include/linux/scatterlist.h

   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         unsigned long   page_link;
  13         unsigned int    offset;
  14         unsigned int    length;
  15         dma_addr_t      dma_address;
  16 #ifdef CONFIG_NEED_SG_DMA_LENGTH
  17         unsigned int    dma_length;
  18 #endif
  19 };
  20
  21 /*
  22  * These macros should be used after a dma_map_sg call has been done
  23  * to get bus addresses of each of the SG entries and their lengths.
  24  * You should only work with the number of sg entries dma_map_sg
  25  * returns, or alternatively stop on the first sg_dma_len(sg) which
  26  * is 0.
  27  */
  28 #define sg_dma_address(sg)      ((sg)->dma_address)
  29
  30 #ifdef CONFIG_NEED_SG_DMA_LENGTH
  31 #define sg_dma_len(sg)          ((sg)->dma_length)
  32 #else
  33 #define sg_dma_len(sg)          ((sg)->length)
  34 #endif
  35
  36 struct sg_table {
  37         struct scatterlist *sgl;        /* the list */
  38         unsigned int nents;             /* number of mapped entries */
  39         unsigned int orig_nents;        /* original size of list */
  40 };
  41
  42 struct sg_append_table {
  43         struct sg_table sgt;            /* The scatter list table */
  44         struct scatterlist *prv;        /* last populated sge in the table */
  45         unsigned int total_nents;       /* Total entries in the table */
  46 };
  47
  48 /*
  49  * Notes on SG table design.
  50  *
  51  * We use the unsigned long page_link field in the scatterlist struct to place
  52  * the page pointer AND encode information about the sg table as well. The two
  53  * lower bits are reserved for this information.
  54  *
  55  * If bit 0 is set, then the page_link contains a pointer to the next sg
  56  * table list. Otherwise the next entry is at sg + 1.
  57  *
  58  * If bit 1 is set, then this sg entry is the last element in a list.
  59  *
  60  * See sg_next().
  61  *
  62  */
  63
  64 #define SG_CHAIN        0x01UL
  65 #define SG_END          0x02UL
  66
  67 /*
  68  * We overload the LSB of the page pointer to indicate whether it's
  69  * a valid sg entry, or whether it points to the start of a new scatterlist.
  70  * Those low bits are there for everyone! (thanks mason :-)
  71  */
  72 #define sg_is_chain(sg)         ((sg)->page_link & SG_CHAIN)
  73 #define sg_is_last(sg)          ((sg)->page_link & SG_END)
  74 #define sg_chain_ptr(sg)        \
  75         ((struct scatterlist *) ((sg)->page_link & ~(SG_CHAIN | SG_END)))
  76
  77 /**
  78  * sg_assign_page - Assign a given page to an SG entry
  79  * @sg:             SG entry
  80  * @page:           The page
  81  *
  82  * Description:
  83  *   Assign page to sg entry. Also see sg_set_page(), the most commonly used
  84  *   variant.
  85  *
  86  **/
  87 static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
  88 {
  89         unsigned long page_link = sg->page_link & (SG_CHAIN | SG_END);
  90
  91         /*
  92          * In order for the low bit stealing approach to work, pages
  93          * must be aligned at a 32-bit boundary as a minimum.
  94          */
  95         BUG_ON((unsigned long) page & (SG_CHAIN | SG_END));
  96 #ifdef CONFIG_DEBUG_SG
  97         BUG_ON(sg_is_chain(sg));
  98 #endif
  99         sg->page_link = page_link | (unsigned long) page;
 100 }
 101
 102 /**
 103  * sg_set_page - Set sg entry to point at given page
 104  * @sg:          SG entry
 105  * @page:        The page
 106  * @len:         Length of data
 107  * @offset:      Offset into page
 108  *
 109  * Description:
 110  *   Use this function to set an sg entry pointing at a page, never assign
 111  *   the page directly. We encode sg table information in the lower bits
 112  *   of the page pointer. See sg_page() for looking up the page belonging
 113  *   to an sg entry.
 114  *
 115  **/
 116 static inline void sg_set_page(struct scatterlist *sg, struct page *page,
 117                                unsigned int len, unsigned int offset)
 118 {
 119         sg_assign_page(sg, page);
 120         sg->offset = offset;
 121         sg->length = len;
 122 }
 123
 124 static inline struct page *sg_page(struct scatterlist *sg)
 125 {
 126 #ifdef CONFIG_DEBUG_SG
 127         BUG_ON(sg_is_chain(sg));
 128 #endif
 129         return (struct page *)((sg)->page_link & ~(SG_CHAIN | SG_END));
 130 }
 131
 132 /**
 133  * sg_set_buf - Set sg entry to point at given data
 134  * @sg:          SG entry
 135  * @buf:         Data
 136  * @buflen:      Data length
 137  *
 138  **/
 139 static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
 140                               unsigned int buflen)
 141 {
 142 #ifdef CONFIG_DEBUG_SG
 143         BUG_ON(!virt_addr_valid(buf));
 144 #endif
 145         sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
 146 }
 147
 148 /*
 149  * Loop over each sg element, following the pointer to a new list if necessary
 150  */
 151 #define for_each_sg(sglist, sg, nr, __i)        \
 152         for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
 153
 154 /*
 155  * Loop over each sg element in the given sg_table object.
 156  */
 157 #define for_each_sgtable_sg(sgt, sg, i)         \
 158         for_each_sg((sgt)->sgl, sg, (sgt)->orig_nents, i)
 159
 160 /*
 161  * Loop over each sg element in the given *DMA mapped* sg_table object.
 162  * Please use sg_dma_address(sg) and sg_dma_len(sg) to extract DMA addresses
 163  * of the each element.
 164  */
 165 #define for_each_sgtable_dma_sg(sgt, sg, i)     \
 166         for_each_sg((sgt)->sgl, sg, (sgt)->nents, i)
 167
 168 static inline void __sg_chain(struct scatterlist *chain_sg,
 169                               struct scatterlist *sgl)
 170 {
 171         /*
 172          * offset and length are unused for chain entry. Clear them.
 173          */
 174         chain_sg->offset = 0;
 175         chain_sg->length = 0;
 176
 177         /*
 178          * Set lowest bit to indicate a link pointer, and make sure to clear
 179          * the termination bit if it happens to be set.
 180          */
 181         chain_sg->page_link = ((unsigned long) sgl | SG_CHAIN) & ~SG_END;
 182 }
 183
 184 /**
 185  * sg_chain - Chain two sglists together
 186  * @prv:        First scatterlist
 187  * @prv_nents:  Number of entries in prv
 188  * @sgl:        Second scatterlist
 189  *
 190  * Description:
 191  *   Links @prv@ and @sgl@ together, to form a longer scatterlist.
 192  *
 193  **/
 194 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
 195                             struct scatterlist *sgl)
 196 {
 197         __sg_chain(&prv[prv_nents - 1], sgl);
 198 }
 199
 200 /**
 201  * sg_mark_end - Mark the end of the scatterlist
 202  * @sg:          SG entryScatterlist
 203  *
 204  * Description:
 205  *   Marks the passed in sg entry as the termination point for the sg
 206  *   table. A call to sg_next() on this entry will return NULL.
 207  *
 208  **/
 209 static inline void sg_mark_end(struct scatterlist *sg)
 210 {
 211         /*
 212          * Set termination bit, clear potential chain bit
 213          */
 214         sg->page_link |= SG_END;
 215         sg->page_link &= ~SG_CHAIN;
 216 }
 217
 218 /**
 219  * sg_unmark_end - Undo setting the end of the scatterlist
 220  * @sg:          SG entryScatterlist
 221  *
 222  * Description:
 223  *   Removes the termination marker from the given entry of the scatterlist.
 224  *
 225  **/
 226 static inline void sg_unmark_end(struct scatterlist *sg)
 227 {
 228         sg->page_link &= ~SG_END;
 229 }
 230
 231 /**
 232  * sg_phys - Return physical address of an sg entry
 233  * @sg:      SG entry
 234  *
 235  * Description:
 236  *   This calls page_to_phys() on the page in this sg entry, and adds the
 237  *   sg offset. The caller must know that it is legal to call page_to_phys()
 238  *   on the sg page.
 239  *
 240  **/
 241 static inline dma_addr_t sg_phys(struct scatterlist *sg)
 242 {
 243         return page_to_phys(sg_page(sg)) + sg->offset;
 244 }
 245
 246 /**
 247  * sg_virt - Return virtual address of an sg entry
 248  * @sg:      SG entry
 249  *
 250  * Description:
 251  *   This calls page_address() on the page in this sg entry, and adds the
 252  *   sg offset. The caller must know that the sg page has a valid virtual
 253  *   mapping.
 254  *
 255  **/
 256 static inline void *sg_virt(struct scatterlist *sg)
 257 {
 258         return page_address(sg_page(sg)) + sg->offset;
 259 }
 260
 261 /**
 262  * sg_init_marker - Initialize markers in sg table
 263  * @sgl:           The SG table
 264  * @nents:         Number of entries in table
 265  *
 266  **/
 267 static inline void sg_init_marker(struct scatterlist *sgl,
 268                                   unsigned int nents)
 269 {
 270         sg_mark_end(&sgl[nents - 1]);
 271 }
 272
 273 int sg_nents(struct scatterlist *sg);
 274 int sg_nents_for_len(struct scatterlist *sg, u64 len);
 275 struct scatterlist *sg_next(struct scatterlist *);
 276 struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
 277 void sg_init_table(struct scatterlist *, unsigned int);
 278 void sg_init_one(struct scatterlist *, const void *, unsigned int);
 279 int sg_split(struct scatterlist *in, const int in_mapped_nents,
 280              const off_t skip, const int nb_splits,
 281              const size_t *split_sizes,
 282              struct scatterlist **out, int *out_mapped_nents,
 283              gfp_t gfp_mask);
 284
 285 typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
 286 typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
 287
 288 void __sg_free_table(struct sg_table *, unsigned int, unsigned int,
 289                      sg_free_fn *, unsigned int);
 290 void sg_free_table(struct sg_table *);
 291 void sg_free_append_table(struct sg_append_table *sgt);
 292 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
 293                      struct scatterlist *, unsigned int, gfp_t, sg_alloc_fn *);
 294 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
 295 int sg_alloc_append_table_from_pages(struct sg_append_table *sgt,
 296                                      struct page **pages, unsigned int n_pages,
 297                                      unsigned int offset, unsigned long size,
 298                                      unsigned int max_segment,
 299                                      unsigned int left_pages, gfp_t gfp_mask);
 300 int sg_alloc_table_from_pages_segment(struct sg_table *sgt, struct page **pages,
 301                                       unsigned int n_pages, unsigned int offset,
 302                                       unsigned long size,
 303                                       unsigned int max_segment, gfp_t gfp_mask);
 304
 305 /**
 306  * sg_alloc_table_from_pages - Allocate and initialize an sg table from
 307  *                             an array of pages
 308  * @sgt:         The sg table header to use
 309  * @pages:       Pointer to an array of page pointers
 310  * @n_pages:     Number of pages in the pages array
 311  * @offset:      Offset from start of the first page to the start of a buffer
 312  * @size:        Number of valid bytes in the buffer (after offset)
 313  * @gfp_mask:    GFP allocation mask
 314  *
 315  *  Description:
 316  *    Allocate and initialize an sg table from a list of pages. Contiguous
 317  *    ranges of the pages are squashed into a single scatterlist node. A user
 318  *    may provide an offset at a start and a size of valid data in a buffer
 319  *    specified by the page array. The returned sg table is released by
 320  *    sg_free_table.
 321  *
 322  * Returns:
 323  *   0 on success, negative error on failure
 324  */
 325 static inline int sg_alloc_table_from_pages(struct sg_table *sgt,
 326                                             struct page **pages,
 327                                             unsigned int n_pages,
 328                                             unsigned int offset,
 329                                             unsigned long size, gfp_t gfp_mask)
 330 {
 331         return sg_alloc_table_from_pages_segment(sgt, pages, n_pages, offset,
 332                                                  size, UINT_MAX, gfp_mask);
 333 }
 334
 335 #ifdef CONFIG_SGL_ALLOC
 336 struct scatterlist *sgl_alloc_order(unsigned long long length,
 337                                     unsigned int order, bool chainable,
 338                                     gfp_t gfp, unsigned int *nent_p);
 339 struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
 340                               unsigned int *nent_p);
 341 void sgl_free_n_order(struct scatterlist *sgl, int nents, int order);
 342 void sgl_free_order(struct scatterlist *sgl, int order);
 343 void sgl_free(struct scatterlist *sgl);
 344 #endif /* CONFIG_SGL_ALLOC */
 345
 346 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
 347                       size_t buflen, off_t skip, bool to_buffer);
 348
 349 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 350                            const void *buf, size_t buflen);
 351 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 352                          void *buf, size_t buflen);
 353
 354 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 355                             const void *buf, size_t buflen, off_t skip);
 356 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 357                           void *buf, size_t buflen, off_t skip);
 358 size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
 359                        size_t buflen, off_t skip);
 360
 361 /*
 362  * Maximum number of entries that will be allocated in one piece, if
 363  * a list larger than this is required then chaining will be utilized.
 364  */
 365 #define SG_MAX_SINGLE_ALLOC             (PAGE_SIZE / sizeof(struct scatterlist))
 366
 367 /*
 368  * The maximum number of SG segments that we will put inside a
 369  * scatterlist (unless chaining is used). Should ideally fit inside a
 370  * single page, to avoid a higher order allocation.  We could define this
 371  * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order.  The
 372  * minimum value is 32
 373  */
 374 #define SG_CHUNK_SIZE   128
 375
 376 /*
 377  * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
 378  * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
 379  */
 380 #ifdef CONFIG_ARCH_NO_SG_CHAIN
 381 #define SG_MAX_SEGMENTS SG_CHUNK_SIZE
 382 #else
 383 #define SG_MAX_SEGMENTS 2048
 384 #endif
 385
 386 #ifdef CONFIG_SG_POOL
 387 void sg_free_table_chained(struct sg_table *table,
 388                            unsigned nents_first_chunk);
 389 int sg_alloc_table_chained(struct sg_table *table, int nents,
 390                            struct scatterlist *first_chunk,
 391                            unsigned nents_first_chunk);
 392 #endif
 393
 394 /*
 395  * sg page iterator
 396  *
 397  * Iterates over sg entries page-by-page.  On each successful iteration, you
 398  * can call sg_page_iter_page(@piter) to get the current page.
 399  * @piter->sg will point to the sg holding this page and @piter->sg_pgoffset to
 400  * the page's page offset within the sg. The iteration will stop either when a
 401  * maximum number of sg entries was reached or a terminating sg
 402  * (sg_last(sg) == true) was reached.
 403  */
 404 struct sg_page_iter {
 405         struct scatterlist      *sg;            /* sg holding the page */
 406         unsigned int            sg_pgoffset;    /* page offset within the sg */
 407
 408         /* these are internal states, keep away */
 409         unsigned int            __nents;        /* remaining sg entries */
 410         int                     __pg_advance;   /* nr pages to advance at the
 411                                                  * next step */
 412 };
 413
 414 /*
 415  * sg page iterator for DMA addresses
 416  *
 417  * This is the same as sg_page_iter however you can call
 418  * sg_page_iter_dma_address(@dma_iter) to get the page's DMA
 419  * address. sg_page_iter_page() cannot be called on this iterator.
 420  */
 421 struct sg_dma_page_iter {
 422         struct sg_page_iter base;
 423 };
 424
 425 bool __sg_page_iter_next(struct sg_page_iter *piter);
 426 bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter);
 427 void __sg_page_iter_start(struct sg_page_iter *piter,
 428                           struct scatterlist *sglist, unsigned int nents,
 429                           unsigned long pgoffset);
 430 /**
 431  * sg_page_iter_page - get the current page held by the page iterator
 432  * @piter:      page iterator holding the page
 433  */
 434 static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
 435 {
 436         return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
 437 }
 438
 439 /**
 440  * sg_page_iter_dma_address - get the dma address of the current page held by
 441  * the page iterator.
 442  * @dma_iter:   page iterator holding the page
 443  */
 444 static inline dma_addr_t
 445 sg_page_iter_dma_address(struct sg_dma_page_iter *dma_iter)
 446 {
 447         return sg_dma_address(dma_iter->base.sg) +
 448                (dma_iter->base.sg_pgoffset << PAGE_SHIFT);
 449 }
 450
 451 /**
 452  * for_each_sg_page - iterate over the pages of the given sg list
 453  * @sglist:     sglist to iterate over
 454  * @piter:      page iterator to hold current page, sg, sg_pgoffset
 455  * @nents:      maximum number of sg entries to iterate over
 456  * @pgoffset:   starting page offset (in pages)
 457  *
 458  * Callers may use sg_page_iter_page() to get each page pointer.
 459  * In each loop it operates on PAGE_SIZE unit.
 460  */
 461 #define for_each_sg_page(sglist, piter, nents, pgoffset)                   \
 462         for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
 463              __sg_page_iter_next(piter);)
 464
 465 /**
 466  * for_each_sg_dma_page - iterate over the pages of the given sg list
 467  * @sglist:     sglist to iterate over
 468  * @dma_iter:   DMA page iterator to hold current page
 469  * @dma_nents:  maximum number of sg entries to iterate over, this is the value
 470  *              returned from dma_map_sg
 471  * @pgoffset:   starting page offset (in pages)
 472  *
 473  * Callers may use sg_page_iter_dma_address() to get each page's DMA address.
 474  * In each loop it operates on PAGE_SIZE unit.
 475  */
 476 #define for_each_sg_dma_page(sglist, dma_iter, dma_nents, pgoffset)            \
 477         for (__sg_page_iter_start(&(dma_iter)->base, sglist, dma_nents,        \
 478                                   pgoffset);                                   \
 479              __sg_page_iter_dma_next(dma_iter);)
 480
 481 /**
 482  * for_each_sgtable_page - iterate over all pages in the sg_table object
 483  * @sgt:        sg_table object to iterate over
 484  * @piter:      page iterator to hold current page
 485  * @pgoffset:   starting page offset (in pages)
 486  *
 487  * Iterates over the all memory pages in the buffer described by
 488  * a scatterlist stored in the given sg_table object.
 489  * See also for_each_sg_page(). In each loop it operates on PAGE_SIZE unit.
 490  */
 491 #define for_each_sgtable_page(sgt, piter, pgoffset)     \
 492         for_each_sg_page((sgt)->sgl, piter, (sgt)->orig_nents, pgoffset)
 493
 494 /**
 495  * for_each_sgtable_dma_page - iterate over the DMA mapped sg_table object
 496  * @sgt:        sg_table object to iterate over
 497  * @dma_iter:   DMA page iterator to hold current page
 498  * @pgoffset:   starting page offset (in pages)
 499  *
 500  * Iterates over the all DMA mapped pages in the buffer described by
 501  * a scatterlist stored in the given sg_table object.
 502  * See also for_each_sg_dma_page(). In each loop it operates on PAGE_SIZE
 503  * unit.
 504  */
 505 #define for_each_sgtable_dma_page(sgt, dma_iter, pgoffset)      \
 506         for_each_sg_dma_page((sgt)->sgl, dma_iter, (sgt)->nents, pgoffset)
 507
 508
 509 /*
 510  * Mapping sg iterator
 511  *
 512  * Iterates over sg entries mapping page-by-page.  On each successful
 513  * iteration, @miter->page points to the mapped page and
 514  * @miter->length bytes of data can be accessed at @miter->addr.  As
 515  * long as an iteration is enclosed between start and stop, the user
 516  * is free to choose control structure and when to stop.
 517  *
 518  * @miter->consumed is set to @miter->length on each iteration.  It
 519  * can be adjusted if the user can't consume all the bytes in one go.
 520  * Also, a stopped iteration can be resumed by calling next on it.
 521  * This is useful when iteration needs to release all resources and
 522  * continue later (e.g. at the next interrupt).
 523  */
 524
 525 #define SG_MITER_ATOMIC         (1 << 0)         /* use kmap_atomic */
 526 #define SG_MITER_TO_SG          (1 << 1)        /* flush back to phys on unmap */
 527 #define SG_MITER_FROM_SG        (1 << 2)        /* nop */
 528
 529 struct sg_mapping_iter {
 530         /* the following three fields can be accessed directly */
 531         struct page             *page;          /* currently mapped page */
 532         void                    *addr;          /* pointer to the mapped area */
 533         size_t                  length;         /* length of the mapped area */
 534         size_t                  consumed;       /* number of consumed bytes */
 535         struct sg_page_iter     piter;          /* page iterator */
 536
 537         /* these are internal states, keep away */
 538         unsigned int            __offset;       /* offset within page */
 539         unsigned int            __remaining;    /* remaining bytes on page */
 540         unsigned int            __flags;
 541 };
 542
 543 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
 544                     unsigned int nents, unsigned int flags);
 545 bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
 546 bool sg_miter_next(struct sg_mapping_iter *miter);
 547 void sg_miter_stop(struct sg_mapping_iter *miter);
 548
 549 #endif /* _LINUX_SCATTERLIST_H */