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 #ifndef CONFIG_ARCH_HAS_SG_CHAIN
 165         BUG();
 166 #endif
 167
 168         /*
 169          * offset and length are unused for chain entry.  Clear them.
 170          */
 171         prv[prv_nents - 1].offset = 0;
 172         prv[prv_nents - 1].length = 0;
 173
 174         /*
 175          * Set lowest bit to indicate a link pointer, and make sure to clear
 176          * the termination bit if it happens to be set.
 177          */
 178         prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
 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 #ifdef CONFIG_DEBUG_SG
 193         BUG_ON(sg->sg_magic != SG_MAGIC);
 194 #endif
 195         /*
 196          * Set termination bit, clear potential chain bit
 197          */
 198         sg->page_link |= 0x02;
 199         sg->page_link &= ~0x01;
 200 }
 201
 202 /**
 203  * sg_unmark_end - Undo setting the end of the scatterlist
 204  * @sg:          SG entryScatterlist
 205  *
 206  * Description:
 207  *   Removes the termination marker from the given entry of the scatterlist.
 208  *
 209  **/
 210 static inline void sg_unmark_end(struct scatterlist *sg)
 211 {
 212 #ifdef CONFIG_DEBUG_SG
 213         BUG_ON(sg->sg_magic != SG_MAGIC);
 214 #endif
 215         sg->page_link &= ~0x02;
 216 }
 217
 218 /**
 219  * sg_phys - Return physical address of an sg entry
 220  * @sg:      SG entry
 221  *
 222  * Description:
 223  *   This calls page_to_phys() on the page in this sg entry, and adds the
 224  *   sg offset. The caller must know that it is legal to call page_to_phys()
 225  *   on the sg page.
 226  *
 227  **/
 228 static inline dma_addr_t sg_phys(struct scatterlist *sg)
 229 {
 230         return page_to_phys(sg_page(sg)) + sg->offset;
 231 }
 232
 233 /**
 234  * sg_virt - Return virtual address of an sg entry
 235  * @sg:      SG entry
 236  *
 237  * Description:
 238  *   This calls page_address() on the page in this sg entry, and adds the
 239  *   sg offset. The caller must know that the sg page has a valid virtual
 240  *   mapping.
 241  *
 242  **/
 243 static inline void *sg_virt(struct scatterlist *sg)
 244 {
 245         return page_address(sg_page(sg)) + sg->offset;
 246 }
 247
 248 int sg_nents(struct scatterlist *sg);
 249 int sg_nents_for_len(struct scatterlist *sg, u64 len);
 250 struct scatterlist *sg_next(struct scatterlist *);
 251 struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
 252 void sg_init_table(struct scatterlist *, unsigned int);
 253 void sg_init_one(struct scatterlist *, const void *, unsigned int);
 254
 255 typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
 256 typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
 257
 258 void __sg_free_table(struct sg_table *, unsigned int, bool, sg_free_fn *);
 259 void sg_free_table(struct sg_table *);
 260 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
 261                      struct scatterlist *, gfp_t, sg_alloc_fn *);
 262 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
 263 int sg_alloc_table_from_pages(struct sg_table *sgt,
 264         struct page **pages, unsigned int n_pages,
 265         unsigned long offset, unsigned long size,
 266         gfp_t gfp_mask);
 267
 268 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
 269                       size_t buflen, off_t skip, bool to_buffer);
 270
 271 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 272                            const void *buf, size_t buflen);
 273 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 274                          void *buf, size_t buflen);
 275
 276 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 277                             const void *buf, size_t buflen, off_t skip);
 278 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 279                           void *buf, size_t buflen, off_t skip);
 280
 281 /*
 282  * Maximum number of entries that will be allocated in one piece, if
 283  * a list larger than this is required then chaining will be utilized.
 284  */
 285 #define SG_MAX_SINGLE_ALLOC             (PAGE_SIZE / sizeof(struct scatterlist))
 286
 287 /*
 288  * sg page iterator
 289  *
 290  * Iterates over sg entries page-by-page.  On each successful iteration,
 291  * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
 292  * to get the current page and its dma address. @piter->sg will point to the
 293  * sg holding this page and @piter->sg_pgoffset to the page's page offset
 294  * within the sg. The iteration will stop either when a maximum number of sg
 295  * entries was reached or a terminating sg (sg_last(sg) == true) was reached.
 296  */
 297 struct sg_page_iter {
 298         struct scatterlist      *sg;            /* sg holding the page */
 299         unsigned int            sg_pgoffset;    /* page offset within the sg */
 300
 301         /* these are internal states, keep away */
 302         unsigned int            __nents;        /* remaining sg entries */
 303         int                     __pg_advance;   /* nr pages to advance at the
 304                                                  * next step */
 305 };
 306
 307 bool __sg_page_iter_next(struct sg_page_iter *piter);
 308 void __sg_page_iter_start(struct sg_page_iter *piter,
 309                           struct scatterlist *sglist, unsigned int nents,
 310                           unsigned long pgoffset);
 311 /**
 312  * sg_page_iter_page - get the current page held by the page iterator
 313  * @piter:      page iterator holding the page
 314  */
 315 static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
 316 {
 317         return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
 318 }
 319
 320 /**
 321  * sg_page_iter_dma_address - get the dma address of the current page held by
 322  * the page iterator.
 323  * @piter:      page iterator holding the page
 324  */
 325 static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter)
 326 {
 327         return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT);
 328 }
 329
 330 /**
 331  * for_each_sg_page - iterate over the pages of the given sg list
 332  * @sglist:     sglist to iterate over
 333  * @piter:      page iterator to hold current page, sg, sg_pgoffset
 334  * @nents:      maximum number of sg entries to iterate over
 335  * @pgoffset:   starting page offset
 336  */
 337 #define for_each_sg_page(sglist, piter, nents, pgoffset)                   \
 338         for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
 339              __sg_page_iter_next(piter);)
 340
 341 /*
 342  * Mapping sg iterator
 343  *
 344  * Iterates over sg entries mapping page-by-page.  On each successful
 345  * iteration, @miter->page points to the mapped page and
 346  * @miter->length bytes of data can be accessed at @miter->addr.  As
 347  * long as an interation is enclosed between start and stop, the user
 348  * is free to choose control structure and when to stop.
 349  *
 350  * @miter->consumed is set to @miter->length on each iteration.  It
 351  * can be adjusted if the user can't consume all the bytes in one go.
 352  * Also, a stopped iteration can be resumed by calling next on it.
 353  * This is useful when iteration needs to release all resources and
 354  * continue later (e.g. at the next interrupt).
 355  */
 356
 357 #define SG_MITER_ATOMIC         (1 << 0)         /* use kmap_atomic */
 358 #define SG_MITER_TO_SG          (1 << 1)        /* flush back to phys on unmap */
 359 #define SG_MITER_FROM_SG        (1 << 2)        /* nop */
 360
 361 struct sg_mapping_iter {
 362         /* the following three fields can be accessed directly */
 363         struct page             *page;          /* currently mapped page */
 364         void                    *addr;          /* pointer to the mapped area */
 365         size_t                  length;         /* length of the mapped area */
 366         size_t                  consumed;       /* number of consumed bytes */
 367         struct sg_page_iter     piter;          /* page iterator */
 368
 369         /* these are internal states, keep away */
 370         unsigned int            __offset;       /* offset within page */
 371         unsigned int            __remaining;    /* remaining bytes on page */
 372         unsigned int            __flags;
 373 };
 374
 375 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
 376                     unsigned int nents, unsigned int flags);
 377 bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
 378 bool sg_miter_next(struct sg_mapping_iter *miter);
 379 void sg_miter_stop(struct sg_mapping_iter *miter);
 380
 381 #endif /* _LINUX_SCATTERLIST_H */