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  * These macros should be used after a dma_map_sg call has been done
  25  * to get bus addresses of each of the SG entries and their lengths.
  26  * You should only work with the number of sg entries dma_map_sg
  27  * returns, or alternatively stop on the first sg_dma_len(sg) which
  28  * is 0.
  29  */
  30 #define sg_dma_address(sg)      ((sg)->dma_address)
  31
  32 #ifdef CONFIG_NEED_SG_DMA_LENGTH
  33 #define sg_dma_len(sg)          ((sg)->dma_length)
  34 #else
  35 #define sg_dma_len(sg)          ((sg)->length)
  36 #endif
  37
  38 struct sg_table {
  39         struct scatterlist *sgl;        /* the list */
  40         unsigned int nents;             /* number of mapped entries */
  41         unsigned int orig_nents;        /* original size of list */
  42 };
  43
  44 /*
  45  * Notes on SG table design.
  46  *
  47  * We use the unsigned long page_link field in the scatterlist struct to place
  48  * the page pointer AND encode information about the sg table as well. The two
  49  * lower bits are reserved for this information.
  50  *
  51  * If bit 0 is set, then the page_link contains a pointer to the next sg
  52  * table list. Otherwise the next entry is at sg + 1.
  53  *
  54  * If bit 1 is set, then this sg entry is the last element in a list.
  55  *
  56  * See sg_next().
  57  *
  58  */
  59
  60 #define SG_MAGIC        0x87654321
  61
  62 /*
  63  * We overload the LSB of the page pointer to indicate whether it's
  64  * a valid sg entry, or whether it points to the start of a new scatterlist.
  65  * Those low bits are there for everyone! (thanks mason :-)
  66  */
  67 #define sg_is_chain(sg)         ((sg)->page_link & 0x01)
  68 #define sg_is_last(sg)          ((sg)->page_link & 0x02)
  69 #define sg_chain_ptr(sg)        \
  70         ((struct scatterlist *) ((sg)->page_link & ~0x03))
  71
  72 /**
  73  * sg_assign_page - Assign a given page to an SG entry
  74  * @sg:             SG entry
  75  * @page:           The page
  76  *
  77  * Description:
  78  *   Assign page to sg entry. Also see sg_set_page(), the most commonly used
  79  *   variant.
  80  *
  81  **/
  82 static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
  83 {
  84         unsigned long page_link = sg->page_link & 0x3;
  85
  86         /*
  87          * In order for the low bit stealing approach to work, pages
  88          * must be aligned at a 32-bit boundary as a minimum.
  89          */
  90         BUG_ON((unsigned long) page & 0x03);
  91 #ifdef CONFIG_DEBUG_SG
  92         BUG_ON(sg->sg_magic != SG_MAGIC);
  93         BUG_ON(sg_is_chain(sg));
  94 #endif
  95         sg->page_link = page_link | (unsigned long) page;
  96 }
  97
  98 /**
  99  * sg_set_page - Set sg entry to point at given page
 100  * @sg:          SG entry
 101  * @page:        The page
 102  * @len:         Length of data
 103  * @offset:      Offset into page
 104  *
 105  * Description:
 106  *   Use this function to set an sg entry pointing at a page, never assign
 107  *   the page directly. We encode sg table information in the lower bits
 108  *   of the page pointer. See sg_page() for looking up the page belonging
 109  *   to an sg entry.
 110  *
 111  **/
 112 static inline void sg_set_page(struct scatterlist *sg, struct page *page,
 113                                unsigned int len, unsigned int offset)
 114 {
 115         sg_assign_page(sg, page);
 116         sg->offset = offset;
 117         sg->length = len;
 118 }
 119
 120 static inline struct page *sg_page(struct scatterlist *sg)
 121 {
 122 #ifdef CONFIG_DEBUG_SG
 123         BUG_ON(sg->sg_magic != SG_MAGIC);
 124         BUG_ON(sg_is_chain(sg));
 125 #endif
 126         return (struct page *)((sg)->page_link & ~0x3);
 127 }
 128
 129 /**
 130  * sg_set_buf - Set sg entry to point at given data
 131  * @sg:          SG entry
 132  * @buf:         Data
 133  * @buflen:      Data length
 134  *
 135  **/
 136 static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
 137                               unsigned int buflen)
 138 {
 139 #ifdef CONFIG_DEBUG_SG
 140         BUG_ON(!virt_addr_valid(buf));
 141 #endif
 142         sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
 143 }
 144
 145 /*
 146  * Loop over each sg element, following the pointer to a new list if necessary
 147  */
 148 #define for_each_sg(sglist, sg, nr, __i)        \
 149         for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
 150
 151 /**
 152  * sg_chain - Chain two sglists together
 153  * @prv:        First scatterlist
 154  * @prv_nents:  Number of entries in prv
 155  * @sgl:        Second scatterlist
 156  *
 157  * Description:
 158  *   Links @prv@ and @sgl@ together, to form a longer scatterlist.
 159  *
 160  **/
 161 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
 162                             struct scatterlist *sgl)
 163 {
 164         /*
 165          * offset and length are unused for chain entry.  Clear them.
 166          */
 167         prv[prv_nents - 1].offset = 0;
 168         prv[prv_nents - 1].length = 0;
 169
 170         /*
 171          * Set lowest bit to indicate a link pointer, and make sure to clear
 172          * the termination bit if it happens to be set.
 173          */
 174         prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
 175 }
 176
 177 /**
 178  * sg_mark_end - Mark the end of the scatterlist
 179  * @sg:          SG entryScatterlist
 180  *
 181  * Description:
 182  *   Marks the passed in sg entry as the termination point for the sg
 183  *   table. A call to sg_next() on this entry will return NULL.
 184  *
 185  **/
 186 static inline void sg_mark_end(struct scatterlist *sg)
 187 {
 188 #ifdef CONFIG_DEBUG_SG
 189         BUG_ON(sg->sg_magic != SG_MAGIC);
 190 #endif
 191         /*
 192          * Set termination bit, clear potential chain bit
 193          */
 194         sg->page_link |= 0x02;
 195         sg->page_link &= ~0x01;
 196 }
 197
 198 /**
 199  * sg_unmark_end - Undo setting the end of the scatterlist
 200  * @sg:          SG entryScatterlist
 201  *
 202  * Description:
 203  *   Removes the termination marker from the given entry of the scatterlist.
 204  *
 205  **/
 206 static inline void sg_unmark_end(struct scatterlist *sg)
 207 {
 208 #ifdef CONFIG_DEBUG_SG
 209         BUG_ON(sg->sg_magic != SG_MAGIC);
 210 #endif
 211         sg->page_link &= ~0x02;
 212 }
 213
 214 /**
 215  * sg_phys - Return physical address of an sg entry
 216  * @sg:      SG entry
 217  *
 218  * Description:
 219  *   This calls page_to_phys() on the page in this sg entry, and adds the
 220  *   sg offset. The caller must know that it is legal to call page_to_phys()
 221  *   on the sg page.
 222  *
 223  **/
 224 static inline dma_addr_t sg_phys(struct scatterlist *sg)
 225 {
 226         return page_to_phys(sg_page(sg)) + sg->offset;
 227 }
 228
 229 /**
 230  * sg_virt - Return virtual address of an sg entry
 231  * @sg:      SG entry
 232  *
 233  * Description:
 234  *   This calls page_address() on the page in this sg entry, and adds the
 235  *   sg offset. The caller must know that the sg page has a valid virtual
 236  *   mapping.
 237  *
 238  **/
 239 static inline void *sg_virt(struct scatterlist *sg)
 240 {
 241         return page_address(sg_page(sg)) + sg->offset;
 242 }
 243
 244 int sg_nents(struct scatterlist *sg);
 245 int sg_nents_for_len(struct scatterlist *sg, u64 len);
 246 struct scatterlist *sg_next(struct scatterlist *);
 247 struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
 248 void sg_init_table(struct scatterlist *, unsigned int);
 249 void sg_init_one(struct scatterlist *, const void *, unsigned int);
 250 int sg_split(struct scatterlist *in, const int in_mapped_nents,
 251              const off_t skip, const int nb_splits,
 252              const size_t *split_sizes,
 253              struct scatterlist **out, int *out_mapped_nents,
 254              gfp_t gfp_mask);
 255
 256 typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
 257 typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
 258
 259 void __sg_free_table(struct sg_table *, unsigned int, bool, sg_free_fn *);
 260 void sg_free_table(struct sg_table *);
 261 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
 262                      struct scatterlist *, gfp_t, sg_alloc_fn *);
 263 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
 264 int sg_alloc_table_from_pages(struct sg_table *sgt,
 265         struct page **pages, unsigned int n_pages,
 266         unsigned long offset, unsigned long size,
 267         gfp_t gfp_mask);
 268
 269 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
 270                       size_t buflen, off_t skip, bool to_buffer);
 271
 272 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 273                            const void *buf, size_t buflen);
 274 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 275                          void *buf, size_t buflen);
 276
 277 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 278                             const void *buf, size_t buflen, off_t skip);
 279 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 280                           void *buf, size_t buflen, off_t skip);
 281 size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
 282                        size_t buflen, off_t skip);
 283
 284 /*
 285  * Maximum number of entries that will be allocated in one piece, if
 286  * a list larger than this is required then chaining will be utilized.
 287  */
 288 #define SG_MAX_SINGLE_ALLOC             (PAGE_SIZE / sizeof(struct scatterlist))
 289
 290 /*
 291  * The maximum number of SG segments that we will put inside a
 292  * scatterlist (unless chaining is used). Should ideally fit inside a
 293  * single page, to avoid a higher order allocation.  We could define this
 294  * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order.  The
 295  * minimum value is 32
 296  */
 297 #define SG_CHUNK_SIZE   128
 298
 299 /*
 300  * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
 301  * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
 302  */
 303 #ifdef CONFIG_ARCH_HAS_SG_CHAIN
 304 #define SG_MAX_SEGMENTS 2048
 305 #else
 306 #define SG_MAX_SEGMENTS SG_CHUNK_SIZE
 307 #endif
 308
 309 #ifdef CONFIG_SG_POOL
 310 void sg_free_table_chained(struct sg_table *table, bool first_chunk);
 311 int sg_alloc_table_chained(struct sg_table *table, int nents,
 312                            struct scatterlist *first_chunk);
 313 #endif
 314
 315 /*
 316  * sg page iterator
 317  *
 318  * Iterates over sg entries page-by-page.  On each successful iteration,
 319  * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
 320  * to get the current page and its dma address. @piter->sg will point to the
 321  * sg holding this page and @piter->sg_pgoffset to the page's page offset
 322  * within the sg. The iteration will stop either when a maximum number of sg
 323  * entries was reached or a terminating sg (sg_last(sg) == true) was reached.
 324  */
 325 struct sg_page_iter {
 326         struct scatterlist      *sg;            /* sg holding the page */
 327         unsigned int            sg_pgoffset;    /* page offset within the sg */
 328
 329         /* these are internal states, keep away */
 330         unsigned int            __nents;        /* remaining sg entries */
 331         int                     __pg_advance;   /* nr pages to advance at the
 332                                                  * next step */
 333 };
 334
 335 bool __sg_page_iter_next(struct sg_page_iter *piter);
 336 void __sg_page_iter_start(struct sg_page_iter *piter,
 337                           struct scatterlist *sglist, unsigned int nents,
 338                           unsigned long pgoffset);
 339 /**
 340  * sg_page_iter_page - get the current page held by the page iterator
 341  * @piter:      page iterator holding the page
 342  */
 343 static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
 344 {
 345         return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
 346 }
 347
 348 /**
 349  * sg_page_iter_dma_address - get the dma address of the current page held by
 350  * the page iterator.
 351  * @piter:      page iterator holding the page
 352  */
 353 static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter)
 354 {
 355         return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT);
 356 }
 357
 358 /**
 359  * for_each_sg_page - iterate over the pages of the given sg list
 360  * @sglist:     sglist to iterate over
 361  * @piter:      page iterator to hold current page, sg, sg_pgoffset
 362  * @nents:      maximum number of sg entries to iterate over
 363  * @pgoffset:   starting page offset
 364  */
 365 #define for_each_sg_page(sglist, piter, nents, pgoffset)                   \
 366         for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
 367              __sg_page_iter_next(piter);)
 368
 369 /*
 370  * Mapping sg iterator
 371  *
 372  * Iterates over sg entries mapping page-by-page.  On each successful
 373  * iteration, @miter->page points to the mapped page and
 374  * @miter->length bytes of data can be accessed at @miter->addr.  As
 375  * long as an interation is enclosed between start and stop, the user
 376  * is free to choose control structure and when to stop.
 377  *
 378  * @miter->consumed is set to @miter->length on each iteration.  It
 379  * can be adjusted if the user can't consume all the bytes in one go.
 380  * Also, a stopped iteration can be resumed by calling next on it.
 381  * This is useful when iteration needs to release all resources and
 382  * continue later (e.g. at the next interrupt).
 383  */
 384
 385 #define SG_MITER_ATOMIC         (1 << 0)         /* use kmap_atomic */
 386 #define SG_MITER_TO_SG          (1 << 1)        /* flush back to phys on unmap */
 387 #define SG_MITER_FROM_SG        (1 << 2)        /* nop */
 388
 389 struct sg_mapping_iter {
 390         /* the following three fields can be accessed directly */
 391         struct page             *page;          /* currently mapped page */
 392         void                    *addr;          /* pointer to the mapped area */
 393         size_t                  length;         /* length of the mapped area */
 394         size_t                  consumed;       /* number of consumed bytes */
 395         struct sg_page_iter     piter;          /* page iterator */
 396
 397         /* these are internal states, keep away */
 398         unsigned int            __offset;       /* offset within page */
 399         unsigned int            __remaining;    /* remaining bytes on page */
 400         unsigned int            __flags;
 401 };
 402
 403 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
 404                     unsigned int nents, unsigned int flags);
 405 bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
 406 bool sg_miter_next(struct sg_mapping_iter *miter);
 407 void sg_miter_stop(struct sg_mapping_iter *miter);
 408
 409 #endif /* _LINUX_SCATTERLIST_H */