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

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

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