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TOMOYO Linux Cross Reference
Linux/include/linux/scatterlist.h

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  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 */
410 

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