include/linux/scatterlist.h

   1 #ifndef _LINUX_SCATTERLIST_H
   2 #define _LINUX_SCATTERLIST_H
   3
   4 #include <linux/string.h>
   5 #include <linux/types.h>
   6 #include <linux/bug.h>
   7 #include <linux/mm.h>
   8 #include <asm/io.h>
   9
  10 struct scatterlist {
  11 #ifdef CONFIG_DEBUG_SG
  12         unsigned long   sg_magic;
  13 #endif
  14         unsigned long   page_link;
  15         unsigned int    offset;
  16         unsigned int    length;
  17         dma_addr_t      dma_address;
  18 #ifdef CONFIG_NEED_SG_DMA_LENGTH
  19         unsigned int    dma_length;
  20 #endif
  21 };
  22
  23 /*
  24  * Since the above length field is an unsigned int, below we define the maximum
  25  * length in bytes that can be stored in one scatterlist entry.
  26  */
  27 #define SCATTERLIST_MAX_SEGMENT (UINT_MAX & PAGE_MASK)
  28
  29 /*
  30  * These macros should be used after a dma_map_sg call has been done
  31  * to get bus addresses of each of the SG entries and their lengths.
  32  * You should only work with the number of sg entries dma_map_sg
  33  * returns, or alternatively stop on the first sg_dma_len(sg) which
  34  * is 0.
  35  */
  36 #define sg_dma_address(sg)      ((sg)->dma_address)
  37
  38 #ifdef CONFIG_NEED_SG_DMA_LENGTH
  39 #define sg_dma_len(sg)          ((sg)->dma_length)
  40 #else
  41 #define sg_dma_len(sg)          ((sg)->length)
  42 #endif
  43
  44 struct sg_table {
  45         struct scatterlist *sgl;        /* the list */
  46         unsigned int nents;             /* number of mapped entries */
  47         unsigned int orig_nents;        /* original size of list */
  48 };
  49
  50 /*
  51  * Notes on SG table design.
  52  *
  53  * We use the unsigned long page_link field in the scatterlist struct to place
  54  * the page pointer AND encode information about the sg table as well. The two
  55  * lower bits are reserved for this information.
  56  *
  57  * If bit 0 is set, then the page_link contains a pointer to the next sg
  58  * table list. Otherwise the next entry is at sg + 1.
  59  *
  60  * If bit 1 is set, then this sg entry is the last element in a list.
  61  *
  62  * See sg_next().
  63  *
  64  */
  65
  66 #define SG_MAGIC        0x87654321
  67
  68 /*
  69  * We overload the LSB of the page pointer to indicate whether it's
  70  * a valid sg entry, or whether it points to the start of a new scatterlist.
  71  * Those low bits are there for everyone! (thanks mason :-)
  72  */
  73 #define sg_is_chain(sg)         ((sg)->page_link & 0x01)
  74 #define sg_is_last(sg)          ((sg)->page_link & 0x02)
  75 #define sg_chain_ptr(sg)        \
  76         ((struct scatterlist *) ((sg)->page_link & ~0x03))
  77
  78 /**
  79  * sg_assign_page - Assign a given page to an SG entry
  80  * @sg:             SG entry
  81  * @page:           The page
  82  *
  83  * Description:
  84  *   Assign page to sg entry. Also see sg_set_page(), the most commonly used
  85  *   variant.
  86  *
  87  **/
  88 static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
  89 {
  90         unsigned long page_link = sg->page_link & 0x3;
  91
  92         /*
  93          * In order for the low bit stealing approach to work, pages
  94          * must be aligned at a 32-bit boundary as a minimum.
  95          */
  96         BUG_ON((unsigned long) page & 0x03);
  97 #ifdef CONFIG_DEBUG_SG
  98         BUG_ON(sg->sg_magic != SG_MAGIC);
  99         BUG_ON(sg_is_chain(sg));
 100 #endif
 101         sg->page_link = page_link | (unsigned long) page;
 102 }
 103
 104 /**
 105  * sg_set_page - Set sg entry to point at given page
 106  * @sg:          SG entry
 107  * @page:        The page
 108  * @len:         Length of data
 109  * @offset:      Offset into page
 110  *
 111  * Description:
 112  *   Use this function to set an sg entry pointing at a page, never assign
 113  *   the page directly. We encode sg table information in the lower bits
 114  *   of the page pointer. See sg_page() for looking up the page belonging
 115  *   to an sg entry.
 116  *
 117  **/
 118 static inline void sg_set_page(struct scatterlist *sg, struct page *page,
 119                                unsigned int len, unsigned int offset)
 120 {
 121         sg_assign_page(sg, page);
 122         sg->offset = offset;
 123         sg->length = len;
 124 }
 125
 126 static inline struct page *sg_page(struct scatterlist *sg)
 127 {
 128 #ifdef CONFIG_DEBUG_SG
 129         BUG_ON(sg->sg_magic != SG_MAGIC);
 130         BUG_ON(sg_is_chain(sg));
 131 #endif
 132         return (struct page *)((sg)->page_link & ~0x3);
 133 }
 134
 135 /**
 136  * sg_set_buf - Set sg entry to point at given data
 137  * @sg:          SG entry
 138  * @buf:         Data
 139  * @buflen:      Data length
 140  *
 141  **/
 142 static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
 143                               unsigned int buflen)
 144 {
 145 #ifdef CONFIG_DEBUG_SG
 146         BUG_ON(!virt_addr_valid(buf));
 147 #endif
 148         sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
 149 }
 150
 151 /*
 152  * Loop over each sg element, following the pointer to a new list if necessary
 153  */
 154 #define for_each_sg(sglist, sg, nr, __i)        \
 155         for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
 156
 157 /**
 158  * sg_chain - Chain two sglists together
 159  * @prv:        First scatterlist
 160  * @prv_nents:  Number of entries in prv
 161  * @sgl:        Second scatterlist
 162  *
 163  * Description:
 164  *   Links @prv@ and @sgl@ together, to form a longer scatterlist.
 165  *
 166  **/
 167 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
 168                             struct scatterlist *sgl)
 169 {
 170         /*
 171          * offset and length are unused for chain entry.  Clear them.
 172          */
 173         prv[prv_nents - 1].offset = 0;
 174         prv[prv_nents - 1].length = 0;
 175
 176         /*
 177          * Set lowest bit to indicate a link pointer, and make sure to clear
 178          * the termination bit if it happens to be set.
 179          */
 180         prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
 181 }
 182
 183 /**
 184  * sg_mark_end - Mark the end of the scatterlist
 185  * @sg:          SG entryScatterlist
 186  *
 187  * Description:
 188  *   Marks the passed in sg entry as the termination point for the sg
 189  *   table. A call to sg_next() on this entry will return NULL.
 190  *
 191  **/
 192 static inline void sg_mark_end(struct scatterlist *sg)
 193 {
 194 #ifdef CONFIG_DEBUG_SG
 195         BUG_ON(sg->sg_magic != SG_MAGIC);
 196 #endif
 197         /*
 198          * Set termination bit, clear potential chain bit
 199          */
 200         sg->page_link |= 0x02;
 201         sg->page_link &= ~0x01;
 202 }
 203
 204 /**
 205  * sg_unmark_end - Undo setting the end of the scatterlist
 206  * @sg:          SG entryScatterlist
 207  *
 208  * Description:
 209  *   Removes the termination marker from the given entry of the scatterlist.
 210  *
 211  **/
 212 static inline void sg_unmark_end(struct scatterlist *sg)
 213 {
 214 #ifdef CONFIG_DEBUG_SG
 215         BUG_ON(sg->sg_magic != SG_MAGIC);
 216 #endif
 217         sg->page_link &= ~0x02;
 218 }
 219
 220 /**
 221  * sg_phys - Return physical address of an sg entry
 222  * @sg:      SG entry
 223  *
 224  * Description:
 225  *   This calls page_to_phys() on the page in this sg entry, and adds the
 226  *   sg offset. The caller must know that it is legal to call page_to_phys()
 227  *   on the sg page.
 228  *
 229  **/
 230 static inline dma_addr_t sg_phys(struct scatterlist *sg)
 231 {
 232         return page_to_phys(sg_page(sg)) + sg->offset;
 233 }
 234
 235 /**
 236  * sg_virt - Return virtual address of an sg entry
 237  * @sg:      SG entry
 238  *
 239  * Description:
 240  *   This calls page_address() on the page in this sg entry, and adds the
 241  *   sg offset. The caller must know that the sg page has a valid virtual
 242  *   mapping.
 243  *
 244  **/
 245 static inline void *sg_virt(struct scatterlist *sg)
 246 {
 247         return page_address(sg_page(sg)) + sg->offset;
 248 }
 249
 250 int sg_nents(struct scatterlist *sg);
 251 int sg_nents_for_len(struct scatterlist *sg, u64 len);
 252 struct scatterlist *sg_next(struct scatterlist *);
 253 struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
 254 void sg_init_table(struct scatterlist *, unsigned int);
 255 void sg_init_one(struct scatterlist *, const void *, unsigned int);
 256 int sg_split(struct scatterlist *in, const int in_mapped_nents,
 257              const off_t skip, const int nb_splits,
 258              const size_t *split_sizes,
 259              struct scatterlist **out, int *out_mapped_nents,
 260              gfp_t gfp_mask);
 261
 262 typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
 263 typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
 264
 265 void __sg_free_table(struct sg_table *, unsigned int, bool, sg_free_fn *);
 266 void sg_free_table(struct sg_table *);
 267 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
 268                      struct scatterlist *, gfp_t, sg_alloc_fn *);
 269 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
 270 int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
 271                                 unsigned int n_pages, unsigned int offset,
 272                                 unsigned long size, unsigned int max_segment,
 273                                 gfp_t gfp_mask);
 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, gfp_t gfp_mask);
 277
 278 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
 279                       size_t buflen, off_t skip, bool to_buffer);
 280
 281 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 282                            const void *buf, size_t buflen);
 283 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 284                          void *buf, size_t buflen);
 285
 286 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 287                             const void *buf, size_t buflen, off_t skip);
 288 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 289                           void *buf, size_t buflen, off_t skip);
 290 size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
 291                        size_t buflen, off_t skip);
 292
 293 /*
 294  * Maximum number of entries that will be allocated in one piece, if
 295  * a list larger than this is required then chaining will be utilized.
 296  */
 297 #define SG_MAX_SINGLE_ALLOC             (PAGE_SIZE / sizeof(struct scatterlist))
 298
 299 /*
 300  * The maximum number of SG segments that we will put inside a
 301  * scatterlist (unless chaining is used). Should ideally fit inside a
 302  * single page, to avoid a higher order allocation.  We could define this
 303  * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order.  The
 304  * minimum value is 32
 305  */
 306 #define SG_CHUNK_SIZE   128
 307
 308 /*
 309  * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
 310  * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
 311  */
 312 #ifdef CONFIG_ARCH_HAS_SG_CHAIN
 313 #define SG_MAX_SEGMENTS 2048
 314 #else
 315 #define SG_MAX_SEGMENTS SG_CHUNK_SIZE
 316 #endif
 317
 318 #ifdef CONFIG_SG_POOL
 319 void sg_free_table_chained(struct sg_table *table, bool first_chunk);
 320 int sg_alloc_table_chained(struct sg_table *table, int nents,
 321                            struct scatterlist *first_chunk);
 322 #endif
 323
 324 /*
 325  * sg page iterator
 326  *
 327  * Iterates over sg entries page-by-page.  On each successful iteration,
 328  * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
 329  * to get the current page and its dma address. @piter->sg will point to the
 330  * sg holding this page and @piter->sg_pgoffset to the page's page offset
 331  * within the sg. The iteration will stop either when a maximum number of sg
 332  * entries was reached or a terminating sg (sg_last(sg) == true) was reached.
 333  */
 334 struct sg_page_iter {
 335         struct scatterlist      *sg;            /* sg holding the page */
 336         unsigned int            sg_pgoffset;    /* page offset within the sg */
 337
 338         /* these are internal states, keep away */
 339         unsigned int            __nents;        /* remaining sg entries */
 340         int                     __pg_advance;   /* nr pages to advance at the
 341                                                  * next step */
 342 };
 343
 344 bool __sg_page_iter_next(struct sg_page_iter *piter);
 345 void __sg_page_iter_start(struct sg_page_iter *piter,
 346                           struct scatterlist *sglist, unsigned int nents,
 347                           unsigned long pgoffset);
 348 /**
 349  * sg_page_iter_page - get the current page held by the page iterator
 350  * @piter:      page iterator holding the page
 351  */
 352 static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
 353 {
 354         return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
 355 }
 356
 357 /**
 358  * sg_page_iter_dma_address - get the dma address of the current page held by
 359  * the page iterator.
 360  * @piter:      page iterator holding the page
 361  */
 362 static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter)
 363 {
 364         return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT);
 365 }
 366
 367 /**
 368  * for_each_sg_page - iterate over the pages of the given sg list
 369  * @sglist:     sglist to iterate over
 370  * @piter:      page iterator to hold current page, sg, sg_pgoffset
 371  * @nents:      maximum number of sg entries to iterate over
 372  * @pgoffset:   starting page offset
 373  */
 374 #define for_each_sg_page(sglist, piter, nents, pgoffset)                   \
 375         for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
 376              __sg_page_iter_next(piter);)
 377
 378 /*
 379  * Mapping sg iterator
 380  *
 381  * Iterates over sg entries mapping page-by-page.  On each successful
 382  * iteration, @miter->page points to the mapped page and
 383  * @miter->length bytes of data can be accessed at @miter->addr.  As
 384  * long as an interation is enclosed between start and stop, the user
 385  * is free to choose control structure and when to stop.
 386  *
 387  * @miter->consumed is set to @miter->length on each iteration.  It
 388  * can be adjusted if the user can't consume all the bytes in one go.
 389  * Also, a stopped iteration can be resumed by calling next on it.
 390  * This is useful when iteration needs to release all resources and
 391  * continue later (e.g. at the next interrupt).
 392  */
 393
 394 #define SG_MITER_ATOMIC         (1 << 0)         /* use kmap_atomic */
 395 #define SG_MITER_TO_SG          (1 << 1)        /* flush back to phys on unmap */
 396 #define SG_MITER_FROM_SG        (1 << 2)        /* nop */
 397
 398 struct sg_mapping_iter {
 399         /* the following three fields can be accessed directly */
 400         struct page             *page;          /* currently mapped page */
 401         void                    *addr;          /* pointer to the mapped area */
 402         size_t                  length;         /* length of the mapped area */
 403         size_t                  consumed;       /* number of consumed bytes */
 404         struct sg_page_iter     piter;          /* page iterator */
 405
 406         /* these are internal states, keep away */
 407         unsigned int            __offset;       /* offset within page */
 408         unsigned int            __remaining;    /* remaining bytes on page */
 409         unsigned int            __flags;
 410 };
 411
 412 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
 413                     unsigned int nents, unsigned int flags);
 414 bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
 415 bool sg_miter_next(struct sg_mapping_iter *miter);
 416 void sg_miter_stop(struct sg_mapping_iter *miter);
 417
 418 #endif /* _LINUX_SCATTERLIST_H */