1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _LINUX_SCATTERLIST_H 3 #define _LINUX_SCATTERLIST_H 4 5 #include <linux/string.h> 6 #include <linux/types.h> 7 #include <linux/bug.h> 8 #include <linux/mm.h> 9 #include <asm/io.h> 10 11 struct scatterlist { 12 #ifdef CONFIG_DEBUG_SG 13 unsigned long sg_magic; 14 #endif 15 unsigned long page_link; 16 unsigned int offset; 17 unsigned int length; 18 dma_addr_t dma_address; 19 #ifdef CONFIG_NEED_SG_DMA_LENGTH 20 unsigned int dma_length; 21 #endif 22 }; 23 24 /* 25 * These macros should be used after a dma_map_sg call has been done 26 * to get bus addresses of each of the SG entries and their lengths. 27 * You should only work with the number of sg entries dma_map_sg 28 * returns, or alternatively stop on the first sg_dma_len(sg) which 29 * is 0. 30 */ 31 #define sg_dma_address(sg) ((sg)->dma_address) 32 33 #ifdef CONFIG_NEED_SG_DMA_LENGTH 34 #define sg_dma_len(sg) ((sg)->dma_length) 35 #else 36 #define sg_dma_len(sg) ((sg)->length) 37 #endif 38 39 struct sg_table { 40 struct scatterlist *sgl; /* the list */ 41 unsigned int nents; /* number of mapped entries */ 42 unsigned int orig_nents; /* original size of list */ 43 }; 44 45 /* 46 * Notes on SG table design. 47 * 48 * We use the unsigned long page_link field in the scatterlist struct to place 49 * the page pointer AND encode information about the sg table as well. The two 50 * lower bits are reserved for this information. 51 * 52 * If bit 0 is set, then the page_link contains a pointer to the next sg 53 * table list. Otherwise the next entry is at sg + 1. 54 * 55 * If bit 1 is set, then this sg entry is the last element in a list. 56 * 57 * See sg_next(). 58 * 59 */ 60 61 #define SG_MAGIC 0x87654321 62 63 /* 64 * We overload the LSB of the page pointer to indicate whether it's 65 * a valid sg entry, or whether it points to the start of a new scatterlist. 66 * Those low bits are there for everyone! (thanks mason :-) 67 */ 68 #define sg_is_chain(sg) ((sg)->page_link & 0x01) 69 #define sg_is_last(sg) ((sg)->page_link & 0x02) 70 #define sg_chain_ptr(sg) \ 71 ((struct scatterlist *) ((sg)->page_link & ~0x03)) 72 73 /** 74 * sg_assign_page - Assign a given page to an SG entry 75 * @sg: SG entry 76 * @page: The page 77 * 78 * Description: 79 * Assign page to sg entry. Also see sg_set_page(), the most commonly used 80 * variant. 81 * 82 **/ 83 static inline void sg_assign_page(struct scatterlist *sg, struct page *page) 84 { 85 unsigned long page_link = sg->page_link & 0x3; 86 87 /* 88 * In order for the low bit stealing approach to work, pages 89 * must be aligned at a 32-bit boundary as a minimum. 90 */ 91 BUG_ON((unsigned long) page & 0x03); 92 #ifdef CONFIG_DEBUG_SG 93 BUG_ON(sg->sg_magic != SG_MAGIC); 94 BUG_ON(sg_is_chain(sg)); 95 #endif 96 sg->page_link = page_link | (unsigned long) page; 97 } 98 99 /** 100 * sg_set_page - Set sg entry to point at given page 101 * @sg: SG entry 102 * @page: The page 103 * @len: Length of data 104 * @offset: Offset into page 105 * 106 * Description: 107 * Use this function to set an sg entry pointing at a page, never assign 108 * the page directly. We encode sg table information in the lower bits 109 * of the page pointer. See sg_page() for looking up the page belonging 110 * to an sg entry. 111 * 112 **/ 113 static inline void sg_set_page(struct scatterlist *sg, struct page *page, 114 unsigned int len, unsigned int offset) 115 { 116 sg_assign_page(sg, page); 117 sg->offset = offset; 118 sg->length = len; 119 } 120 121 static inline struct page *sg_page(struct scatterlist *sg) 122 { 123 #ifdef CONFIG_DEBUG_SG 124 BUG_ON(sg->sg_magic != SG_MAGIC); 125 BUG_ON(sg_is_chain(sg)); 126 #endif 127 return (struct page *)((sg)->page_link & ~0x3); 128 } 129 130 /** 131 * sg_set_buf - Set sg entry to point at given data 132 * @sg: SG entry 133 * @buf: Data 134 * @buflen: Data length 135 * 136 **/ 137 static inline void sg_set_buf(struct scatterlist *sg, const void *buf, 138 unsigned int buflen) 139 { 140 #ifdef CONFIG_DEBUG_SG 141 BUG_ON(!virt_addr_valid(buf)); 142 #endif 143 sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf)); 144 } 145 146 /* 147 * Loop over each sg element, following the pointer to a new list if necessary 148 */ 149 #define for_each_sg(sglist, sg, nr, __i) \ 150 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg)) 151 152 /** 153 * sg_chain - Chain two sglists together 154 * @prv: First scatterlist 155 * @prv_nents: Number of entries in prv 156 * @sgl: Second scatterlist 157 * 158 * Description: 159 * Links @prv@ and @sgl@ together, to form a longer scatterlist. 160 * 161 **/ 162 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, 163 struct scatterlist *sgl) 164 { 165 /* 166 * offset and length are unused for chain entry. Clear them. 167 */ 168 prv[prv_nents - 1].offset = 0; 169 prv[prv_nents - 1].length = 0; 170 171 /* 172 * Set lowest bit to indicate a link pointer, and make sure to clear 173 * the termination bit if it happens to be set. 174 */ 175 prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02; 176 } 177 178 /** 179 * sg_mark_end - Mark the end of the scatterlist 180 * @sg: SG entryScatterlist 181 * 182 * Description: 183 * Marks the passed in sg entry as the termination point for the sg 184 * table. A call to sg_next() on this entry will return NULL. 185 * 186 **/ 187 static inline void sg_mark_end(struct scatterlist *sg) 188 { 189 #ifdef CONFIG_DEBUG_SG 190 BUG_ON(sg->sg_magic != SG_MAGIC); 191 #endif 192 /* 193 * Set termination bit, clear potential chain bit 194 */ 195 sg->page_link |= 0x02; 196 sg->page_link &= ~0x01; 197 } 198 199 /** 200 * sg_unmark_end - Undo setting the end of the scatterlist 201 * @sg: SG entryScatterlist 202 * 203 * Description: 204 * Removes the termination marker from the given entry of the scatterlist. 205 * 206 **/ 207 static inline void sg_unmark_end(struct scatterlist *sg) 208 { 209 #ifdef CONFIG_DEBUG_SG 210 BUG_ON(sg->sg_magic != SG_MAGIC); 211 #endif 212 sg->page_link &= ~0x02; 213 } 214 215 /** 216 * sg_phys - Return physical address of an sg entry 217 * @sg: SG entry 218 * 219 * Description: 220 * This calls page_to_phys() on the page in this sg entry, and adds the 221 * sg offset. The caller must know that it is legal to call page_to_phys() 222 * on the sg page. 223 * 224 **/ 225 static inline dma_addr_t sg_phys(struct scatterlist *sg) 226 { 227 return page_to_phys(sg_page(sg)) + sg->offset; 228 } 229 230 /** 231 * sg_virt - Return virtual address of an sg entry 232 * @sg: SG entry 233 * 234 * Description: 235 * This calls page_address() on the page in this sg entry, and adds the 236 * sg offset. The caller must know that the sg page has a valid virtual 237 * mapping. 238 * 239 **/ 240 static inline void *sg_virt(struct scatterlist *sg) 241 { 242 return page_address(sg_page(sg)) + sg->offset; 243 } 244 245 int sg_nents(struct scatterlist *sg); 246 int sg_nents_for_len(struct scatterlist *sg, u64 len); 247 struct scatterlist *sg_next(struct scatterlist *); 248 struct scatterlist *sg_last(struct scatterlist *s, unsigned int); 249 void sg_init_table(struct scatterlist *, unsigned int); 250 void sg_init_one(struct scatterlist *, const void *, unsigned int); 251 int sg_split(struct scatterlist *in, const int in_mapped_nents, 252 const off_t skip, const int nb_splits, 253 const size_t *split_sizes, 254 struct scatterlist **out, int *out_mapped_nents, 255 gfp_t gfp_mask); 256 257 typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t); 258 typedef void (sg_free_fn)(struct scatterlist *, unsigned int); 259 260 void __sg_free_table(struct sg_table *, unsigned int, bool, sg_free_fn *); 261 void sg_free_table(struct sg_table *); 262 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, 263 struct scatterlist *, gfp_t, sg_alloc_fn *); 264 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t); 265 int sg_alloc_table_from_pages(struct sg_table *sgt, 266 struct page **pages, unsigned int n_pages, 267 unsigned long offset, unsigned long size, 268 gfp_t gfp_mask); 269 270 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf, 271 size_t buflen, off_t skip, bool to_buffer); 272 273 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, 274 const void *buf, size_t buflen); 275 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, 276 void *buf, size_t buflen); 277 278 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents, 279 const void *buf, size_t buflen, off_t skip); 280 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents, 281 void *buf, size_t buflen, off_t skip); 282 size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents, 283 size_t buflen, off_t skip); 284 285 /* 286 * Maximum number of entries that will be allocated in one piece, if 287 * a list larger than this is required then chaining will be utilized. 288 */ 289 #define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist)) 290 291 /* 292 * The maximum number of SG segments that we will put inside a 293 * scatterlist (unless chaining is used). Should ideally fit inside a 294 * single page, to avoid a higher order allocation. We could define this 295 * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order. The 296 * minimum value is 32 297 */ 298 #define SG_CHUNK_SIZE 128 299 300 /* 301 * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit 302 * is totally arbitrary, a setting of 2048 will get you at least 8mb ios. 303 */ 304 #ifdef CONFIG_ARCH_HAS_SG_CHAIN 305 #define SG_MAX_SEGMENTS 2048 306 #else 307 #define SG_MAX_SEGMENTS SG_CHUNK_SIZE 308 #endif 309 310 #ifdef CONFIG_SG_POOL 311 void sg_free_table_chained(struct sg_table *table, bool first_chunk); 312 int sg_alloc_table_chained(struct sg_table *table, int nents, 313 struct scatterlist *first_chunk); 314 #endif 315 316 /* 317 * sg page iterator 318 * 319 * Iterates over sg entries page-by-page. On each successful iteration, 320 * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter) 321 * to get the current page and its dma address. @piter->sg will point to the 322 * sg holding this page and @piter->sg_pgoffset to the page's page offset 323 * within the sg. The iteration will stop either when a maximum number of sg 324 * entries was reached or a terminating sg (sg_last(sg) == true) was reached. 325 */ 326 struct sg_page_iter { 327 struct scatterlist *sg; /* sg holding the page */ 328 unsigned int sg_pgoffset; /* page offset within the sg */ 329 330 /* these are internal states, keep away */ 331 unsigned int __nents; /* remaining sg entries */ 332 int __pg_advance; /* nr pages to advance at the 333 * next step */ 334 }; 335 336 bool __sg_page_iter_next(struct sg_page_iter *piter); 337 void __sg_page_iter_start(struct sg_page_iter *piter, 338 struct scatterlist *sglist, unsigned int nents, 339 unsigned long pgoffset); 340 /** 341 * sg_page_iter_page - get the current page held by the page iterator 342 * @piter: page iterator holding the page 343 */ 344 static inline struct page *sg_page_iter_page(struct sg_page_iter *piter) 345 { 346 return nth_page(sg_page(piter->sg), piter->sg_pgoffset); 347 } 348 349 /** 350 * sg_page_iter_dma_address - get the dma address of the current page held by 351 * the page iterator. 352 * @piter: page iterator holding the page 353 */ 354 static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter) 355 { 356 return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT); 357 } 358 359 /** 360 * for_each_sg_page - iterate over the pages of the given sg list 361 * @sglist: sglist to iterate over 362 * @piter: page iterator to hold current page, sg, sg_pgoffset 363 * @nents: maximum number of sg entries to iterate over 364 * @pgoffset: starting page offset 365 */ 366 #define for_each_sg_page(sglist, piter, nents, pgoffset) \ 367 for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \ 368 __sg_page_iter_next(piter);) 369 370 /* 371 * Mapping sg iterator 372 * 373 * Iterates over sg entries mapping page-by-page. On each successful 374 * iteration, @miter->page points to the mapped page and 375 * @miter->length bytes of data can be accessed at @miter->addr. As 376 * long as an interation is enclosed between start and stop, the user 377 * is free to choose control structure and when to stop. 378 * 379 * @miter->consumed is set to @miter->length on each iteration. It 380 * can be adjusted if the user can't consume all the bytes in one go. 381 * Also, a stopped iteration can be resumed by calling next on it. 382 * This is useful when iteration needs to release all resources and 383 * continue later (e.g. at the next interrupt). 384 */ 385 386 #define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */ 387 #define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */ 388 #define SG_MITER_FROM_SG (1 << 2) /* nop */ 389 390 struct sg_mapping_iter { 391 /* the following three fields can be accessed directly */ 392 struct page *page; /* currently mapped page */ 393 void *addr; /* pointer to the mapped area */ 394 size_t length; /* length of the mapped area */ 395 size_t consumed; /* number of consumed bytes */ 396 struct sg_page_iter piter; /* page iterator */ 397 398 /* these are internal states, keep away */ 399 unsigned int __offset; /* offset within page */ 400 unsigned int __remaining; /* remaining bytes on page */ 401 unsigned int __flags; 402 }; 403 404 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, 405 unsigned int nents, unsigned int flags); 406 bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset); 407 bool sg_miter_next(struct sg_mapping_iter *miter); 408 void sg_miter_stop(struct sg_mapping_iter *miter); 409 410 #endif /* _LINUX_SCATTERLIST_H */ 411