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  * Since the above length field is an unsigned int, below we define the maximum
  23  * length in bytes that can be stored in one scatterlist entry.
  24  */
  25 #define SCATTERLIST_MAX_SEGMENT (UINT_MAX & PAGE_MASK)
  26
  27 /*
  28  * These macros should be used after a dma_map_sg call has been done
  29  * to get bus addresses of each of the SG entries and their lengths.
  30  * You should only work with the number of sg entries dma_map_sg
  31  * returns, or alternatively stop on the first sg_dma_len(sg) which
  32  * is 0.
  33  */
  34 #define sg_dma_address(sg)      ((sg)->dma_address)
  35
  36 #ifdef CONFIG_NEED_SG_DMA_LENGTH
  37 #define sg_dma_len(sg)          ((sg)->dma_length)
  38 #else
  39 #define sg_dma_len(sg)          ((sg)->length)
  40 #endif
  41
  42 struct sg_table {
  43         struct scatterlist *sgl;        /* the list */
  44         unsigned int nents;             /* number of mapped entries */
  45         unsigned int orig_nents;        /* original size of list */
  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  * sg_chain - Chain two sglists together
 156  * @prv:        First scatterlist
 157  * @prv_nents:  Number of entries in prv
 158  * @sgl:        Second scatterlist
 159  *
 160  * Description:
 161  *   Links @prv@ and @sgl@ together, to form a longer scatterlist.
 162  *
 163  **/
 164 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
 165                             struct scatterlist *sgl)
 166 {
 167         /*
 168          * offset and length are unused for chain entry.  Clear them.
 169          */
 170         prv[prv_nents - 1].offset = 0;
 171         prv[prv_nents - 1].length = 0;
 172
 173         /*
 174          * Set lowest bit to indicate a link pointer, and make sure to clear
 175          * the termination bit if it happens to be set.
 176          */
 177         prv[prv_nents - 1].page_link = ((unsigned long) sgl | SG_CHAIN)
 178                                         & ~SG_END;
 179 }
 180
 181 /**
 182  * sg_mark_end - Mark the end of the scatterlist
 183  * @sg:          SG entryScatterlist
 184  *
 185  * Description:
 186  *   Marks the passed in sg entry as the termination point for the sg
 187  *   table. A call to sg_next() on this entry will return NULL.
 188  *
 189  **/
 190 static inline void sg_mark_end(struct scatterlist *sg)
 191 {
 192         /*
 193          * Set termination bit, clear potential chain bit
 194          */
 195         sg->page_link |= SG_END;
 196         sg->page_link &= ~SG_CHAIN;
 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         sg->page_link &= ~SG_END;
 210 }
 211
 212 /**
 213  * sg_phys - Return physical address of an sg entry
 214  * @sg:      SG entry
 215  *
 216  * Description:
 217  *   This calls page_to_phys() on the page in this sg entry, and adds the
 218  *   sg offset. The caller must know that it is legal to call page_to_phys()
 219  *   on the sg page.
 220  *
 221  **/
 222 static inline dma_addr_t sg_phys(struct scatterlist *sg)
 223 {
 224         return page_to_phys(sg_page(sg)) + sg->offset;
 225 }
 226
 227 /**
 228  * sg_virt - Return virtual address of an sg entry
 229  * @sg:      SG entry
 230  *
 231  * Description:
 232  *   This calls page_address() on the page in this sg entry, and adds the
 233  *   sg offset. The caller must know that the sg page has a valid virtual
 234  *   mapping.
 235  *
 236  **/
 237 static inline void *sg_virt(struct scatterlist *sg)
 238 {
 239         return page_address(sg_page(sg)) + sg->offset;
 240 }
 241
 242 /**
 243  * sg_init_marker - Initialize markers in sg table
 244  * @sgl:           The SG table
 245  * @nents:         Number of entries in table
 246  *
 247  **/
 248 static inline void sg_init_marker(struct scatterlist *sgl,
 249                                   unsigned int nents)
 250 {
 251         sg_mark_end(&sgl[nents - 1]);
 252 }
 253
 254 int sg_nents(struct scatterlist *sg);
 255 int sg_nents_for_len(struct scatterlist *sg, u64 len);
 256 struct scatterlist *sg_next(struct scatterlist *);
 257 struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
 258 void sg_init_table(struct scatterlist *, unsigned int);
 259 void sg_init_one(struct scatterlist *, const void *, unsigned int);
 260 int sg_split(struct scatterlist *in, const int in_mapped_nents,
 261              const off_t skip, const int nb_splits,
 262              const size_t *split_sizes,
 263              struct scatterlist **out, int *out_mapped_nents,
 264              gfp_t gfp_mask);
 265
 266 typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
 267 typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
 268
 269 void __sg_free_table(struct sg_table *, unsigned int, unsigned int,
 270                      sg_free_fn *);
 271 void sg_free_table(struct sg_table *);
 272 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
 273                      struct scatterlist *, unsigned int, gfp_t, sg_alloc_fn *);
 274 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
 275 int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
 276                                 unsigned int n_pages, unsigned int offset,
 277                                 unsigned long size, unsigned int max_segment,
 278                                 gfp_t gfp_mask);
 279 int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
 280                               unsigned int n_pages, unsigned int offset,
 281                               unsigned long size, gfp_t gfp_mask);
 282
 283 #ifdef CONFIG_SGL_ALLOC
 284 struct scatterlist *sgl_alloc_order(unsigned long long length,
 285                                     unsigned int order, bool chainable,
 286                                     gfp_t gfp, unsigned int *nent_p);
 287 struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
 288                               unsigned int *nent_p);
 289 void sgl_free_n_order(struct scatterlist *sgl, int nents, int order);
 290 void sgl_free_order(struct scatterlist *sgl, int order);
 291 void sgl_free(struct scatterlist *sgl);
 292 #endif /* CONFIG_SGL_ALLOC */
 293
 294 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
 295                       size_t buflen, off_t skip, bool to_buffer);
 296
 297 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 298                            const void *buf, size_t buflen);
 299 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 300                          void *buf, size_t buflen);
 301
 302 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 303                             const void *buf, size_t buflen, off_t skip);
 304 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 305                           void *buf, size_t buflen, off_t skip);
 306 size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
 307                        size_t buflen, off_t skip);
 308
 309 /*
 310  * Maximum number of entries that will be allocated in one piece, if
 311  * a list larger than this is required then chaining will be utilized.
 312  */
 313 #define SG_MAX_SINGLE_ALLOC             (PAGE_SIZE / sizeof(struct scatterlist))
 314
 315 /*
 316  * The maximum number of SG segments that we will put inside a
 317  * scatterlist (unless chaining is used). Should ideally fit inside a
 318  * single page, to avoid a higher order allocation.  We could define this
 319  * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order.  The
 320  * minimum value is 32
 321  */
 322 #define SG_CHUNK_SIZE   128
 323
 324 /*
 325  * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
 326  * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
 327  */
 328 #ifdef CONFIG_ARCH_NO_SG_CHAIN
 329 #define SG_MAX_SEGMENTS SG_CHUNK_SIZE
 330 #else
 331 #define SG_MAX_SEGMENTS 2048
 332 #endif
 333
 334 #ifdef CONFIG_SG_POOL
 335 void sg_free_table_chained(struct sg_table *table,
 336                            unsigned nents_first_chunk);
 337 int sg_alloc_table_chained(struct sg_table *table, int nents,
 338                            struct scatterlist *first_chunk,
 339                            unsigned nents_first_chunk);
 340 #endif
 341
 342 /*
 343  * sg page iterator
 344  *
 345  * Iterates over sg entries page-by-page.  On each successful iteration, you
 346  * can call sg_page_iter_page(@piter) to get the current page.
 347  * @piter->sg will point to the sg holding this page and @piter->sg_pgoffset to
 348  * the page's page offset within the sg. The iteration will stop either when a
 349  * maximum number of sg entries was reached or a terminating sg
 350  * (sg_last(sg) == true) was reached.
 351  */
 352 struct sg_page_iter {
 353         struct scatterlist      *sg;            /* sg holding the page */
 354         unsigned int            sg_pgoffset;    /* page offset within the sg */
 355
 356         /* these are internal states, keep away */
 357         unsigned int            __nents;        /* remaining sg entries */
 358         int                     __pg_advance;   /* nr pages to advance at the
 359                                                  * next step */
 360 };
 361
 362 /*
 363  * sg page iterator for DMA addresses
 364  *
 365  * This is the same as sg_page_iter however you can call
 366  * sg_page_iter_dma_address(@dma_iter) to get the page's DMA
 367  * address. sg_page_iter_page() cannot be called on this iterator.
 368  */
 369 struct sg_dma_page_iter {
 370         struct sg_page_iter base;
 371 };
 372
 373 bool __sg_page_iter_next(struct sg_page_iter *piter);
 374 bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter);
 375 void __sg_page_iter_start(struct sg_page_iter *piter,
 376                           struct scatterlist *sglist, unsigned int nents,
 377                           unsigned long pgoffset);
 378 /**
 379  * sg_page_iter_page - get the current page held by the page iterator
 380  * @piter:      page iterator holding the page
 381  */
 382 static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
 383 {
 384         return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
 385 }
 386
 387 /**
 388  * sg_page_iter_dma_address - get the dma address of the current page held by
 389  * the page iterator.
 390  * @dma_iter:   page iterator holding the page
 391  */
 392 static inline dma_addr_t
 393 sg_page_iter_dma_address(struct sg_dma_page_iter *dma_iter)
 394 {
 395         return sg_dma_address(dma_iter->base.sg) +
 396                (dma_iter->base.sg_pgoffset << PAGE_SHIFT);
 397 }
 398
 399 /**
 400  * for_each_sg_page - iterate over the pages of the given sg list
 401  * @sglist:     sglist to iterate over
 402  * @piter:      page iterator to hold current page, sg, sg_pgoffset
 403  * @nents:      maximum number of sg entries to iterate over
 404  * @pgoffset:   starting page offset
 405  *
 406  * Callers may use sg_page_iter_page() to get each page pointer.
 407  */
 408 #define for_each_sg_page(sglist, piter, nents, pgoffset)                   \
 409         for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
 410              __sg_page_iter_next(piter);)
 411
 412 /**
 413  * for_each_sg_dma_page - iterate over the pages of the given sg list
 414  * @sglist:     sglist to iterate over
 415  * @dma_iter:   page iterator to hold current page
 416  * @dma_nents:  maximum number of sg entries to iterate over, this is the value
 417  *              returned from dma_map_sg
 418  * @pgoffset:   starting page offset
 419  *
 420  * Callers may use sg_page_iter_dma_address() to get each page's DMA address.
 421  */
 422 #define for_each_sg_dma_page(sglist, dma_iter, dma_nents, pgoffset)            \
 423         for (__sg_page_iter_start(&(dma_iter)->base, sglist, dma_nents,        \
 424                                   pgoffset);                                   \
 425              __sg_page_iter_dma_next(dma_iter);)
 426
 427 /*
 428  * Mapping sg iterator
 429  *
 430  * Iterates over sg entries mapping page-by-page.  On each successful
 431  * iteration, @miter->page points to the mapped page and
 432  * @miter->length bytes of data can be accessed at @miter->addr.  As
 433  * long as an interation is enclosed between start and stop, the user
 434  * is free to choose control structure and when to stop.
 435  *
 436  * @miter->consumed is set to @miter->length on each iteration.  It
 437  * can be adjusted if the user can't consume all the bytes in one go.
 438  * Also, a stopped iteration can be resumed by calling next on it.
 439  * This is useful when iteration needs to release all resources and
 440  * continue later (e.g. at the next interrupt).
 441  */
 442
 443 #define SG_MITER_ATOMIC         (1 << 0)         /* use kmap_atomic */
 444 #define SG_MITER_TO_SG          (1 << 1)        /* flush back to phys on unmap */
 445 #define SG_MITER_FROM_SG        (1 << 2)        /* nop */
 446
 447 struct sg_mapping_iter {
 448         /* the following three fields can be accessed directly */
 449         struct page             *page;          /* currently mapped page */
 450         void                    *addr;          /* pointer to the mapped area */
 451         size_t                  length;         /* length of the mapped area */
 452         size_t                  consumed;       /* number of consumed bytes */
 453         struct sg_page_iter     piter;          /* page iterator */
 454
 455         /* these are internal states, keep away */
 456         unsigned int            __offset;       /* offset within page */
 457         unsigned int            __remaining;    /* remaining bytes on page */
 458         unsigned int            __flags;
 459 };
 460
 461 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
 462                     unsigned int nents, unsigned int flags);
 463 bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
 464 bool sg_miter_next(struct sg_mapping_iter *miter);
 465 void sg_miter_stop(struct sg_mapping_iter *miter);
 466
 467 #endif /* _LINUX_SCATTERLIST_H */