prv_nents: Number of entries in prv 125 * @sgl: Second scatterlist 126 * 127 * Description: 128 * Links @prv@ and @sgl@ together, to form a longer scatterlist. 129 * 130 **/ 131 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, 132 struct scatterlist *sgl) 133 { 134 #ifndef ARCH_HAS_SG_CHAIN 135 BUG(); 136 #endif 137 138 /* 139 * offset and length are unused for chain entry. Clear them. 140 */ 141 prv[prv_nents - 1].offset = 0; 142 prv[prv_nents - 1].length = 0; 143 144 /* 145 * Set lowest bit to indicate a link pointer, and make sure to clear 146 * the termination bit if it happens to be set. 147 */ 148 prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02; 149 } 150 151 /** 152 * sg_mark_end - Mark the end of the scatterlist 153 * @sg: SG entryScatterlist 154 * 155 * Description: 156 * Marks the passed in sg entry as the termination point for the sg 157 * table. A call to sg_next() on this entry will return NULL. 158 * 159 **/ 160 static inline void sg_mark_end(struct scatterlist *sg) 161 { 162 #ifdef CONFIG_DEBUG_SG 163 BUG_ON(sg->sg_magic != SG_MAGIC); 164 #endif 165 /* 166 * Set termination bit, clear potential chain bit 167 */ 168 sg->page_link |= 0x02; 169 sg->page_link &= ~0x01; 170 } 171 172 /** 173 * sg_phys - Return physical address of an sg entry 174 * @sg: SG entry 175 * 176 * Description: 177 * This calls page_to_phys() on the page in this sg entry, and adds the 178 * sg offset. The caller must know that it is legal to call page_to_phys() 179 * on the sg page. 180 * 181 **/ 182 static inline dma_addr_t sg_phys(struct scatterlist *sg) 183 { 184 return page_to_phys(sg_page(sg)) + sg->offset; 185 } 186 187 /** 188 * sg_virt - Return virtual address of an sg entry 189 * @sg: SG entry 190 * 191 * Description: 192 * This calls page_address() on the page in this sg entry, and adds the 193 * sg offset. The caller must know that the sg page has a valid virtual 194 * mapping. 195 * 196 **/ 197 static inline void *sg_virt(struct scatterlist *sg) 198 { 199 return page_address(sg_page(sg)) + sg->offset; 200 } 201 202 struct scatterlist *sg_next(struct scatterlist *); 203 struct scatterlist *sg_last(struct scatterlist *s, unsigned int); 204 void sg_init_table(struct scatterlist *, unsigned int); 205 void sg_init_one(struct scatterlist *, const void *, unsigned int); 206 207 typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t); 208 typedef void (sg_free_fn)(struct scatterlist *, unsigned int); 209 210 void __sg_free_table(struct sg_table *, unsigned int, sg_free_fn *); 211 void sg_free_table(struct sg_table *); 212 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, gfp_t, 213 sg_alloc_fn *); 214 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t); 215 216 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, 217 void *buf, size_t buflen); 218 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, 219 void *buf, size_t buflen); 220 221 /* 222 * Maximum number of entries that will be allocated in one piece, if 223 * a list larger than this is required then chaining will be utilized. 224 */ 225 #define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist)) 226 227 228 /* 229 * Mapping sg iterator 230 * 231 * Iterates over sg entries mapping page-by-page. On each successful 232 * iteration, @miter->page points to the mapped page and 233 * @miter->length bytes of data can be accessed at @miter->addr. As 234 * long as an interation is enclosed between start and stop, the user 235 * is free to choose control structure and when to stop. 236 * 237 * @miter->consumed is set to @miter->length on each iteration. It 238 * can be adjusted if the user can't consume all the bytes in one go. 239 * Also, a stopped iteration can be resumed by calling next on it. 240 * This is useful when iteration needs to release all resources and 241 * continue later (e.g. at the next interrupt). 242 */ 243 244 #define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */ 245 #define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */ 246 #define SG_MITER_FROM_SG (1 << 2) /* nop */ 247 248 struct sg_mapping_iter { 249 /* the following three fields can be accessed directly */ 250 struct page *page; /* currently mapped page */ 251 void *addr; /* pointer to the mapped area */ 252 size_t length; /* length of the mapped area */ 253 size_t consumed; /* number of consumed bytes */ 254 255 /* these are internal states, keep away */ 256 struct scatterlist *__sg; /* current entry */ 257 unsigned int __nents; /* nr of remaining entries */ 258 unsigned int __offset; /* offset within sg */ 259 unsigned int __flags; 260 }; 261 262 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, 263 unsigned int nents, unsigned int flags); 264 bool sg_miter_next(struct sg_mapping_iter *miter); 265 void sg_miter_stop(struct sg_mapping_iter *miter); 266 267 #endif /* _LINUX_SCATTERLIST_H */ 268