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 /* 11 * Notes on SG table design. 12 * 13 * Architectures must provide an unsigned long page_link field in the 14 * scatterlist struct. We use that to place the page pointer AND encode 15 * information about the sg table as well. The two lower bits are reserved 16 * for this information. 17 * 18 * If bit 0 is set, then the page_link contains a pointer to the next sg 19 * table list. Otherwise the next entry is at sg + 1. 20 * 21 * If bit 1 is set, then this sg entry is the last element in a list. 22 * 23 * See sg_next(). 24 * 25 */ 26 27 #define SG_MAGIC 0x87654321 28 29 /* 30 * We overload the LSB of the page pointer to indicate whether it's 31 * a valid sg entry, or whether it points to the start of a new scatterlist. 32 * Those low bits are there for everyone! (thanks mason :-) 33 */ 34 #define sg_is_chain(sg) ((sg)->page_link & 0x01) 35 #define sg_is_last(sg) ((sg)->page_link & 0x02) 36 #define sg_chain_ptr(sg) \ 37 ((struct scatterlist *) ((sg)->page_link & ~0x03)) 38 39 /** 40 * sg_assign_page - Assign a given page to an SG entry 41 * @sg: SG entry 42 * @page: The page 43 * 44 * Description: 45 * Assign page to sg entry. Also see sg_set_page(), the most commonly used 46 * variant. 47 * 48 **/ 49 static inline void sg_assign_page(struct scatterlist *sg, struct page *page) 50 { 51 unsigned long page_link = sg->page_link & 0x3; 52 53 /* 54 * In order for the low bit stealing approach to work, pages 55 * must be aligned at a 32-bit boundary as a minimum. 56 */ 57 BUG_ON((unsigned long) page & 0x03); 58 #ifdef CONFIG_DEBUG_SG 59 BUG_ON(sg->sg_magic != SG_MAGIC); 60 BUG_ON(sg_is_chain(sg)); 61 #endif 62 sg->page_link = page_link | (unsigned long) page; 63 } 64 65 /** 66 * sg_set_page - Set sg entry to point at given page 67 * @sg: SG entry 68 * @page: The page 69 * @len: Length of data 70 * @offset: Offset into page 71 * 72 * Description: 73 * Use this function to set an sg entry pointing at a page, never assign 74 * the page directly. We encode sg table information in the lower bits 75 * of the page pointer. See sg_page() for looking up the page belonging 76 * to an sg entry. 77 * 78 **/ 79 static inline void sg_set_page(struct scatterlist *sg, struct page *page, 80 unsigned int len, unsigned int offset) 81 { 82 sg_assign_page(sg, page); 83 sg->offset = offset; 84 sg->length = len; 85 } 86 87 static inline struct page *sg_page(struct scatterlist *sg) 88 { 89 #ifdef CONFIG_DEBUG_SG 90 BUG_ON(sg->sg_magic != SG_MAGIC); 91 BUG_ON(sg_is_chain(sg)); 92 #endif 93 return (struct page *)((sg)->page_link & ~0x3); 94 } 95 96 /** 97 * sg_set_buf - Set sg entry to point at given data 98 * @sg: SG entry 99 * @buf: Data 100 * @buflen: Data length 101 * 102 **/ 103 static inline void sg_set_buf(struct scatterlist *sg, const void *buf, 104 unsigned int buflen) 105 { 106 sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf)); 107 } 108 109 /** 110 * sg_next - return the next scatterlist entry in a list 111 * @sg: The current sg entry 112 * 113 * Description: 114 * Usually the next entry will be @sg@ + 1, but if this sg element is part 115 * of a chained scatterlist, it could jump to the start of a new 116 * scatterlist array. 117 * 118 **/ 119 static inline struct scatterlist *sg_next(struct scatterlist *sg) 120 { 121 #ifdef CONFIG_DEBUG_SG 122 BUG_ON(sg->sg_magic != SG_MAGIC); 123 #endif 124 if (sg_is_last(sg)) 125 return NULL; 126 127 sg++; 128 if (unlikely(sg_is_chain(sg))) 129 sg = sg_chain_ptr(sg); 130 131 return sg; 132 } 133 134 /* 135 * Loop over each sg element, following the pointer to a new list if necessary 136 */ 137 #define for_each_sg(sglist, sg, nr, __i) \ 138 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg)) 139 140 /** 141 * sg_last - return the last scatterlist entry in a list 142 * @sgl: First entry in the scatterlist 143 * @nents: Number of entries in the scatterlist 144 * 145 * Description: 146 * Should only be used casually, it (currently) scan the entire list 147 * to get the last entry. 148 * 149 * Note that the @sgl@ pointer passed in need not be the first one, 150 * the important bit is that @nents@ denotes the number of entries that 151 * exist from @sgl@. 152 * 153 **/ 154 static inline struct scatterlist *sg_last(struct scatterlist *sgl, 155 unsigned int nents) 156 { 157 #ifndef ARCH_HAS_SG_CHAIN 158 struct scatterlist *ret = &sgl[nents - 1]; 159 #else 160 struct scatterlist *sg, *ret = NULL; 161 unsigned int i; 162 163 for_each_sg(sgl, sg, nents, i) 164 ret = sg; 165 166 #endif 167 #ifdef CONFIG_DEBUG_SG 168 BUG_ON(sgl[0].sg_magic != SG_MAGIC); 169 BUG_ON(!sg_is_last(ret)); 170 #endif 171 return ret; 172 } 173 174 /** 175 * sg_chain - Chain two sglists together 176 * @prv: First scatterlist 177 * @prv_nents: Number of entries in prv 178 * @sgl: Second scatterlist 179 * 180 * Description: 181 * Links @prv@ and @sgl@ together, to form a longer scatterlist. 182 * 183 **/ 184 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, 185 struct scatterlist *sgl) 186 { 187 #ifndef ARCH_HAS_SG_CHAIN 188 BUG(); 189 #endif 190 191 /* 192 * offset and length are unused for chain entry. Clear them. 193 */ 194 prv->offset = 0; 195 prv->length = 0; 196 197 /* 198 * Set lowest bit to indicate a link pointer, and make sure to clear 199 * the termination bit if it happens to be set. 200 */ 201 prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02; 202 } 203 204 /** 205 * sg_mark_end - Mark the end of the scatterlist 206 * @sg: SG entryScatterlist 207 * 208 * Description: 209 * Marks the passed in sg entry as the termination point for the sg 210 * table. A call to sg_next() on this entry will return NULL. 211 * 212 **/ 213 static inline void sg_mark_end(struct scatterlist *sg) 214 { 215 #ifdef CONFIG_DEBUG_SG 216 BUG_ON(sg->sg_magic != SG_MAGIC); 217 #endif 218 /* 219 * Set termination bit, clear potential chain bit 220 */ 221 sg->page_link |= 0x02; 222 sg->page_link &= ~0x01; 223 } 224 225 /** 226 * sg_init_table - Initialize SG table 227 * @sgl: The SG table 228 * @nents: Number of entries in table 229 * 230 * Notes: 231 * If this is part of a chained sg table, sg_mark_end() should be 232 * used only on the last table part. 233 * 234 **/ 235 static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents) 236 { 237 memset(sgl, 0, sizeof(*sgl) * nents); 238 #ifdef CONFIG_DEBUG_SG 239 { 240 unsigned int i; 241 for (i = 0; i < nents; i++) 242 sgl[i].sg_magic = SG_MAGIC; 243 } 244 #endif 245 sg_mark_end(&sgl[nents - 1]); 246 } 247 248 /** 249 * sg_init_one - Initialize a single entry sg list 250 * @sg: SG entry 251 * @buf: Virtual address for IO 252 * @buflen: IO length 253 * 254 * Notes: 255 * This should not be used on a single entry that is part of a larger 256 * table. Use sg_init_table() for that. 257 * 258 **/ 259 static inline void sg_init_one(struct scatterlist *sg, const void *buf, 260 unsigned int buflen) 261 { 262 sg_init_table(sg, 1); 263 sg_set_buf(sg, buf, buflen); 264 } 265 266 /** 267 * sg_phys - Return physical address of an sg entry 268 * @sg: SG entry 269 * 270 * Description: 271 * This calls page_to_phys() on the page in this sg entry, and adds the 272 * sg offset. The caller must know that it is legal to call page_to_phys() 273 * on the sg page. 274 * 275 **/ 276 static inline dma_addr_t sg_phys(struct scatterlist *sg) 277 { 278 return page_to_phys(sg_page(sg)) + sg->offset; 279 } 280 281 /** 282 * sg_virt - Return virtual address of an sg entry 283 * @sg: SG entry 284 * 285 * Description: 286 * This calls page_address() on the page in this sg entry, and adds the 287 * sg offset. The caller must know that the sg page has a valid virtual 288 * mapping. 289 * 290 **/ 291 static inline void *sg_virt(struct scatterlist *sg) 292 { 293 return page_address(sg_page(sg)) + sg->offset; 294 } 295 296 #endif /* _LINUX_SCATTERLIST_H */ 297