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 #ifdef CONFIG_NEED_SG_DMA_FLAGS
20 unsigned int dma_flags;
21 #endif
22 };
23
24 /*
25 * These macros should be used after a dma_map_sg call has been done
26 * to get bus addresses of each of the SG entries and their lengths.
27 * You should only work with the number of sg entries dma_map_sg
28 * returns, or alternatively stop on the first sg_dma_len(sg) which
29 * is 0.
30 */
31 #define sg_dma_address(sg) ((sg)->dma_address)
32
33 #ifdef CONFIG_NEED_SG_DMA_LENGTH
34 #define sg_dma_len(sg) ((sg)->dma_length)
35 #else
36 #define sg_dma_len(sg) ((sg)->length)
37 #endif
38
39 struct sg_table {
40 struct scatterlist *sgl; /* the list */
41 unsigned int nents; /* number of mapped entries */
42 unsigned int orig_nents; /* original size of list */
43 };
44
45 struct sg_append_table {
46 struct sg_table sgt; /* The scatter list table */
47 struct scatterlist *prv; /* last populated sge in the table */
48 unsigned int total_nents; /* Total entries in the table */
49 };
50
51 /*
52 * Notes on SG table design.
53 *
54 * We use the unsigned long page_link field in the scatterlist struct to place
55 * the page pointer AND encode information about the sg table as well. The two
56 * lower bits are reserved for this information.
57 *
58 * If bit 0 is set, then the page_link contains a pointer to the next sg
59 * table list. Otherwise the next entry is at sg + 1.
60 *
61 * If bit 1 is set, then this sg entry is the last element in a list.
62 *
63 * See sg_next().
64 *
65 */
66
67 #define SG_CHAIN 0x01UL
68 #define SG_END 0x02UL
69
70 /*
71 * We overload the LSB of the page pointer to indicate whether it's
72 * a valid sg entry, or whether it points to the start of a new scatterlist.
73 * Those low bits are there for everyone! (thanks mason :-)
74 */
75 #define SG_PAGE_LINK_MASK (SG_CHAIN | SG_END)
76
__sg_flags(struct scatterlist * sg)77 static inline unsigned int __sg_flags(struct scatterlist *sg)
78 {
79 return sg->page_link & SG_PAGE_LINK_MASK;
80 }
81
sg_chain_ptr(struct scatterlist * sg)82 static inline struct scatterlist *sg_chain_ptr(struct scatterlist *sg)
83 {
84 return (struct scatterlist *)(sg->page_link & ~SG_PAGE_LINK_MASK);
85 }
86
sg_is_chain(struct scatterlist * sg)87 static inline bool sg_is_chain(struct scatterlist *sg)
88 {
89 return __sg_flags(sg) & SG_CHAIN;
90 }
91
sg_is_last(struct scatterlist * sg)92 static inline bool sg_is_last(struct scatterlist *sg)
93 {
94 return __sg_flags(sg) & SG_END;
95 }
96
97 /**
98 * sg_assign_page - Assign a given page to an SG entry
99 * @sg: SG entry
100 * @page: The page
101 *
102 * Description:
103 * Assign page to sg entry. Also see sg_set_page(), the most commonly used
104 * variant.
105 *
106 **/
sg_assign_page(struct scatterlist * sg,struct page * page)107 static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
108 {
109 unsigned long page_link = sg->page_link & (SG_CHAIN | SG_END);
110
111 /*
112 * In order for the low bit stealing approach to work, pages
113 * must be aligned at a 32-bit boundary as a minimum.
114 */
115 BUG_ON((unsigned long)page & SG_PAGE_LINK_MASK);
116 #ifdef CONFIG_DEBUG_SG
117 BUG_ON(sg_is_chain(sg));
118 #endif
119 sg->page_link = page_link | (unsigned long) page;
120 }
121
122 /**
123 * sg_set_page - Set sg entry to point at given page
124 * @sg: SG entry
125 * @page: The page
126 * @len: Length of data
127 * @offset: Offset into page
128 *
129 * Description:
130 * Use this function to set an sg entry pointing at a page, never assign
131 * the page directly. We encode sg table information in the lower bits
132 * of the page pointer. See sg_page() for looking up the page belonging
133 * to an sg entry.
134 *
135 **/
sg_set_page(struct scatterlist * sg,struct page * page,unsigned int len,unsigned int offset)136 static inline void sg_set_page(struct scatterlist *sg, struct page *page,
137 unsigned int len, unsigned int offset)
138 {
139 sg_assign_page(sg, page);
140 sg->offset = offset;
141 sg->length = len;
142 }
143
144 /**
145 * sg_set_folio - Set sg entry to point at given folio
146 * @sg: SG entry
147 * @folio: The folio
148 * @len: Length of data
149 * @offset: Offset into folio
150 *
151 * Description:
152 * Use this function to set an sg entry pointing at a folio, never assign
153 * the folio directly. We encode sg table information in the lower bits
154 * of the folio pointer. See sg_page() for looking up the page belonging
155 * to an sg entry.
156 *
157 **/
sg_set_folio(struct scatterlist * sg,struct folio * folio,size_t len,size_t offset)158 static inline void sg_set_folio(struct scatterlist *sg, struct folio *folio,
159 size_t len, size_t offset)
160 {
161 WARN_ON_ONCE(len > UINT_MAX);
162 WARN_ON_ONCE(offset > UINT_MAX);
163 sg_assign_page(sg, &folio->page);
164 sg->offset = offset;
165 sg->length = len;
166 }
167
sg_page(struct scatterlist * sg)168 static inline struct page *sg_page(struct scatterlist *sg)
169 {
170 #ifdef CONFIG_DEBUG_SG
171 BUG_ON(sg_is_chain(sg));
172 #endif
173 return (struct page *)((sg)->page_link & ~SG_PAGE_LINK_MASK);
174 }
175
176 /**
177 * sg_set_buf - Set sg entry to point at given data
178 * @sg: SG entry
179 * @buf: Data
180 * @buflen: Data length
181 *
182 **/
sg_set_buf(struct scatterlist * sg,const void * buf,unsigned int buflen)183 static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
184 unsigned int buflen)
185 {
186 #ifdef CONFIG_DEBUG_SG
187 BUG_ON(!virt_addr_valid(buf));
188 #endif
189 sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
190 }
191
192 /*
193 * Loop over each sg element, following the pointer to a new list if necessary
194 */
195 #define for_each_sg(sglist, sg, nr, __i) \
196 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
197
198 /*
199 * Loop over each sg element in the given sg_table object.
200 */
201 #define for_each_sgtable_sg(sgt, sg, i) \
202 for_each_sg((sgt)->sgl, sg, (sgt)->orig_nents, i)
203
204 /*
205 * Loop over each sg element in the given *DMA mapped* sg_table object.
206 * Please use sg_dma_address(sg) and sg_dma_len(sg) to extract DMA addresses
207 * of the each element.
208 */
209 #define for_each_sgtable_dma_sg(sgt, sg, i) \
210 for_each_sg((sgt)->sgl, sg, (sgt)->nents, i)
211
__sg_chain(struct scatterlist * chain_sg,struct scatterlist * sgl)212 static inline void __sg_chain(struct scatterlist *chain_sg,
213 struct scatterlist *sgl)
214 {
215 /*
216 * offset and length are unused for chain entry. Clear them.
217 */
218 chain_sg->offset = 0;
219 chain_sg->length = 0;
220
221 /*
222 * Set lowest bit to indicate a link pointer, and make sure to clear
223 * the termination bit if it happens to be set.
224 */
225 chain_sg->page_link = ((unsigned long) sgl | SG_CHAIN) & ~SG_END;
226 }
227
228 /**
229 * sg_chain - Chain two sglists together
230 * @prv: First scatterlist
231 * @prv_nents: Number of entries in prv
232 * @sgl: Second scatterlist
233 *
234 * Description:
235 * Links @prv@ and @sgl@ together, to form a longer scatterlist.
236 *
237 **/
sg_chain(struct scatterlist * prv,unsigned int prv_nents,struct scatterlist * sgl)238 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
239 struct scatterlist *sgl)
240 {
241 __sg_chain(&prv[prv_nents - 1], sgl);
242 }
243
244 /**
245 * sg_mark_end - Mark the end of the scatterlist
246 * @sg: SG entryScatterlist
247 *
248 * Description:
249 * Marks the passed in sg entry as the termination point for the sg
250 * table. A call to sg_next() on this entry will return NULL.
251 *
252 **/
sg_mark_end(struct scatterlist * sg)253 static inline void sg_mark_end(struct scatterlist *sg)
254 {
255 /*
256 * Set termination bit, clear potential chain bit
257 */
258 sg->page_link |= SG_END;
259 sg->page_link &= ~SG_CHAIN;
260 }
261
262 /**
263 * sg_unmark_end - Undo setting the end of the scatterlist
264 * @sg: SG entryScatterlist
265 *
266 * Description:
267 * Removes the termination marker from the given entry of the scatterlist.
268 *
269 **/
sg_unmark_end(struct scatterlist * sg)270 static inline void sg_unmark_end(struct scatterlist *sg)
271 {
272 sg->page_link &= ~SG_END;
273 }
274
275 /*
276 * One 64-bit architectures there is a 4-byte padding in struct scatterlist
277 * (assuming also CONFIG_NEED_SG_DMA_LENGTH is set). Use this padding for DMA
278 * flags bits to indicate when a specific dma address is a bus address or the
279 * buffer may have been bounced via SWIOTLB.
280 */
281 #ifdef CONFIG_NEED_SG_DMA_FLAGS
282
283 #define SG_DMA_BUS_ADDRESS (1 << 0)
284 #define SG_DMA_SWIOTLB (1 << 1)
285
286 /**
287 * sg_dma_is_bus_address - Return whether a given segment was marked
288 * as a bus address
289 * @sg: SG entry
290 *
291 * Description:
292 * Returns true if sg_dma_mark_bus_address() has been called on
293 * this segment.
294 **/
sg_dma_is_bus_address(struct scatterlist * sg)295 static inline bool sg_dma_is_bus_address(struct scatterlist *sg)
296 {
297 return sg->dma_flags & SG_DMA_BUS_ADDRESS;
298 }
299
300 /**
301 * sg_dma_mark_bus_address - Mark the scatterlist entry as a bus address
302 * @sg: SG entry
303 *
304 * Description:
305 * Marks the passed in sg entry to indicate that the dma_address is
306 * a bus address and doesn't need to be unmapped. This should only be
307 * used by dma_map_sg() implementations to mark bus addresses
308 * so they can be properly cleaned up in dma_unmap_sg().
309 **/
sg_dma_mark_bus_address(struct scatterlist * sg)310 static inline void sg_dma_mark_bus_address(struct scatterlist *sg)
311 {
312 sg->dma_flags |= SG_DMA_BUS_ADDRESS;
313 }
314
315 /**
316 * sg_unmark_bus_address - Unmark the scatterlist entry as a bus address
317 * @sg: SG entry
318 *
319 * Description:
320 * Clears the bus address mark.
321 **/
sg_dma_unmark_bus_address(struct scatterlist * sg)322 static inline void sg_dma_unmark_bus_address(struct scatterlist *sg)
323 {
324 sg->dma_flags &= ~SG_DMA_BUS_ADDRESS;
325 }
326
327 /**
328 * sg_dma_is_swiotlb - Return whether the scatterlist was marked for SWIOTLB
329 * bouncing
330 * @sg: SG entry
331 *
332 * Description:
333 * Returns true if the scatterlist was marked for SWIOTLB bouncing. Not all
334 * elements may have been bounced, so the caller would have to check
335 * individual SG entries with swiotlb_find_pool().
336 */
sg_dma_is_swiotlb(struct scatterlist * sg)337 static inline bool sg_dma_is_swiotlb(struct scatterlist *sg)
338 {
339 return sg->dma_flags & SG_DMA_SWIOTLB;
340 }
341
342 /**
343 * sg_dma_mark_swiotlb - Mark the scatterlist for SWIOTLB bouncing
344 * @sg: SG entry
345 *
346 * Description:
347 * Marks a a scatterlist for SWIOTLB bounce. Not all SG entries may be
348 * bounced.
349 */
sg_dma_mark_swiotlb(struct scatterlist * sg)350 static inline void sg_dma_mark_swiotlb(struct scatterlist *sg)
351 {
352 sg->dma_flags |= SG_DMA_SWIOTLB;
353 }
354
355 #else
356
sg_dma_is_bus_address(struct scatterlist * sg)357 static inline bool sg_dma_is_bus_address(struct scatterlist *sg)
358 {
359 return false;
360 }
sg_dma_mark_bus_address(struct scatterlist * sg)361 static inline void sg_dma_mark_bus_address(struct scatterlist *sg)
362 {
363 }
sg_dma_unmark_bus_address(struct scatterlist * sg)364 static inline void sg_dma_unmark_bus_address(struct scatterlist *sg)
365 {
366 }
sg_dma_is_swiotlb(struct scatterlist * sg)367 static inline bool sg_dma_is_swiotlb(struct scatterlist *sg)
368 {
369 return false;
370 }
sg_dma_mark_swiotlb(struct scatterlist * sg)371 static inline void sg_dma_mark_swiotlb(struct scatterlist *sg)
372 {
373 }
374
375 #endif /* CONFIG_NEED_SG_DMA_FLAGS */
376
377 /**
378 * sg_phys - Return physical address of an sg entry
379 * @sg: SG entry
380 *
381 * Description:
382 * This calls page_to_phys() on the page in this sg entry, and adds the
383 * sg offset. The caller must know that it is legal to call page_to_phys()
384 * on the sg page.
385 *
386 **/
sg_phys(struct scatterlist * sg)387 static inline dma_addr_t sg_phys(struct scatterlist *sg)
388 {
389 return page_to_phys(sg_page(sg)) + sg->offset;
390 }
391
392 /**
393 * sg_virt - Return virtual address of an sg entry
394 * @sg: SG entry
395 *
396 * Description:
397 * This calls page_address() on the page in this sg entry, and adds the
398 * sg offset. The caller must know that the sg page has a valid virtual
399 * mapping.
400 *
401 **/
sg_virt(struct scatterlist * sg)402 static inline void *sg_virt(struct scatterlist *sg)
403 {
404 return page_address(sg_page(sg)) + sg->offset;
405 }
406
407 /**
408 * sg_init_marker - Initialize markers in sg table
409 * @sgl: The SG table
410 * @nents: Number of entries in table
411 *
412 **/
sg_init_marker(struct scatterlist * sgl,unsigned int nents)413 static inline void sg_init_marker(struct scatterlist *sgl,
414 unsigned int nents)
415 {
416 sg_mark_end(&sgl[nents - 1]);
417 }
418
419 int sg_nents(struct scatterlist *sg);
420 int sg_nents_for_len(struct scatterlist *sg, u64 len);
421 struct scatterlist *sg_next(struct scatterlist *);
422 struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
423 void sg_init_table(struct scatterlist *, unsigned int);
424 void sg_init_one(struct scatterlist *, const void *, unsigned int);
425 int sg_split(struct scatterlist *in, const int in_mapped_nents,
426 const off_t skip, const int nb_splits,
427 const size_t *split_sizes,
428 struct scatterlist **out, int *out_mapped_nents,
429 gfp_t gfp_mask);
430
431 typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
432 typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
433
434 void __sg_free_table(struct sg_table *, unsigned int, unsigned int,
435 sg_free_fn *, unsigned int);
436 void sg_free_table(struct sg_table *);
437 void sg_free_append_table(struct sg_append_table *sgt);
438 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
439 struct scatterlist *, unsigned int, gfp_t, sg_alloc_fn *);
440 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
441 int sg_alloc_append_table_from_pages(struct sg_append_table *sgt,
442 struct page **pages, unsigned int n_pages,
443 unsigned int offset, unsigned long size,
444 unsigned int max_segment,
445 unsigned int left_pages, gfp_t gfp_mask);
446 int sg_alloc_table_from_pages_segment(struct sg_table *sgt, struct page **pages,
447 unsigned int n_pages, unsigned int offset,
448 unsigned long size,
449 unsigned int max_segment, gfp_t gfp_mask);
450
451 /**
452 * sg_alloc_table_from_pages - Allocate and initialize an sg table from
453 * an array of pages
454 * @sgt: The sg table header to use
455 * @pages: Pointer to an array of page pointers
456 * @n_pages: Number of pages in the pages array
457 * @offset: Offset from start of the first page to the start of a buffer
458 * @size: Number of valid bytes in the buffer (after offset)
459 * @gfp_mask: GFP allocation mask
460 *
461 * Description:
462 * Allocate and initialize an sg table from a list of pages. Contiguous
463 * ranges of the pages are squashed into a single scatterlist node. A user
464 * may provide an offset at a start and a size of valid data in a buffer
465 * specified by the page array. The returned sg table is released by
466 * sg_free_table.
467 *
468 * Returns:
469 * 0 on success, negative error on failure
470 */
sg_alloc_table_from_pages(struct sg_table * sgt,struct page ** pages,unsigned int n_pages,unsigned int offset,unsigned long size,gfp_t gfp_mask)471 static inline int sg_alloc_table_from_pages(struct sg_table *sgt,
472 struct page **pages,
473 unsigned int n_pages,
474 unsigned int offset,
475 unsigned long size, gfp_t gfp_mask)
476 {
477 return sg_alloc_table_from_pages_segment(sgt, pages, n_pages, offset,
478 size, UINT_MAX, gfp_mask);
479 }
480
481 #ifdef CONFIG_SGL_ALLOC
482 struct scatterlist *sgl_alloc_order(unsigned long long length,
483 unsigned int order, bool chainable,
484 gfp_t gfp, unsigned int *nent_p);
485 struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
486 unsigned int *nent_p);
487 void sgl_free_n_order(struct scatterlist *sgl, int nents, int order);
488 void sgl_free_order(struct scatterlist *sgl, int order);
489 void sgl_free(struct scatterlist *sgl);
490 #endif /* CONFIG_SGL_ALLOC */
491
492 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
493 size_t buflen, off_t skip, bool to_buffer);
494
495 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
496 const void *buf, size_t buflen);
497 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
498 void *buf, size_t buflen);
499
500 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
501 const void *buf, size_t buflen, off_t skip);
502 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
503 void *buf, size_t buflen, off_t skip);
504 size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
505 size_t buflen, off_t skip);
506
507 /*
508 * Maximum number of entries that will be allocated in one piece, if
509 * a list larger than this is required then chaining will be utilized.
510 */
511 #define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
512
513 /*
514 * The maximum number of SG segments that we will put inside a
515 * scatterlist (unless chaining is used). Should ideally fit inside a
516 * single page, to avoid a higher order allocation. We could define this
517 * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order. The
518 * minimum value is 32
519 */
520 #define SG_CHUNK_SIZE 128
521
522 /*
523 * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
524 * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
525 */
526 #ifdef CONFIG_ARCH_NO_SG_CHAIN
527 #define SG_MAX_SEGMENTS SG_CHUNK_SIZE
528 #else
529 #define SG_MAX_SEGMENTS 2048
530 #endif
531
532 #ifdef CONFIG_SG_POOL
533 void sg_free_table_chained(struct sg_table *table,
534 unsigned nents_first_chunk);
535 int sg_alloc_table_chained(struct sg_table *table, int nents,
536 struct scatterlist *first_chunk,
537 unsigned nents_first_chunk);
538 #endif
539
540 /*
541 * sg page iterator
542 *
543 * Iterates over sg entries page-by-page. On each successful iteration, you
544 * can call sg_page_iter_page(@piter) to get the current page.
545 * @piter->sg will point to the sg holding this page and @piter->sg_pgoffset to
546 * the page's page offset within the sg. The iteration will stop either when a
547 * maximum number of sg entries was reached or a terminating sg
548 * (sg_last(sg) == true) was reached.
549 */
550 struct sg_page_iter {
551 struct scatterlist *sg; /* sg holding the page */
552 unsigned int sg_pgoffset; /* page offset within the sg */
553
554 /* these are internal states, keep away */
555 unsigned int __nents; /* remaining sg entries */
556 int __pg_advance; /* nr pages to advance at the
557 * next step */
558 };
559
560 /*
561 * sg page iterator for DMA addresses
562 *
563 * This is the same as sg_page_iter however you can call
564 * sg_page_iter_dma_address(@dma_iter) to get the page's DMA
565 * address. sg_page_iter_page() cannot be called on this iterator.
566 */
567 struct sg_dma_page_iter {
568 struct sg_page_iter base;
569 };
570
571 bool __sg_page_iter_next(struct sg_page_iter *piter);
572 bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter);
573 void __sg_page_iter_start(struct sg_page_iter *piter,
574 struct scatterlist *sglist, unsigned int nents,
575 unsigned long pgoffset);
576 /**
577 * sg_page_iter_page - get the current page held by the page iterator
578 * @piter: page iterator holding the page
579 */
sg_page_iter_page(struct sg_page_iter * piter)580 static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
581 {
582 return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
583 }
584
585 /**
586 * sg_page_iter_dma_address - get the dma address of the current page held by
587 * the page iterator.
588 * @dma_iter: page iterator holding the page
589 */
590 static inline dma_addr_t
sg_page_iter_dma_address(struct sg_dma_page_iter * dma_iter)591 sg_page_iter_dma_address(struct sg_dma_page_iter *dma_iter)
592 {
593 return sg_dma_address(dma_iter->base.sg) +
594 (dma_iter->base.sg_pgoffset << PAGE_SHIFT);
595 }
596
597 /**
598 * for_each_sg_page - iterate over the pages of the given sg list
599 * @sglist: sglist to iterate over
600 * @piter: page iterator to hold current page, sg, sg_pgoffset
601 * @nents: maximum number of sg entries to iterate over
602 * @pgoffset: starting page offset (in pages)
603 *
604 * Callers may use sg_page_iter_page() to get each page pointer.
605 * In each loop it operates on PAGE_SIZE unit.
606 */
607 #define for_each_sg_page(sglist, piter, nents, pgoffset) \
608 for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
609 __sg_page_iter_next(piter);)
610
611 /**
612 * for_each_sg_dma_page - iterate over the pages of the given sg list
613 * @sglist: sglist to iterate over
614 * @dma_iter: DMA page iterator to hold current page
615 * @dma_nents: maximum number of sg entries to iterate over, this is the value
616 * returned from dma_map_sg
617 * @pgoffset: starting page offset (in pages)
618 *
619 * Callers may use sg_page_iter_dma_address() to get each page's DMA address.
620 * In each loop it operates on PAGE_SIZE unit.
621 */
622 #define for_each_sg_dma_page(sglist, dma_iter, dma_nents, pgoffset) \
623 for (__sg_page_iter_start(&(dma_iter)->base, sglist, dma_nents, \
624 pgoffset); \
625 __sg_page_iter_dma_next(dma_iter);)
626
627 /**
628 * for_each_sgtable_page - iterate over all pages in the sg_table object
629 * @sgt: sg_table object to iterate over
630 * @piter: page iterator to hold current page
631 * @pgoffset: starting page offset (in pages)
632 *
633 * Iterates over the all memory pages in the buffer described by
634 * a scatterlist stored in the given sg_table object.
635 * See also for_each_sg_page(). In each loop it operates on PAGE_SIZE unit.
636 */
637 #define for_each_sgtable_page(sgt, piter, pgoffset) \
638 for_each_sg_page((sgt)->sgl, piter, (sgt)->orig_nents, pgoffset)
639
640 /**
641 * for_each_sgtable_dma_page - iterate over the DMA mapped sg_table object
642 * @sgt: sg_table object to iterate over
643 * @dma_iter: DMA page iterator to hold current page
644 * @pgoffset: starting page offset (in pages)
645 *
646 * Iterates over the all DMA mapped pages in the buffer described by
647 * a scatterlist stored in the given sg_table object.
648 * See also for_each_sg_dma_page(). In each loop it operates on PAGE_SIZE
649 * unit.
650 */
651 #define for_each_sgtable_dma_page(sgt, dma_iter, pgoffset) \
652 for_each_sg_dma_page((sgt)->sgl, dma_iter, (sgt)->nents, pgoffset)
653
654
655 /*
656 * Mapping sg iterator
657 *
658 * Iterates over sg entries mapping page-by-page. On each successful
659 * iteration, @miter->page points to the mapped page and
660 * @miter->length bytes of data can be accessed at @miter->addr. As
661 * long as an iteration is enclosed between start and stop, the user
662 * is free to choose control structure and when to stop.
663 *
664 * @miter->consumed is set to @miter->length on each iteration. It
665 * can be adjusted if the user can't consume all the bytes in one go.
666 * Also, a stopped iteration can be resumed by calling next on it.
667 * This is useful when iteration needs to release all resources and
668 * continue later (e.g. at the next interrupt).
669 */
670
671 #define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */
672 #define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */
673 #define SG_MITER_FROM_SG (1 << 2) /* nop */
674
675 struct sg_mapping_iter {
676 /* the following three fields can be accessed directly */
677 struct page *page; /* currently mapped page */
678 void *addr; /* pointer to the mapped area */
679 size_t length; /* length of the mapped area */
680 size_t consumed; /* number of consumed bytes */
681 struct sg_page_iter piter; /* page iterator */
682
683 /* these are internal states, keep away */
684 unsigned int __offset; /* offset within page */
685 unsigned int __remaining; /* remaining bytes on page */
686 unsigned int __flags;
687 };
688
689 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
690 unsigned int nents, unsigned int flags);
691 bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
692 bool sg_miter_next(struct sg_mapping_iter *miter);
693 void sg_miter_stop(struct sg_mapping_iter *miter);
694
695 #endif /* _LINUX_SCATTERLIST_H */
696