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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
11struct 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
42struct 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 **/
87static 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 **/
116static 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
124static 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 **/
139static 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 * Loop over each sg element in the given sg_table object.
156 */
157#define for_each_sgtable_sg(sgt, sg, i) \
158 for_each_sg((sgt)->sgl, sg, (sgt)->orig_nents, i)
159
160/*
161 * Loop over each sg element in the given *DMA mapped* sg_table object.
162 * Please use sg_dma_address(sg) and sg_dma_len(sg) to extract DMA addresses
163 * of the each element.
164 */
165#define for_each_sgtable_dma_sg(sgt, sg, i) \
166 for_each_sg((sgt)->sgl, sg, (sgt)->nents, i)
167
168/**
169 * sg_chain - Chain two sglists together
170 * @prv: First scatterlist
171 * @prv_nents: Number of entries in prv
172 * @sgl: Second scatterlist
173 *
174 * Description:
175 * Links @prv@ and @sgl@ together, to form a longer scatterlist.
176 *
177 **/
178static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
179 struct scatterlist *sgl)
180{
181 /*
182 * offset and length are unused for chain entry. Clear them.
183 */
184 prv[prv_nents - 1].offset = 0;
185 prv[prv_nents - 1].length = 0;
186
187 /*
188 * Set lowest bit to indicate a link pointer, and make sure to clear
189 * the termination bit if it happens to be set.
190 */
191 prv[prv_nents - 1].page_link = ((unsigned long) sgl | SG_CHAIN)
192 & ~SG_END;
193}
194
195/**
196 * sg_mark_end - Mark the end of the scatterlist
197 * @sg: SG entryScatterlist
198 *
199 * Description:
200 * Marks the passed in sg entry as the termination point for the sg
201 * table. A call to sg_next() on this entry will return NULL.
202 *
203 **/
204static inline void sg_mark_end(struct scatterlist *sg)
205{
206 /*
207 * Set termination bit, clear potential chain bit
208 */
209 sg->page_link |= SG_END;
210 sg->page_link &= ~SG_CHAIN;
211}
212
213/**
214 * sg_unmark_end - Undo setting the end of the scatterlist
215 * @sg: SG entryScatterlist
216 *
217 * Description:
218 * Removes the termination marker from the given entry of the scatterlist.
219 *
220 **/
221static inline void sg_unmark_end(struct scatterlist *sg)
222{
223 sg->page_link &= ~SG_END;
224}
225
226/**
227 * sg_phys - Return physical address of an sg entry
228 * @sg: SG entry
229 *
230 * Description:
231 * This calls page_to_phys() on the page in this sg entry, and adds the
232 * sg offset. The caller must know that it is legal to call page_to_phys()
233 * on the sg page.
234 *
235 **/
236static inline dma_addr_t sg_phys(struct scatterlist *sg)
237{
238 return page_to_phys(sg_page(sg)) + sg->offset;
239}
240
241/**
242 * sg_virt - Return virtual address of an sg entry
243 * @sg: SG entry
244 *
245 * Description:
246 * This calls page_address() on the page in this sg entry, and adds the
247 * sg offset. The caller must know that the sg page has a valid virtual
248 * mapping.
249 *
250 **/
251static inline void *sg_virt(struct scatterlist *sg)
252{
253 return page_address(sg_page(sg)) + sg->offset;
254}
255
256/**
257 * sg_init_marker - Initialize markers in sg table
258 * @sgl: The SG table
259 * @nents: Number of entries in table
260 *
261 **/
262static inline void sg_init_marker(struct scatterlist *sgl,
263 unsigned int nents)
264{
265 sg_mark_end(&sgl[nents - 1]);
266}
267
268int sg_nents(struct scatterlist *sg);
269int sg_nents_for_len(struct scatterlist *sg, u64 len);
270struct scatterlist *sg_next(struct scatterlist *);
271struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
272void sg_init_table(struct scatterlist *, unsigned int);
273void sg_init_one(struct scatterlist *, const void *, unsigned int);
274int sg_split(struct scatterlist *in, const int in_mapped_nents,
275 const off_t skip, const int nb_splits,
276 const size_t *split_sizes,
277 struct scatterlist **out, int *out_mapped_nents,
278 gfp_t gfp_mask);
279
280typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
281typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
282
283void __sg_free_table(struct sg_table *, unsigned int, unsigned int,
284 sg_free_fn *);
285void sg_free_table(struct sg_table *);
286int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
287 struct scatterlist *, unsigned int, gfp_t, sg_alloc_fn *);
288int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
289int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
290 unsigned int n_pages, unsigned int offset,
291 unsigned long size, unsigned int max_segment,
292 gfp_t gfp_mask);
293int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
294 unsigned int n_pages, unsigned int offset,
295 unsigned long size, gfp_t gfp_mask);
296
297#ifdef CONFIG_SGL_ALLOC
298struct scatterlist *sgl_alloc_order(unsigned long long length,
299 unsigned int order, bool chainable,
300 gfp_t gfp, unsigned int *nent_p);
301struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
302 unsigned int *nent_p);
303void sgl_free_n_order(struct scatterlist *sgl, int nents, int order);
304void sgl_free_order(struct scatterlist *sgl, int order);
305void sgl_free(struct scatterlist *sgl);
306#endif /* CONFIG_SGL_ALLOC */
307
308size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
309 size_t buflen, off_t skip, bool to_buffer);
310
311size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
312 const void *buf, size_t buflen);
313size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
314 void *buf, size_t buflen);
315
316size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
317 const void *buf, size_t buflen, off_t skip);
318size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
319 void *buf, size_t buflen, off_t skip);
320size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
321 size_t buflen, off_t skip);
322
323/*
324 * Maximum number of entries that will be allocated in one piece, if
325 * a list larger than this is required then chaining will be utilized.
326 */
327#define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
328
329/*
330 * The maximum number of SG segments that we will put inside a
331 * scatterlist (unless chaining is used). Should ideally fit inside a
332 * single page, to avoid a higher order allocation. We could define this
333 * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order. The
334 * minimum value is 32
335 */
336#define SG_CHUNK_SIZE 128
337
338/*
339 * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
340 * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
341 */
342#ifdef CONFIG_ARCH_NO_SG_CHAIN
343#define SG_MAX_SEGMENTS SG_CHUNK_SIZE
344#else
345#define SG_MAX_SEGMENTS 2048
346#endif
347
348#ifdef CONFIG_SG_POOL
349void sg_free_table_chained(struct sg_table *table,
350 unsigned nents_first_chunk);
351int sg_alloc_table_chained(struct sg_table *table, int nents,
352 struct scatterlist *first_chunk,
353 unsigned nents_first_chunk);
354#endif
355
356/*
357 * sg page iterator
358 *
359 * Iterates over sg entries page-by-page. On each successful iteration, you
360 * can call sg_page_iter_page(@piter) to get the current page.
361 * @piter->sg will point to the sg holding this page and @piter->sg_pgoffset to
362 * the page's page offset within the sg. The iteration will stop either when a
363 * maximum number of sg entries was reached or a terminating sg
364 * (sg_last(sg) == true) was reached.
365 */
366struct sg_page_iter {
367 struct scatterlist *sg; /* sg holding the page */
368 unsigned int sg_pgoffset; /* page offset within the sg */
369
370 /* these are internal states, keep away */
371 unsigned int __nents; /* remaining sg entries */
372 int __pg_advance; /* nr pages to advance at the
373 * next step */
374};
375
376/*
377 * sg page iterator for DMA addresses
378 *
379 * This is the same as sg_page_iter however you can call
380 * sg_page_iter_dma_address(@dma_iter) to get the page's DMA
381 * address. sg_page_iter_page() cannot be called on this iterator.
382 */
383struct sg_dma_page_iter {
384 struct sg_page_iter base;
385};
386
387bool __sg_page_iter_next(struct sg_page_iter *piter);
388bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter);
389void __sg_page_iter_start(struct sg_page_iter *piter,
390 struct scatterlist *sglist, unsigned int nents,
391 unsigned long pgoffset);
392/**
393 * sg_page_iter_page - get the current page held by the page iterator
394 * @piter: page iterator holding the page
395 */
396static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
397{
398 return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
399}
400
401/**
402 * sg_page_iter_dma_address - get the dma address of the current page held by
403 * the page iterator.
404 * @dma_iter: page iterator holding the page
405 */
406static inline dma_addr_t
407sg_page_iter_dma_address(struct sg_dma_page_iter *dma_iter)
408{
409 return sg_dma_address(dma_iter->base.sg) +
410 (dma_iter->base.sg_pgoffset << PAGE_SHIFT);
411}
412
413/**
414 * for_each_sg_page - iterate over the pages of the given sg list
415 * @sglist: sglist to iterate over
416 * @piter: page iterator to hold current page, sg, sg_pgoffset
417 * @nents: maximum number of sg entries to iterate over
418 * @pgoffset: starting page offset (in pages)
419 *
420 * Callers may use sg_page_iter_page() to get each page pointer.
421 * In each loop it operates on PAGE_SIZE unit.
422 */
423#define for_each_sg_page(sglist, piter, nents, pgoffset) \
424 for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
425 __sg_page_iter_next(piter);)
426
427/**
428 * for_each_sg_dma_page - iterate over the pages of the given sg list
429 * @sglist: sglist to iterate over
430 * @dma_iter: DMA page iterator to hold current page
431 * @dma_nents: maximum number of sg entries to iterate over, this is the value
432 * returned from dma_map_sg
433 * @pgoffset: starting page offset (in pages)
434 *
435 * Callers may use sg_page_iter_dma_address() to get each page's DMA address.
436 * In each loop it operates on PAGE_SIZE unit.
437 */
438#define for_each_sg_dma_page(sglist, dma_iter, dma_nents, pgoffset) \
439 for (__sg_page_iter_start(&(dma_iter)->base, sglist, dma_nents, \
440 pgoffset); \
441 __sg_page_iter_dma_next(dma_iter);)
442
443/**
444 * for_each_sgtable_page - iterate over all pages in the sg_table object
445 * @sgt: sg_table object to iterate over
446 * @piter: page iterator to hold current page
447 * @pgoffset: starting page offset (in pages)
448 *
449 * Iterates over the all memory pages in the buffer described by
450 * a scatterlist stored in the given sg_table object.
451 * See also for_each_sg_page(). In each loop it operates on PAGE_SIZE unit.
452 */
453#define for_each_sgtable_page(sgt, piter, pgoffset) \
454 for_each_sg_page((sgt)->sgl, piter, (sgt)->orig_nents, pgoffset)
455
456/**
457 * for_each_sgtable_dma_page - iterate over the DMA mapped sg_table object
458 * @sgt: sg_table object to iterate over
459 * @dma_iter: DMA page iterator to hold current page
460 * @pgoffset: starting page offset (in pages)
461 *
462 * Iterates over the all DMA mapped pages in the buffer described by
463 * a scatterlist stored in the given sg_table object.
464 * See also for_each_sg_dma_page(). In each loop it operates on PAGE_SIZE
465 * unit.
466 */
467#define for_each_sgtable_dma_page(sgt, dma_iter, pgoffset) \
468 for_each_sg_dma_page((sgt)->sgl, dma_iter, (sgt)->nents, pgoffset)
469
470
471/*
472 * Mapping sg iterator
473 *
474 * Iterates over sg entries mapping page-by-page. On each successful
475 * iteration, @miter->page points to the mapped page and
476 * @miter->length bytes of data can be accessed at @miter->addr. As
477 * long as an interation is enclosed between start and stop, the user
478 * is free to choose control structure and when to stop.
479 *
480 * @miter->consumed is set to @miter->length on each iteration. It
481 * can be adjusted if the user can't consume all the bytes in one go.
482 * Also, a stopped iteration can be resumed by calling next on it.
483 * This is useful when iteration needs to release all resources and
484 * continue later (e.g. at the next interrupt).
485 */
486
487#define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */
488#define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */
489#define SG_MITER_FROM_SG (1 << 2) /* nop */
490
491struct sg_mapping_iter {
492 /* the following three fields can be accessed directly */
493 struct page *page; /* currently mapped page */
494 void *addr; /* pointer to the mapped area */
495 size_t length; /* length of the mapped area */
496 size_t consumed; /* number of consumed bytes */
497 struct sg_page_iter piter; /* page iterator */
498
499 /* these are internal states, keep away */
500 unsigned int __offset; /* offset within page */
501 unsigned int __remaining; /* remaining bytes on page */
502 unsigned int __flags;
503};
504
505void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
506 unsigned int nents, unsigned int flags);
507bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
508bool sg_miter_next(struct sg_mapping_iter *miter);
509void sg_miter_stop(struct sg_mapping_iter *miter);
510
511#endif /* _LINUX_SCATTERLIST_H */
1#ifndef _LINUX_SCATTERLIST_H
2#define _LINUX_SCATTERLIST_H
3
4#include <linux/string.h>
5#include <linux/bug.h>
6#include <linux/mm.h>
7
8#include <asm/types.h>
9#include <asm/scatterlist.h>
10#include <asm/io.h>
11
12struct sg_table {
13 struct scatterlist *sgl; /* the list */
14 unsigned int nents; /* number of mapped entries */
15 unsigned int orig_nents; /* original size of list */
16};
17
18/*
19 * Notes on SG table design.
20 *
21 * Architectures must provide an unsigned long page_link field in the
22 * scatterlist struct. We use that to place the page pointer AND encode
23 * information about the sg table as well. The two lower bits are reserved
24 * for this information.
25 *
26 * If bit 0 is set, then the page_link contains a pointer to the next sg
27 * table list. Otherwise the next entry is at sg + 1.
28 *
29 * If bit 1 is set, then this sg entry is the last element in a list.
30 *
31 * See sg_next().
32 *
33 */
34
35#define SG_MAGIC 0x87654321
36
37/*
38 * We overload the LSB of the page pointer to indicate whether it's
39 * a valid sg entry, or whether it points to the start of a new scatterlist.
40 * Those low bits are there for everyone! (thanks mason :-)
41 */
42#define sg_is_chain(sg) ((sg)->page_link & 0x01)
43#define sg_is_last(sg) ((sg)->page_link & 0x02)
44#define sg_chain_ptr(sg) \
45 ((struct scatterlist *) ((sg)->page_link & ~0x03))
46
47/**
48 * sg_assign_page - Assign a given page to an SG entry
49 * @sg: SG entry
50 * @page: The page
51 *
52 * Description:
53 * Assign page to sg entry. Also see sg_set_page(), the most commonly used
54 * variant.
55 *
56 **/
57static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
58{
59 unsigned long page_link = sg->page_link & 0x3;
60
61 /*
62 * In order for the low bit stealing approach to work, pages
63 * must be aligned at a 32-bit boundary as a minimum.
64 */
65 BUG_ON((unsigned long) page & 0x03);
66#ifdef CONFIG_DEBUG_SG
67 BUG_ON(sg->sg_magic != SG_MAGIC);
68 BUG_ON(sg_is_chain(sg));
69#endif
70 sg->page_link = page_link | (unsigned long) page;
71}
72
73/**
74 * sg_set_page - Set sg entry to point at given page
75 * @sg: SG entry
76 * @page: The page
77 * @len: Length of data
78 * @offset: Offset into page
79 *
80 * Description:
81 * Use this function to set an sg entry pointing at a page, never assign
82 * the page directly. We encode sg table information in the lower bits
83 * of the page pointer. See sg_page() for looking up the page belonging
84 * to an sg entry.
85 *
86 **/
87static inline void sg_set_page(struct scatterlist *sg, struct page *page,
88 unsigned int len, unsigned int offset)
89{
90 sg_assign_page(sg, page);
91 sg->offset = offset;
92 sg->length = len;
93}
94
95static inline struct page *sg_page(struct scatterlist *sg)
96{
97#ifdef CONFIG_DEBUG_SG
98 BUG_ON(sg->sg_magic != SG_MAGIC);
99 BUG_ON(sg_is_chain(sg));
100#endif
101 return (struct page *)((sg)->page_link & ~0x3);
102}
103
104/**
105 * sg_set_buf - Set sg entry to point at given data
106 * @sg: SG entry
107 * @buf: Data
108 * @buflen: Data length
109 *
110 **/
111static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
112 unsigned int buflen)
113{
114 sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
115}
116
117/*
118 * Loop over each sg element, following the pointer to a new list if necessary
119 */
120#define for_each_sg(sglist, sg, nr, __i) \
121 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
122
123/**
124 * sg_chain - Chain two sglists together
125 * @prv: First scatterlist
126 * @prv_nents: Number of entries in prv
127 * @sgl: Second scatterlist
128 *
129 * Description:
130 * Links @prv@ and @sgl@ together, to form a longer scatterlist.
131 *
132 **/
133static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
134 struct scatterlist *sgl)
135{
136#ifndef ARCH_HAS_SG_CHAIN
137 BUG();
138#endif
139
140 /*
141 * offset and length are unused for chain entry. Clear them.
142 */
143 prv[prv_nents - 1].offset = 0;
144 prv[prv_nents - 1].length = 0;
145
146 /*
147 * Set lowest bit to indicate a link pointer, and make sure to clear
148 * the termination bit if it happens to be set.
149 */
150 prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
151}
152
153/**
154 * sg_mark_end - Mark the end of the scatterlist
155 * @sg: SG entryScatterlist
156 *
157 * Description:
158 * Marks the passed in sg entry as the termination point for the sg
159 * table. A call to sg_next() on this entry will return NULL.
160 *
161 **/
162static inline void sg_mark_end(struct scatterlist *sg)
163{
164#ifdef CONFIG_DEBUG_SG
165 BUG_ON(sg->sg_magic != SG_MAGIC);
166#endif
167 /*
168 * Set termination bit, clear potential chain bit
169 */
170 sg->page_link |= 0x02;
171 sg->page_link &= ~0x01;
172}
173
174/**
175 * sg_phys - Return physical address of an sg entry
176 * @sg: SG entry
177 *
178 * Description:
179 * This calls page_to_phys() on the page in this sg entry, and adds the
180 * sg offset. The caller must know that it is legal to call page_to_phys()
181 * on the sg page.
182 *
183 **/
184static inline dma_addr_t sg_phys(struct scatterlist *sg)
185{
186 return page_to_phys(sg_page(sg)) + sg->offset;
187}
188
189/**
190 * sg_virt - Return virtual address of an sg entry
191 * @sg: SG entry
192 *
193 * Description:
194 * This calls page_address() on the page in this sg entry, and adds the
195 * sg offset. The caller must know that the sg page has a valid virtual
196 * mapping.
197 *
198 **/
199static inline void *sg_virt(struct scatterlist *sg)
200{
201 return page_address(sg_page(sg)) + sg->offset;
202}
203
204struct scatterlist *sg_next(struct scatterlist *);
205struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
206void sg_init_table(struct scatterlist *, unsigned int);
207void sg_init_one(struct scatterlist *, const void *, unsigned int);
208
209typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
210typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
211
212void __sg_free_table(struct sg_table *, unsigned int, sg_free_fn *);
213void sg_free_table(struct sg_table *);
214int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, gfp_t,
215 sg_alloc_fn *);
216int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
217
218size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
219 void *buf, size_t buflen);
220size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
221 void *buf, size_t buflen);
222
223/*
224 * Maximum number of entries that will be allocated in one piece, if
225 * a list larger than this is required then chaining will be utilized.
226 */
227#define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
228
229
230/*
231 * Mapping sg iterator
232 *
233 * Iterates over sg entries mapping page-by-page. On each successful
234 * iteration, @miter->page points to the mapped page and
235 * @miter->length bytes of data can be accessed at @miter->addr. As
236 * long as an interation is enclosed between start and stop, the user
237 * is free to choose control structure and when to stop.
238 *
239 * @miter->consumed is set to @miter->length on each iteration. It
240 * can be adjusted if the user can't consume all the bytes in one go.
241 * Also, a stopped iteration can be resumed by calling next on it.
242 * This is useful when iteration needs to release all resources and
243 * continue later (e.g. at the next interrupt).
244 */
245
246#define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */
247#define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */
248#define SG_MITER_FROM_SG (1 << 2) /* nop */
249
250struct sg_mapping_iter {
251 /* the following three fields can be accessed directly */
252 struct page *page; /* currently mapped page */
253 void *addr; /* pointer to the mapped area */
254 size_t length; /* length of the mapped area */
255 size_t consumed; /* number of consumed bytes */
256
257 /* these are internal states, keep away */
258 struct scatterlist *__sg; /* current entry */
259 unsigned int __nents; /* nr of remaining entries */
260 unsigned int __offset; /* offset within sg */
261 unsigned int __flags;
262};
263
264void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
265 unsigned int nents, unsigned int flags);
266bool sg_miter_next(struct sg_mapping_iter *miter);
267void sg_miter_stop(struct sg_mapping_iter *miter);
268
269#endif /* _LINUX_SCATTERLIST_H */