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 * 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 **/
164static 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 **/
190static 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 **/
207static 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 **/
222static 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 **/
237static 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 **/
248static inline void sg_init_marker(struct scatterlist *sgl,
249 unsigned int nents)
250{
251 sg_mark_end(&sgl[nents - 1]);
252}
253
254int sg_nents(struct scatterlist *sg);
255int sg_nents_for_len(struct scatterlist *sg, u64 len);
256struct scatterlist *sg_next(struct scatterlist *);
257struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
258void sg_init_table(struct scatterlist *, unsigned int);
259void sg_init_one(struct scatterlist *, const void *, unsigned int);
260int 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
266typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
267typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
268
269void __sg_free_table(struct sg_table *, unsigned int, bool, sg_free_fn *);
270void sg_free_table(struct sg_table *);
271int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
272 struct scatterlist *, gfp_t, sg_alloc_fn *);
273int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
274int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
275 unsigned int n_pages, unsigned int offset,
276 unsigned long size, unsigned int max_segment,
277 gfp_t gfp_mask);
278int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
279 unsigned int n_pages, unsigned int offset,
280 unsigned long size, gfp_t gfp_mask);
281
282#ifdef CONFIG_SGL_ALLOC
283struct scatterlist *sgl_alloc_order(unsigned long long length,
284 unsigned int order, bool chainable,
285 gfp_t gfp, unsigned int *nent_p);
286struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
287 unsigned int *nent_p);
288void sgl_free_n_order(struct scatterlist *sgl, int nents, int order);
289void sgl_free_order(struct scatterlist *sgl, int order);
290void sgl_free(struct scatterlist *sgl);
291#endif /* CONFIG_SGL_ALLOC */
292
293size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
294 size_t buflen, off_t skip, bool to_buffer);
295
296size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
297 const void *buf, size_t buflen);
298size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
299 void *buf, size_t buflen);
300
301size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
302 const void *buf, size_t buflen, off_t skip);
303size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
304 void *buf, size_t buflen, off_t skip);
305size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
306 size_t buflen, off_t skip);
307
308/*
309 * Maximum number of entries that will be allocated in one piece, if
310 * a list larger than this is required then chaining will be utilized.
311 */
312#define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
313
314/*
315 * The maximum number of SG segments that we will put inside a
316 * scatterlist (unless chaining is used). Should ideally fit inside a
317 * single page, to avoid a higher order allocation. We could define this
318 * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order. The
319 * minimum value is 32
320 */
321#define SG_CHUNK_SIZE 128
322
323/*
324 * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
325 * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
326 */
327#ifdef CONFIG_ARCH_HAS_SG_CHAIN
328#define SG_MAX_SEGMENTS 2048
329#else
330#define SG_MAX_SEGMENTS SG_CHUNK_SIZE
331#endif
332
333#ifdef CONFIG_SG_POOL
334void sg_free_table_chained(struct sg_table *table, bool first_chunk);
335int sg_alloc_table_chained(struct sg_table *table, int nents,
336 struct scatterlist *first_chunk);
337#endif
338
339/*
340 * sg page iterator
341 *
342 * Iterates over sg entries page-by-page. On each successful iteration,
343 * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
344 * to get the current page and its dma address. @piter->sg will point to the
345 * sg holding this page and @piter->sg_pgoffset to the page's page offset
346 * within the sg. The iteration will stop either when a maximum number of sg
347 * entries was reached or a terminating sg (sg_last(sg) == true) was reached.
348 */
349struct sg_page_iter {
350 struct scatterlist *sg; /* sg holding the page */
351 unsigned int sg_pgoffset; /* page offset within the sg */
352
353 /* these are internal states, keep away */
354 unsigned int __nents; /* remaining sg entries */
355 int __pg_advance; /* nr pages to advance at the
356 * next step */
357};
358
359bool __sg_page_iter_next(struct sg_page_iter *piter);
360void __sg_page_iter_start(struct sg_page_iter *piter,
361 struct scatterlist *sglist, unsigned int nents,
362 unsigned long pgoffset);
363/**
364 * sg_page_iter_page - get the current page held by the page iterator
365 * @piter: page iterator holding the page
366 */
367static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
368{
369 return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
370}
371
372/**
373 * sg_page_iter_dma_address - get the dma address of the current page held by
374 * the page iterator.
375 * @piter: page iterator holding the page
376 */
377static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter)
378{
379 return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT);
380}
381
382/**
383 * for_each_sg_page - iterate over the pages of the given sg list
384 * @sglist: sglist to iterate over
385 * @piter: page iterator to hold current page, sg, sg_pgoffset
386 * @nents: maximum number of sg entries to iterate over
387 * @pgoffset: starting page offset
388 */
389#define for_each_sg_page(sglist, piter, nents, pgoffset) \
390 for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
391 __sg_page_iter_next(piter);)
392
393/*
394 * Mapping sg iterator
395 *
396 * Iterates over sg entries mapping page-by-page. On each successful
397 * iteration, @miter->page points to the mapped page and
398 * @miter->length bytes of data can be accessed at @miter->addr. As
399 * long as an interation is enclosed between start and stop, the user
400 * is free to choose control structure and when to stop.
401 *
402 * @miter->consumed is set to @miter->length on each iteration. It
403 * can be adjusted if the user can't consume all the bytes in one go.
404 * Also, a stopped iteration can be resumed by calling next on it.
405 * This is useful when iteration needs to release all resources and
406 * continue later (e.g. at the next interrupt).
407 */
408
409#define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */
410#define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */
411#define SG_MITER_FROM_SG (1 << 2) /* nop */
412
413struct sg_mapping_iter {
414 /* the following three fields can be accessed directly */
415 struct page *page; /* currently mapped page */
416 void *addr; /* pointer to the mapped area */
417 size_t length; /* length of the mapped area */
418 size_t consumed; /* number of consumed bytes */
419 struct sg_page_iter piter; /* page iterator */
420
421 /* these are internal states, keep away */
422 unsigned int __offset; /* offset within page */
423 unsigned int __remaining; /* remaining bytes on page */
424 unsigned int __flags;
425};
426
427void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
428 unsigned int nents, unsigned int flags);
429bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
430bool sg_miter_next(struct sg_mapping_iter *miter);
431void sg_miter_stop(struct sg_mapping_iter *miter);
432
433#endif /* _LINUX_SCATTERLIST_H */
434