LCOV - code coverage report
Current view: top level - include/linux - scatterlist.h (source / functions) Hit Total Coverage
Test: combined.info Lines: 30 34 88.2 %
Date: 2022-03-28 16:04:14 Functions: 1 2 50.0 %
Branches: 7 32 21.9 %

           Branch data     Line data    Source code
       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                 :      50578 : static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
      88                 :            : {
      89                 :      50578 :         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         [ #  # ]:          0 :         BUG_ON((unsigned long) page & (SG_CHAIN | SG_END));
      96                 :            : #ifdef CONFIG_DEBUG_SG
      97                 :            :         BUG_ON(sg_is_chain(sg));
      98                 :            : #endif
      99                 :      50578 :         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                 :      50578 : static inline void sg_set_page(struct scatterlist *sg, struct page *page,
     117                 :            :                                unsigned int len, unsigned int offset)
     118                 :            : {
     119   [ -  +  -  +  :      50344 :         sg_assign_page(sg, page);
                   -  + ]
     120                 :      50578 :         sg->offset = offset;
     121   [ #  #  #  # ]:      14509 :         sg->length = len;
     122                 :          0 : }
     123                 :            : 
     124                 :     196481 : 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   [ -  -  -  -  :     146436 :         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                 :        273 : 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   [ +  -  -  + ]:        546 :         sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
     146                 :        273 : }
     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                 :       3917 : 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                 :       3917 :         prv[prv_nents - 1].offset = 0;
     171                 :       3917 :         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                 :       3917 :         prv[prv_nents - 1].page_link = ((unsigned long) sgl | SG_CHAIN)
     178                 :       3917 :                                         & ~SG_END;
     179                 :       3917 : }
     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                 :      36873 : static inline void sg_mark_end(struct scatterlist *sg)
     191                 :            : {
     192                 :            :         /*
     193                 :            :          * Set termination bit, clear potential chain bit
     194                 :            :          */
     195                 :      36873 :         sg->page_link |= SG_END;
     196                 :      36873 :         sg->page_link &= ~SG_CHAIN;
     197                 :      18261 : }
     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                 :      35961 : static inline void sg_unmark_end(struct scatterlist *sg)
     208                 :            : {
     209   [ #  #  #  # ]:      35961 :         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                 :          0 : static inline dma_addr_t sg_phys(struct scatterlist *sg)
     223                 :            : {
     224         [ #  # ]:          0 :         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                 :      48667 : static inline void *sg_virt(struct scatterlist *sg)
     238                 :            : {
     239         [ #  # ]:      48667 :         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                 :      18612 : static inline void sg_init_marker(struct scatterlist *sgl,
     249                 :            :                                   unsigned int nents)
     250                 :            : {
     251                 :        234 :         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, unsigned int,
     270                 :            :                      sg_free_fn *);
     271                 :            : void sg_free_table(struct sg_table *);
     272                 :            : int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
     273                 :            :                      struct scatterlist *, unsigned int, gfp_t, sg_alloc_fn *);
     274                 :            : int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
     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, unsigned int max_segment,
     278                 :            :                                 gfp_t gfp_mask);
     279                 :            : int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
     280                 :            :                               unsigned int n_pages, unsigned int offset,
     281                 :            :                               unsigned long size, gfp_t gfp_mask);
     282                 :            : 
     283                 :            : #ifdef CONFIG_SGL_ALLOC
     284                 :            : struct scatterlist *sgl_alloc_order(unsigned long long length,
     285                 :            :                                     unsigned int order, bool chainable,
     286                 :            :                                     gfp_t gfp, unsigned int *nent_p);
     287                 :            : struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
     288                 :            :                               unsigned int *nent_p);
     289                 :            : void sgl_free_n_order(struct scatterlist *sgl, int nents, int order);
     290                 :            : void sgl_free_order(struct scatterlist *sgl, int order);
     291                 :            : void sgl_free(struct scatterlist *sgl);
     292                 :            : #endif /* CONFIG_SGL_ALLOC */
     293                 :            : 
     294                 :            : size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
     295                 :            :                       size_t buflen, off_t skip, bool to_buffer);
     296                 :            : 
     297                 :            : size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
     298                 :            :                            const void *buf, size_t buflen);
     299                 :            : size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
     300                 :            :                          void *buf, size_t buflen);
     301                 :            : 
     302                 :            : size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
     303                 :            :                             const void *buf, size_t buflen, off_t skip);
     304                 :            : size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
     305                 :            :                           void *buf, size_t buflen, off_t skip);
     306                 :            : size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
     307                 :            :                        size_t buflen, off_t skip);
     308                 :            : 
     309                 :            : /*
     310                 :            :  * Maximum number of entries that will be allocated in one piece, if
     311                 :            :  * a list larger than this is required then chaining will be utilized.
     312                 :            :  */
     313                 :            : #define SG_MAX_SINGLE_ALLOC             (PAGE_SIZE / sizeof(struct scatterlist))
     314                 :            : 
     315                 :            : /*
     316                 :            :  * The maximum number of SG segments that we will put inside a
     317                 :            :  * scatterlist (unless chaining is used). Should ideally fit inside a
     318                 :            :  * single page, to avoid a higher order allocation.  We could define this
     319                 :            :  * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order.  The
     320                 :            :  * minimum value is 32
     321                 :            :  */
     322                 :            : #define SG_CHUNK_SIZE   128
     323                 :            : 
     324                 :            : /*
     325                 :            :  * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
     326                 :            :  * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
     327                 :            :  */
     328                 :            : #ifdef CONFIG_ARCH_NO_SG_CHAIN
     329                 :            : #define SG_MAX_SEGMENTS SG_CHUNK_SIZE
     330                 :            : #else
     331                 :            : #define SG_MAX_SEGMENTS 2048
     332                 :            : #endif
     333                 :            : 
     334                 :            : #ifdef CONFIG_SG_POOL
     335                 :            : void sg_free_table_chained(struct sg_table *table,
     336                 :            :                            unsigned nents_first_chunk);
     337                 :            : int sg_alloc_table_chained(struct sg_table *table, int nents,
     338                 :            :                            struct scatterlist *first_chunk,
     339                 :            :                            unsigned nents_first_chunk);
     340                 :            : #endif
     341                 :            : 
     342                 :            : /*
     343                 :            :  * sg page iterator
     344                 :            :  *
     345                 :            :  * Iterates over sg entries page-by-page.  On each successful iteration, you
     346                 :            :  * can call sg_page_iter_page(@piter) to get the current page.
     347                 :            :  * @piter->sg will point to the sg holding this page and @piter->sg_pgoffset to
     348                 :            :  * the page's page offset within the sg. The iteration will stop either when a
     349                 :            :  * maximum number of sg entries was reached or a terminating sg
     350                 :            :  * (sg_last(sg) == true) was reached.
     351                 :            :  */
     352                 :            : struct sg_page_iter {
     353                 :            :         struct scatterlist      *sg;            /* sg holding the page */
     354                 :            :         unsigned int            sg_pgoffset;    /* page offset within the sg */
     355                 :            : 
     356                 :            :         /* these are internal states, keep away */
     357                 :            :         unsigned int            __nents;        /* remaining sg entries */
     358                 :            :         int                     __pg_advance;   /* nr pages to advance at the
     359                 :            :                                                  * next step */
     360                 :            : };
     361                 :            : 
     362                 :            : /*
     363                 :            :  * sg page iterator for DMA addresses
     364                 :            :  *
     365                 :            :  * This is the same as sg_page_iter however you can call
     366                 :            :  * sg_page_iter_dma_address(@dma_iter) to get the page's DMA
     367                 :            :  * address. sg_page_iter_page() cannot be called on this iterator.
     368                 :            :  */
     369                 :            : struct sg_dma_page_iter {
     370                 :            :         struct sg_page_iter base;
     371                 :            : };
     372                 :            : 
     373                 :            : bool __sg_page_iter_next(struct sg_page_iter *piter);
     374                 :            : bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter);
     375                 :            : void __sg_page_iter_start(struct sg_page_iter *piter,
     376                 :            :                           struct scatterlist *sglist, unsigned int nents,
     377                 :            :                           unsigned long pgoffset);
     378                 :            : /**
     379                 :            :  * sg_page_iter_page - get the current page held by the page iterator
     380                 :            :  * @piter:      page iterator holding the page
     381                 :            :  */
     382                 :       1378 : static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
     383                 :            : {
     384         [ +  - ]:       1378 :         return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
     385                 :            : }
     386                 :            : 
     387                 :            : /**
     388                 :            :  * sg_page_iter_dma_address - get the dma address of the current page held by
     389                 :            :  * the page iterator.
     390                 :            :  * @dma_iter:   page iterator holding the page
     391                 :            :  */
     392                 :            : static inline dma_addr_t
     393                 :            : sg_page_iter_dma_address(struct sg_dma_page_iter *dma_iter)
     394                 :            : {
     395                 :            :         return sg_dma_address(dma_iter->base.sg) +
     396                 :            :                (dma_iter->base.sg_pgoffset << PAGE_SHIFT);
     397                 :            : }
     398                 :            : 
     399                 :            : /**
     400                 :            :  * for_each_sg_page - iterate over the pages of the given sg list
     401                 :            :  * @sglist:     sglist to iterate over
     402                 :            :  * @piter:      page iterator to hold current page, sg, sg_pgoffset
     403                 :            :  * @nents:      maximum number of sg entries to iterate over
     404                 :            :  * @pgoffset:   starting page offset
     405                 :            :  *
     406                 :            :  * Callers may use sg_page_iter_page() to get each page pointer.
     407                 :            :  */
     408                 :            : #define for_each_sg_page(sglist, piter, nents, pgoffset)                   \
     409                 :            :         for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
     410                 :            :              __sg_page_iter_next(piter);)
     411                 :            : 
     412                 :            : /**
     413                 :            :  * for_each_sg_dma_page - iterate over the pages of the given sg list
     414                 :            :  * @sglist:     sglist to iterate over
     415                 :            :  * @dma_iter:   page iterator to hold current page
     416                 :            :  * @dma_nents:  maximum number of sg entries to iterate over, this is the value
     417                 :            :  *              returned from dma_map_sg
     418                 :            :  * @pgoffset:   starting page offset
     419                 :            :  *
     420                 :            :  * Callers may use sg_page_iter_dma_address() to get each page's DMA address.
     421                 :            :  */
     422                 :            : #define for_each_sg_dma_page(sglist, dma_iter, dma_nents, pgoffset)            \
     423                 :            :         for (__sg_page_iter_start(&(dma_iter)->base, sglist, dma_nents,        \
     424                 :            :                                   pgoffset);                                   \
     425                 :            :              __sg_page_iter_dma_next(dma_iter);)
     426                 :            : 
     427                 :            : /*
     428                 :            :  * Mapping sg iterator
     429                 :            :  *
     430                 :            :  * Iterates over sg entries mapping page-by-page.  On each successful
     431                 :            :  * iteration, @miter->page points to the mapped page and
     432                 :            :  * @miter->length bytes of data can be accessed at @miter->addr.  As
     433                 :            :  * long as an interation is enclosed between start and stop, the user
     434                 :            :  * is free to choose control structure and when to stop.
     435                 :            :  *
     436                 :            :  * @miter->consumed is set to @miter->length on each iteration.  It
     437                 :            :  * can be adjusted if the user can't consume all the bytes in one go.
     438                 :            :  * Also, a stopped iteration can be resumed by calling next on it.
     439                 :            :  * This is useful when iteration needs to release all resources and
     440                 :            :  * continue later (e.g. at the next interrupt).
     441                 :            :  */
     442                 :            : 
     443                 :            : #define SG_MITER_ATOMIC         (1 << 0)   /* use kmap_atomic */
     444                 :            : #define SG_MITER_TO_SG          (1 << 1)  /* flush back to phys on unmap */
     445                 :            : #define SG_MITER_FROM_SG        (1 << 2)  /* nop */
     446                 :            : 
     447                 :            : struct sg_mapping_iter {
     448                 :            :         /* the following three fields can be accessed directly */
     449                 :            :         struct page             *page;          /* currently mapped page */
     450                 :            :         void                    *addr;          /* pointer to the mapped area */
     451                 :            :         size_t                  length;         /* length of the mapped area */
     452                 :            :         size_t                  consumed;       /* number of consumed bytes */
     453                 :            :         struct sg_page_iter     piter;          /* page iterator */
     454                 :            : 
     455                 :            :         /* these are internal states, keep away */
     456                 :            :         unsigned int            __offset;       /* offset within page */
     457                 :            :         unsigned int            __remaining;    /* remaining bytes on page */
     458                 :            :         unsigned int            __flags;
     459                 :            : };
     460                 :            : 
     461                 :            : void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
     462                 :            :                     unsigned int nents, unsigned int flags);
     463                 :            : bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
     464                 :            : bool sg_miter_next(struct sg_mapping_iter *miter);
     465                 :            : void sg_miter_stop(struct sg_mapping_iter *miter);
     466                 :            : 
     467                 :            : #endif /* _LINUX_SCATTERLIST_H */

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