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, bool, sg_free_fn *);
 270 void sg_free_table(struct sg_table *);
 271 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
 272                      struct scatterlist *, gfp_t, sg_alloc_fn *);
 273 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
 274 int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
 275                                 unsigned int n_pages, unsigned int offset,
 276                                 unsigned long size, unsigned int max_segment,
 277                                 gfp_t gfp_mask);
 278 int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
 279                               unsigned int n_pages, unsigned int offset,
 280                               unsigned long size, gfp_t gfp_mask);
 281
 282 #ifdef CONFIG_SGL_ALLOC
 283 struct scatterlist *sgl_alloc_order(unsigned long long length,
 284                                     unsigned int order, bool chainable,
 285                                     gfp_t gfp, unsigned int *nent_p);
 286 struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
 287                               unsigned int *nent_p);
 288 void sgl_free_n_order(struct scatterlist *sgl, int nents, int order);
 289 void sgl_free_order(struct scatterlist *sgl, int order);
 290 void sgl_free(struct scatterlist *sgl);
 291 #endif /* CONFIG_SGL_ALLOC */
 292
 293 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
 294                       size_t buflen, off_t skip, bool to_buffer);
 295
 296 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 297                            const void *buf, size_t buflen);
 298 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 299                          void *buf, size_t buflen);
 300
 301 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 302                             const void *buf, size_t buflen, off_t skip);
 303 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 304                           void *buf, size_t buflen, off_t skip);
 305 size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
 306                        size_t buflen, off_t skip);
 307
 308 /*
 309  * Maximum number of entries that will be allocated in one piece, if
 310  * a list larger than this is required then chaining will be utilized.
 311  */
 312 #define SG_MAX_SINGLE_ALLOC             (PAGE_SIZE / sizeof(struct scatterlist))
 313
 314 /*
 315  * The maximum number of SG segments that we will put inside a
 316  * scatterlist (unless chaining is used). Should ideally fit inside a
 317  * single page, to avoid a higher order allocation.  We could define this
 318  * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order.  The
 319  * minimum value is 32
 320  */
 321 #define SG_CHUNK_SIZE   128
 322
 323 /*
 324  * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
 325  * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
 326  */
 327 #ifdef CONFIG_ARCH_HAS_SG_CHAIN
 328 #define SG_MAX_SEGMENTS 2048
 329 #else
 330 #define SG_MAX_SEGMENTS SG_CHUNK_SIZE
 331 #endif
 332
 333 #ifdef CONFIG_SG_POOL
 334 void sg_free_table_chained(struct sg_table *table, bool first_chunk);
 335 int sg_alloc_table_chained(struct sg_table *table, int nents,
 336                            struct scatterlist *first_chunk);
 337 #endif
 338
 339 /*
 340  * sg page iterator
 341  *
 342  * Iterates over sg entries page-by-page.  On each successful iteration,
 343  * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
 344  * to get the current page and its dma address. @piter->sg will point to the
 345  * sg holding this page and @piter->sg_pgoffset to the page's page offset
 346  * within the sg. The iteration will stop either when a maximum number of sg
 347  * entries was reached or a terminating sg (sg_last(sg) == true) was reached.
 348  */
 349 struct sg_page_iter {
 350         struct scatterlist      *sg;            /* sg holding the page */
 351         unsigned int            sg_pgoffset;    /* page offset within the sg */
 352
 353         /* these are internal states, keep away */
 354         unsigned int            __nents;        /* remaining sg entries */
 355         int                     __pg_advance;   /* nr pages to advance at the
 356                                                  * next step */
 357 };
 358
 359 bool __sg_page_iter_next(struct sg_page_iter *piter);
 360 void __sg_page_iter_start(struct sg_page_iter *piter,
 361                           struct scatterlist *sglist, unsigned int nents,
 362                           unsigned long pgoffset);
 363 /**
 364  * sg_page_iter_page - get the current page held by the page iterator
 365  * @piter:      page iterator holding the page
 366  */
 367 static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
 368 {
 369         return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
 370 }
 371
 372 /**
 373  * sg_page_iter_dma_address - get the dma address of the current page held by
 374  * the page iterator.
 375  * @piter:      page iterator holding the page
 376  */
 377 static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter)
 378 {
 379         return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT);
 380 }
 381
 382 /**
 383  * for_each_sg_page - iterate over the pages of the given sg list
 384  * @sglist:     sglist to iterate over
 385  * @piter:      page iterator to hold current page, sg, sg_pgoffset
 386  * @nents:      maximum number of sg entries to iterate over
 387  * @pgoffset:   starting page offset
 388  */
 389 #define for_each_sg_page(sglist, piter, nents, pgoffset)                   \
 390         for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
 391              __sg_page_iter_next(piter);)
 392
 393 /*
 394  * Mapping sg iterator
 395  *
 396  * Iterates over sg entries mapping page-by-page.  On each successful
 397  * iteration, @miter->page points to the mapped page and
 398  * @miter->length bytes of data can be accessed at @miter->addr.  As
 399  * long as an interation is enclosed between start and stop, the user
 400  * is free to choose control structure and when to stop.
 401  *
 402  * @miter->consumed is set to @miter->length on each iteration.  It
 403  * can be adjusted if the user can't consume all the bytes in one go.
 404  * Also, a stopped iteration can be resumed by calling next on it.
 405  * This is useful when iteration needs to release all resources and
 406  * continue later (e.g. at the next interrupt).
 407  */
 408
 409 #define SG_MITER_ATOMIC         (1 << 0)         /* use kmap_atomic */
 410 #define SG_MITER_TO_SG          (1 << 1)        /* flush back to phys on unmap */
 411 #define SG_MITER_FROM_SG        (1 << 2)        /* nop */
 412
 413 struct sg_mapping_iter {
 414         /* the following three fields can be accessed directly */
 415         struct page             *page;          /* currently mapped page */
 416         void                    *addr;          /* pointer to the mapped area */
 417         size_t                  length;         /* length of the mapped area */
 418         size_t                  consumed;       /* number of consumed bytes */
 419         struct sg_page_iter     piter;          /* page iterator */
 420
 421         /* these are internal states, keep away */
 422         unsigned int            __offset;       /* offset within page */
 423         unsigned int            __remaining;    /* remaining bytes on page */
 424         unsigned int            __flags;
 425 };
 426
 427 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
 428                     unsigned int nents, unsigned int flags);
 429 bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
 430 bool sg_miter_next(struct sg_mapping_iter *miter);
 431 void sg_miter_stop(struct sg_mapping_iter *miter);
 432
 433 #endif /* _LINUX_SCATTERLIST_H */