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 #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  * Since the above length field is an unsigned int, below we define the maximum
  26  * length in bytes that can be stored in one scatterlist entry.
  27  */
  28 #define SCATTERLIST_MAX_SEGMENT (UINT_MAX & PAGE_MASK)
  29
  30 /*
  31  * These macros should be used after a dma_map_sg call has been done
  32  * to get bus addresses of each of the SG entries and their lengths.
  33  * You should only work with the number of sg entries dma_map_sg
  34  * returns, or alternatively stop on the first sg_dma_len(sg) which
  35  * is 0.
  36  */
  37 #define sg_dma_address(sg)      ((sg)->dma_address)
  38
  39 #ifdef CONFIG_NEED_SG_DMA_LENGTH
  40 #define sg_dma_len(sg)          ((sg)->dma_length)
  41 #else
  42 #define sg_dma_len(sg)          ((sg)->length)
  43 #endif
  44
  45 struct sg_table {
  46         struct scatterlist *sgl;        /* the list */
  47         unsigned int nents;             /* number of mapped entries */
  48         unsigned int orig_nents;        /* original size of list */
  49 };
  50
  51 /*
  52  * Notes on SG table design.
  53  *
  54  * We use the unsigned long page_link field in the scatterlist struct to place
  55  * the page pointer AND encode information about the sg table as well. The two
  56  * lower bits are reserved for this information.
  57  *
  58  * If bit 0 is set, then the page_link contains a pointer to the next sg
  59  * table list. Otherwise the next entry is at sg + 1.
  60  *
  61  * If bit 1 is set, then this sg entry is the last element in a list.
  62  *
  63  * See sg_next().
  64  *
  65  */
  66
  67 #define SG_MAGIC        0x87654321
  68
  69 /*
  70  * We overload the LSB of the page pointer to indicate whether it's
  71  * a valid sg entry, or whether it points to the start of a new scatterlist.
  72  * Those low bits are there for everyone! (thanks mason :-)
  73  */
  74 #define sg_is_chain(sg)         ((sg)->page_link & 0x01)
  75 #define sg_is_last(sg)          ((sg)->page_link & 0x02)
  76 #define sg_chain_ptr(sg)        \
  77         ((struct scatterlist *) ((sg)->page_link & ~0x03))
  78
  79 /**
  80  * sg_assign_page - Assign a given page to an SG entry
  81  * @sg:             SG entry
  82  * @page:           The page
  83  *
  84  * Description:
  85  *   Assign page to sg entry. Also see sg_set_page(), the most commonly used
  86  *   variant.
  87  *
  88  **/
  89 static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
  90 {
  91         unsigned long page_link = sg->page_link & 0x3;
  92
  93         /*
  94          * In order for the low bit stealing approach to work, pages
  95          * must be aligned at a 32-bit boundary as a minimum.
  96          */
  97         BUG_ON((unsigned long) page & 0x03);
  98 #ifdef CONFIG_DEBUG_SG
  99         BUG_ON(sg->sg_magic != SG_MAGIC);
 100         BUG_ON(sg_is_chain(sg));
 101 #endif
 102         sg->page_link = page_link | (unsigned long) page;
 103 }
 104
 105 /**
 106  * sg_set_page - Set sg entry to point at given page
 107  * @sg:          SG entry
 108  * @page:        The page
 109  * @len:         Length of data
 110  * @offset:      Offset into page
 111  *
 112  * Description:
 113  *   Use this function to set an sg entry pointing at a page, never assign
 114  *   the page directly. We encode sg table information in the lower bits
 115  *   of the page pointer. See sg_page() for looking up the page belonging
 116  *   to an sg entry.
 117  *
 118  **/
 119 static inline void sg_set_page(struct scatterlist *sg, struct page *page,
 120                                unsigned int len, unsigned int offset)
 121 {
 122         sg_assign_page(sg, page);
 123         sg->offset = offset;
 124         sg->length = len;
 125 }
 126
 127 static inline struct page *sg_page(struct scatterlist *sg)
 128 {
 129 #ifdef CONFIG_DEBUG_SG
 130         BUG_ON(sg->sg_magic != SG_MAGIC);
 131         BUG_ON(sg_is_chain(sg));
 132 #endif
 133         return (struct page *)((sg)->page_link & ~0x3);
 134 }
 135
 136 /**
 137  * sg_set_buf - Set sg entry to point at given data
 138  * @sg:          SG entry
 139  * @buf:         Data
 140  * @buflen:      Data length
 141  *
 142  **/
 143 static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
 144                               unsigned int buflen)
 145 {
 146 #ifdef CONFIG_DEBUG_SG
 147         BUG_ON(!virt_addr_valid(buf));
 148 #endif
 149         sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
 150 }
 151
 152 /*
 153  * Loop over each sg element, following the pointer to a new list if necessary
 154  */
 155 #define for_each_sg(sglist, sg, nr, __i)        \
 156         for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
 157
 158 /**
 159  * sg_chain - Chain two sglists together
 160  * @prv:        First scatterlist
 161  * @prv_nents:  Number of entries in prv
 162  * @sgl:        Second scatterlist
 163  *
 164  * Description:
 165  *   Links @prv@ and @sgl@ together, to form a longer scatterlist.
 166  *
 167  **/
 168 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
 169                             struct scatterlist *sgl)
 170 {
 171         /*
 172          * offset and length are unused for chain entry.  Clear them.
 173          */
 174         prv[prv_nents - 1].offset = 0;
 175         prv[prv_nents - 1].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         prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
 182 }
 183
 184 /**
 185  * sg_mark_end - Mark the end of the scatterlist
 186  * @sg:          SG entryScatterlist
 187  *
 188  * Description:
 189  *   Marks the passed in sg entry as the termination point for the sg
 190  *   table. A call to sg_next() on this entry will return NULL.
 191  *
 192  **/
 193 static inline void sg_mark_end(struct scatterlist *sg)
 194 {
 195 #ifdef CONFIG_DEBUG_SG
 196         BUG_ON(sg->sg_magic != SG_MAGIC);
 197 #endif
 198         /*
 199          * Set termination bit, clear potential chain bit
 200          */
 201         sg->page_link |= 0x02;
 202         sg->page_link &= ~0x01;
 203 }
 204
 205 /**
 206  * sg_unmark_end - Undo setting the end of the scatterlist
 207  * @sg:          SG entryScatterlist
 208  *
 209  * Description:
 210  *   Removes the termination marker from the given entry of the scatterlist.
 211  *
 212  **/
 213 static inline void sg_unmark_end(struct scatterlist *sg)
 214 {
 215 #ifdef CONFIG_DEBUG_SG
 216         BUG_ON(sg->sg_magic != SG_MAGIC);
 217 #endif
 218         sg->page_link &= ~0x02;
 219 }
 220
 221 /**
 222  * sg_phys - Return physical address of an sg entry
 223  * @sg:      SG entry
 224  *
 225  * Description:
 226  *   This calls page_to_phys() on the page in this sg entry, and adds the
 227  *   sg offset. The caller must know that it is legal to call page_to_phys()
 228  *   on the sg page.
 229  *
 230  **/
 231 static inline dma_addr_t sg_phys(struct scatterlist *sg)
 232 {
 233         return page_to_phys(sg_page(sg)) + sg->offset;
 234 }
 235
 236 /**
 237  * sg_virt - Return virtual address of an sg entry
 238  * @sg:      SG entry
 239  *
 240  * Description:
 241  *   This calls page_address() on the page in this sg entry, and adds the
 242  *   sg offset. The caller must know that the sg page has a valid virtual
 243  *   mapping.
 244  *
 245  **/
 246 static inline void *sg_virt(struct scatterlist *sg)
 247 {
 248         return page_address(sg_page(sg)) + sg->offset;
 249 }
 250
 251 int sg_nents(struct scatterlist *sg);
 252 int sg_nents_for_len(struct scatterlist *sg, u64 len);
 253 struct scatterlist *sg_next(struct scatterlist *);
 254 struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
 255 void sg_init_table(struct scatterlist *, unsigned int);
 256 void sg_init_one(struct scatterlist *, const void *, unsigned int);
 257 int sg_split(struct scatterlist *in, const int in_mapped_nents,
 258              const off_t skip, const int nb_splits,
 259              const size_t *split_sizes,
 260              struct scatterlist **out, int *out_mapped_nents,
 261              gfp_t gfp_mask);
 262
 263 typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
 264 typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
 265
 266 void __sg_free_table(struct sg_table *, unsigned int, bool, sg_free_fn *);
 267 void sg_free_table(struct sg_table *);
 268 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
 269                      struct scatterlist *, gfp_t, sg_alloc_fn *);
 270 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
 271 int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
 272                                 unsigned int n_pages, unsigned int offset,
 273                                 unsigned long size, unsigned int max_segment,
 274                                 gfp_t gfp_mask);
 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, gfp_t gfp_mask);
 278
 279 #ifdef CONFIG_SGL_ALLOC
 280 struct scatterlist *sgl_alloc_order(unsigned long long length,
 281                                     unsigned int order, bool chainable,
 282                                     gfp_t gfp, unsigned int *nent_p);
 283 struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
 284                               unsigned int *nent_p);
 285 void sgl_free_order(struct scatterlist *sgl, int order);
 286 void sgl_free(struct scatterlist *sgl);
 287 #endif /* CONFIG_SGL_ALLOC */
 288
 289 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
 290                       size_t buflen, off_t skip, bool to_buffer);
 291
 292 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 293                            const void *buf, size_t buflen);
 294 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 295                          void *buf, size_t buflen);
 296
 297 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 298                             const void *buf, size_t buflen, off_t skip);
 299 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 300                           void *buf, size_t buflen, off_t skip);
 301 size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
 302                        size_t buflen, off_t skip);
 303
 304 /*
 305  * Maximum number of entries that will be allocated in one piece, if
 306  * a list larger than this is required then chaining will be utilized.
 307  */
 308 #define SG_MAX_SINGLE_ALLOC             (PAGE_SIZE / sizeof(struct scatterlist))
 309
 310 /*
 311  * The maximum number of SG segments that we will put inside a
 312  * scatterlist (unless chaining is used). Should ideally fit inside a
 313  * single page, to avoid a higher order allocation.  We could define this
 314  * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order.  The
 315  * minimum value is 32
 316  */
 317 #define SG_CHUNK_SIZE   128
 318
 319 /*
 320  * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
 321  * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
 322  */
 323 #ifdef CONFIG_ARCH_HAS_SG_CHAIN
 324 #define SG_MAX_SEGMENTS 2048
 325 #else
 326 #define SG_MAX_SEGMENTS SG_CHUNK_SIZE
 327 #endif
 328
 329 #ifdef CONFIG_SG_POOL
 330 void sg_free_table_chained(struct sg_table *table, bool first_chunk);
 331 int sg_alloc_table_chained(struct sg_table *table, int nents,
 332                            struct scatterlist *first_chunk);
 333 #endif
 334
 335 /*
 336  * sg page iterator
 337  *
 338  * Iterates over sg entries page-by-page.  On each successful iteration,
 339  * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
 340  * to get the current page and its dma address. @piter->sg will point to the
 341  * sg holding this page and @piter->sg_pgoffset to the page's page offset
 342  * within the sg. The iteration will stop either when a maximum number of sg
 343  * entries was reached or a terminating sg (sg_last(sg) == true) was reached.
 344  */
 345 struct sg_page_iter {
 346         struct scatterlist      *sg;            /* sg holding the page */
 347         unsigned int            sg_pgoffset;    /* page offset within the sg */
 348
 349         /* these are internal states, keep away */
 350         unsigned int            __nents;        /* remaining sg entries */
 351         int                     __pg_advance;   /* nr pages to advance at the
 352                                                  * next step */
 353 };
 354
 355 bool __sg_page_iter_next(struct sg_page_iter *piter);
 356 void __sg_page_iter_start(struct sg_page_iter *piter,
 357                           struct scatterlist *sglist, unsigned int nents,
 358                           unsigned long pgoffset);
 359 /**
 360  * sg_page_iter_page - get the current page held by the page iterator
 361  * @piter:      page iterator holding the page
 362  */
 363 static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
 364 {
 365         return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
 366 }
 367
 368 /**
 369  * sg_page_iter_dma_address - get the dma address of the current page held by
 370  * the page iterator.
 371  * @piter:      page iterator holding the page
 372  */
 373 static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter)
 374 {
 375         return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT);
 376 }
 377
 378 /**
 379  * for_each_sg_page - iterate over the pages of the given sg list
 380  * @sglist:     sglist to iterate over
 381  * @piter:      page iterator to hold current page, sg, sg_pgoffset
 382  * @nents:      maximum number of sg entries to iterate over
 383  * @pgoffset:   starting page offset
 384  */
 385 #define for_each_sg_page(sglist, piter, nents, pgoffset)                   \
 386         for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
 387              __sg_page_iter_next(piter);)
 388
 389 /*
 390  * Mapping sg iterator
 391  *
 392  * Iterates over sg entries mapping page-by-page.  On each successful
 393  * iteration, @miter->page points to the mapped page and
 394  * @miter->length bytes of data can be accessed at @miter->addr.  As
 395  * long as an interation is enclosed between start and stop, the user
 396  * is free to choose control structure and when to stop.
 397  *
 398  * @miter->consumed is set to @miter->length on each iteration.  It
 399  * can be adjusted if the user can't consume all the bytes in one go.
 400  * Also, a stopped iteration can be resumed by calling next on it.
 401  * This is useful when iteration needs to release all resources and
 402  * continue later (e.g. at the next interrupt).
 403  */
 404
 405 #define SG_MITER_ATOMIC         (1 << 0)         /* use kmap_atomic */
 406 #define SG_MITER_TO_SG          (1 << 1)        /* flush back to phys on unmap */
 407 #define SG_MITER_FROM_SG        (1 << 2)        /* nop */
 408
 409 struct sg_mapping_iter {
 410         /* the following three fields can be accessed directly */
 411         struct page             *page;          /* currently mapped page */
 412         void                    *addr;          /* pointer to the mapped area */
 413         size_t                  length;         /* length of the mapped area */
 414         size_t                  consumed;       /* number of consumed bytes */
 415         struct sg_page_iter     piter;          /* page iterator */
 416
 417         /* these are internal states, keep away */
 418         unsigned int            __offset;       /* offset within page */
 419         unsigned int            __remaining;    /* remaining bytes on page */
 420         unsigned int            __flags;
 421 };
 422
 423 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
 424                     unsigned int nents, unsigned int flags);
 425 bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
 426 bool sg_miter_next(struct sg_mapping_iter *miter);
 427 void sg_miter_stop(struct sg_mapping_iter *miter);
 428
 429 #endif /* _LINUX_SCATTERLIST_H */