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, unsigned int,
270 sg_free_fn *);
271 void sg_free_table(struct sg_table *);
272 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
273 struct scatterlist *, unsigned int, gfp_t, sg_alloc_fn *);
274 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
275 int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
276 unsigned int n_pages, unsigned int offset,
277 unsigned long size, unsigned int max_segment,
278 gfp_t gfp_mask);
279 int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
280 unsigned int n_pages, unsigned int offset,
281 unsigned long size, gfp_t gfp_mask);
282
283 #ifdef CONFIG_SGL_ALLOC
284 struct scatterlist *sgl_alloc_order(unsigned long long length,
285 unsigned int order, bool chainable,
286 gfp_t gfp, unsigned int *nent_p);
287 struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
288 unsigned int *nent_p);
289 void sgl_free_n_order(struct scatterlist *sgl, int nents, int order);
290 void sgl_free_order(struct scatterlist *sgl, int order);
291 void sgl_free(struct scatterlist *sgl);
292 #endif /* CONFIG_SGL_ALLOC */
293
294 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
295 size_t buflen, off_t skip, bool to_buffer);
296
297 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
298 const void *buf, size_t buflen);
299 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
300 void *buf, size_t buflen);
301
302 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
303 const void *buf, size_t buflen, off_t skip);
304 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
305 void *buf, size_t buflen, off_t skip);
306 size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
307 size_t buflen, off_t skip);
308
309 /*
310 * Maximum number of entries that will be allocated in one piece, if
311 * a list larger than this is required then chaining will be utilized.
312 */
313 #define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
314
315 /*
316 * The maximum number of SG segments that we will put inside a
317 * scatterlist (unless chaining is used). Should ideally fit inside a
318 * single page, to avoid a higher order allocation. We could define this
319 * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order. The
320 * minimum value is 32
321 */
322 #define SG_CHUNK_SIZE 128
323
324 /*
325 * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
326 * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
327 */
328 #ifdef CONFIG_ARCH_NO_SG_CHAIN
329 #define SG_MAX_SEGMENTS SG_CHUNK_SIZE
330 #else
331 #define SG_MAX_SEGMENTS 2048
332 #endif
333
334 #ifdef CONFIG_SG_POOL
335 void sg_free_table_chained(struct sg_table *table,
336 unsigned nents_first_chunk);
337 int sg_alloc_table_chained(struct sg_table *table, int nents,
338 struct scatterlist *first_chunk,
339 unsigned nents_first_chunk);
340 #endif
341
342 /*
343 * sg page iterator
344 *
345 * Iterates over sg entries page-by-page. On each successful iteration, you
346 * can call sg_page_iter_page(@piter) to get the current page.
347 * @piter->sg will point to the sg holding this page and @piter->sg_pgoffset to
348 * the page's page offset within the sg. The iteration will stop either when a
349 * maximum number of sg entries was reached or a terminating sg
350 * (sg_last(sg) == true) was reached.
351 */
352 struct sg_page_iter {
353 struct scatterlist *sg; /* sg holding the page */
354 unsigned int sg_pgoffset; /* page offset within the sg */
355
356 /* these are internal states, keep away */
357 unsigned int __nents; /* remaining sg entries */
358 int __pg_advance; /* nr pages to advance at the
359 * next step */
360 };
361
362 /*
363 * sg page iterator for DMA addresses
364 *
365 * This is the same as sg_page_iter however you can call
366 * sg_page_iter_dma_address(@dma_iter) to get the page's DMA
367 * address. sg_page_iter_page() cannot be called on this iterator.
368 */
369 struct sg_dma_page_iter {
370 struct sg_page_iter base;
371 };
372
373 bool __sg_page_iter_next(struct sg_page_iter *piter);
374 bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter);
375 void __sg_page_iter_start(struct sg_page_iter *piter,
376 struct scatterlist *sglist, unsigned int nents,
377 unsigned long pgoffset);
378 /**
379 * sg_page_iter_page - get the current page held by the page iterator
380 * @piter: page iterator holding the page
381 */
382 static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
383 {
384 return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
385 }
386
387 /**
388 * sg_page_iter_dma_address - get the dma address of the current page held by
389 * the page iterator.
390 * @dma_iter: page iterator holding the page
391 */
392 static inline dma_addr_t
393 sg_page_iter_dma_address(struct sg_dma_page_iter *dma_iter)
394 {
395 return sg_dma_address(dma_iter->base.sg) +
396 (dma_iter->base.sg_pgoffset << PAGE_SHIFT);
397 }
398
399 /**
400 * for_each_sg_page - iterate over the pages of the given sg list
401 * @sglist: sglist to iterate over
402 * @piter: page iterator to hold current page, sg, sg_pgoffset
403 * @nents: maximum number of sg entries to iterate over
404 * @pgoffset: starting page offset
405 *
406 * Callers may use sg_page_iter_page() to get each page pointer.
407 */
408 #define for_each_sg_page(sglist, piter, nents, pgoffset) \
409 for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
410 __sg_page_iter_next(piter);)
411
412 /**
413 * for_each_sg_dma_page - iterate over the pages of the given sg list
414 * @sglist: sglist to iterate over
415 * @dma_iter: page iterator to hold current page
416 * @dma_nents: maximum number of sg entries to iterate over, this is the value
417 * returned from dma_map_sg
418 * @pgoffset: starting page offset
419 *
420 * Callers may use sg_page_iter_dma_address() to get each page's DMA address.
421 */
422 #define for_each_sg_dma_page(sglist, dma_iter, dma_nents, pgoffset) \
423 for (__sg_page_iter_start(&(dma_iter)->base, sglist, dma_nents, \
424 pgoffset); \
425 __sg_page_iter_dma_next(dma_iter);)
426
427 /*
428 * Mapping sg iterator
429 *
430 * Iterates over sg entries mapping page-by-page. On each successful
431 * iteration, @miter->page points to the mapped page and
432 * @miter->length bytes of data can be accessed at @miter->addr. As
433 * long as an interation is enclosed between start and stop, the user
434 * is free to choose control structure and when to stop.
435 *
436 * @miter->consumed is set to @miter->length on each iteration. It
437 * can be adjusted if the user can't consume all the bytes in one go.
438 * Also, a stopped iteration can be resumed by calling next on it.
439 * This is useful when iteration needs to release all resources and
440 * continue later (e.g. at the next interrupt).
441 */
442
443 #define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */
444 #define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */
445 #define SG_MITER_FROM_SG (1 << 2) /* nop */
446
447 struct sg_mapping_iter {
448 /* the following three fields can be accessed directly */
449 struct page *page; /* currently mapped page */
450 void *addr; /* pointer to the mapped area */
451 size_t length; /* length of the mapped area */
452 size_t consumed; /* number of consumed bytes */
453 struct sg_page_iter piter; /* page iterator */
454
455 /* these are internal states, keep away */
456 unsigned int __offset; /* offset within page */
457 unsigned int __remaining; /* remaining bytes on page */
458 unsigned int __flags;
459 };
460
461 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
462 unsigned int nents, unsigned int flags);
463 bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
464 bool sg_miter_next(struct sg_mapping_iter *miter);
465 void sg_miter_stop(struct sg_mapping_iter *miter);
466
467 #endif /* _LINUX_SCATTERLIST_H */
468
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