xref: /linux/include/linux/scatterlist.h (revision 7296f230)
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