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1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_SCATTERLIST_H
3 #define _LINUX_SCATTERLIST_H
5 #include <linux/string.h>
6 #include <linux/types.h>
12 #ifdef CONFIG_DEBUG_SG
13 unsigned long sg_magic
;
15 unsigned long page_link
;
18 dma_addr_t dma_address
;
19 #ifdef CONFIG_NEED_SG_DMA_LENGTH
20 unsigned int dma_length
;
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
31 #define sg_dma_address(sg) ((sg)->dma_address)
33 #ifdef CONFIG_NEED_SG_DMA_LENGTH
34 #define sg_dma_len(sg) ((sg)->dma_length)
36 #define sg_dma_len(sg) ((sg)->length)
40 struct scatterlist
*sgl
; /* the list */
41 unsigned int nents
; /* number of mapped entries */
42 unsigned int orig_nents
; /* original size of list */
46 * Notes on SG table design.
48 * We use the unsigned long page_link field in the scatterlist struct to place
49 * the page pointer AND encode information about the sg table as well. The two
50 * lower bits are reserved for this information.
52 * If bit 0 is set, then the page_link contains a pointer to the next sg
53 * table list. Otherwise the next entry is at sg + 1.
55 * If bit 1 is set, then this sg entry is the last element in a list.
61 #define SG_MAGIC 0x87654321
64 * We overload the LSB of the page pointer to indicate whether it's
65 * a valid sg entry, or whether it points to the start of a new scatterlist.
66 * Those low bits are there for everyone! (thanks mason :-)
68 #define sg_is_chain(sg) ((sg)->page_link & 0x01)
69 #define sg_is_last(sg) ((sg)->page_link & 0x02)
70 #define sg_chain_ptr(sg) \
71 ((struct scatterlist *) ((sg)->page_link & ~0x03))
74 * sg_assign_page - Assign a given page to an SG entry
79 * Assign page to sg entry. Also see sg_set_page(), the most commonly used
83 static inline void sg_assign_page(struct scatterlist
*sg
, struct page
*page
)
85 unsigned long page_link
= sg
->page_link
& 0x3;
88 * In order for the low bit stealing approach to work, pages
89 * must be aligned at a 32-bit boundary as a minimum.
91 BUG_ON((unsigned long) page
& 0x03);
92 #ifdef CONFIG_DEBUG_SG
93 BUG_ON(sg
->sg_magic
!= SG_MAGIC
);
94 BUG_ON(sg_is_chain(sg
));
96 sg
->page_link
= page_link
| (unsigned long) page
;
100 * sg_set_page - Set sg entry to point at given page
103 * @len: Length of data
104 * @offset: Offset into page
107 * Use this function to set an sg entry pointing at a page, never assign
108 * the page directly. We encode sg table information in the lower bits
109 * of the page pointer. See sg_page() for looking up the page belonging
113 static inline void sg_set_page(struct scatterlist
*sg
, struct page
*page
,
114 unsigned int len
, unsigned int offset
)
116 sg_assign_page(sg
, page
);
121 static inline struct page
*sg_page(struct scatterlist
*sg
)
123 #ifdef CONFIG_DEBUG_SG
124 BUG_ON(sg
->sg_magic
!= SG_MAGIC
);
125 BUG_ON(sg_is_chain(sg
));
127 return (struct page
*)((sg
)->page_link
& ~0x3);
131 * sg_set_buf - Set sg entry to point at given data
134 * @buflen: Data length
137 static inline void sg_set_buf(struct scatterlist
*sg
, const void *buf
,
140 #ifdef CONFIG_DEBUG_SG
141 BUG_ON(!virt_addr_valid(buf
));
143 sg_set_page(sg
, virt_to_page(buf
), buflen
, offset_in_page(buf
));
147 * Loop over each sg element, following the pointer to a new list if necessary
149 #define for_each_sg(sglist, sg, nr, __i) \
150 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
153 * sg_chain - Chain two sglists together
154 * @prv: First scatterlist
155 * @prv_nents: Number of entries in prv
156 * @sgl: Second scatterlist
159 * Links @prv@ and @sgl@ together, to form a longer scatterlist.
162 static inline void sg_chain(struct scatterlist
*prv
, unsigned int prv_nents
,
163 struct scatterlist
*sgl
)
166 * offset and length are unused for chain entry. Clear them.
168 prv
[prv_nents
- 1].offset
= 0;
169 prv
[prv_nents
- 1].length
= 0;
172 * Set lowest bit to indicate a link pointer, and make sure to clear
173 * the termination bit if it happens to be set.
175 prv
[prv_nents
- 1].page_link
= ((unsigned long) sgl
| 0x01) & ~0x02;
179 * sg_mark_end - Mark the end of the scatterlist
180 * @sg: SG entryScatterlist
183 * Marks the passed in sg entry as the termination point for the sg
184 * table. A call to sg_next() on this entry will return NULL.
187 static inline void sg_mark_end(struct scatterlist
*sg
)
189 #ifdef CONFIG_DEBUG_SG
190 BUG_ON(sg
->sg_magic
!= SG_MAGIC
);
193 * Set termination bit, clear potential chain bit
195 sg
->page_link
|= 0x02;
196 sg
->page_link
&= ~0x01;
200 * sg_unmark_end - Undo setting the end of the scatterlist
201 * @sg: SG entryScatterlist
204 * Removes the termination marker from the given entry of the scatterlist.
207 static inline void sg_unmark_end(struct scatterlist
*sg
)
209 #ifdef CONFIG_DEBUG_SG
210 BUG_ON(sg
->sg_magic
!= SG_MAGIC
);
212 sg
->page_link
&= ~0x02;
216 * sg_phys - Return physical address of an sg entry
220 * This calls page_to_phys() on the page in this sg entry, and adds the
221 * sg offset. The caller must know that it is legal to call page_to_phys()
225 static inline dma_addr_t
sg_phys(struct scatterlist
*sg
)
227 return page_to_phys(sg_page(sg
)) + sg
->offset
;
231 * sg_virt - Return virtual address of an sg entry
235 * This calls page_address() on the page in this sg entry, and adds the
236 * sg offset. The caller must know that the sg page has a valid virtual
240 static inline void *sg_virt(struct scatterlist
*sg
)
242 return page_address(sg_page(sg
)) + sg
->offset
;
245 int sg_nents(struct scatterlist
*sg
);
246 int sg_nents_for_len(struct scatterlist
*sg
, u64 len
);
247 struct scatterlist
*sg_next(struct scatterlist
*);
248 struct scatterlist
*sg_last(struct scatterlist
*s
, unsigned int);
249 void sg_init_table(struct scatterlist
*, unsigned int);
250 void sg_init_one(struct scatterlist
*, const void *, unsigned int);
251 int sg_split(struct scatterlist
*in
, const int in_mapped_nents
,
252 const off_t skip
, const int nb_splits
,
253 const size_t *split_sizes
,
254 struct scatterlist
**out
, int *out_mapped_nents
,
257 typedef struct scatterlist
*(sg_alloc_fn
)(unsigned int, gfp_t
);
258 typedef void (sg_free_fn
)(struct scatterlist
*, unsigned int);
260 void __sg_free_table(struct sg_table
*, unsigned int, bool, sg_free_fn
*);
261 void sg_free_table(struct sg_table
*);
262 int __sg_alloc_table(struct sg_table
*, unsigned int, unsigned int,
263 struct scatterlist
*, gfp_t
, sg_alloc_fn
*);
264 int sg_alloc_table(struct sg_table
*, unsigned int, gfp_t
);
265 int sg_alloc_table_from_pages(struct sg_table
*sgt
,
266 struct page
**pages
, unsigned int n_pages
,
267 unsigned long offset
, unsigned long size
,
270 size_t sg_copy_buffer(struct scatterlist
*sgl
, unsigned int nents
, void *buf
,
271 size_t buflen
, off_t skip
, bool to_buffer
);
273 size_t sg_copy_from_buffer(struct scatterlist
*sgl
, unsigned int nents
,
274 const void *buf
, size_t buflen
);
275 size_t sg_copy_to_buffer(struct scatterlist
*sgl
, unsigned int nents
,
276 void *buf
, size_t buflen
);
278 size_t sg_pcopy_from_buffer(struct scatterlist
*sgl
, unsigned int nents
,
279 const void *buf
, size_t buflen
, off_t skip
);
280 size_t sg_pcopy_to_buffer(struct scatterlist
*sgl
, unsigned int nents
,
281 void *buf
, size_t buflen
, off_t skip
);
282 size_t sg_zero_buffer(struct scatterlist
*sgl
, unsigned int nents
,
283 size_t buflen
, off_t skip
);
286 * Maximum number of entries that will be allocated in one piece, if
287 * a list larger than this is required then chaining will be utilized.
289 #define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
292 * The maximum number of SG segments that we will put inside a
293 * scatterlist (unless chaining is used). Should ideally fit inside a
294 * single page, to avoid a higher order allocation. We could define this
295 * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order. The
296 * minimum value is 32
298 #define SG_CHUNK_SIZE 128
301 * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
302 * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
304 #ifdef CONFIG_ARCH_HAS_SG_CHAIN
305 #define SG_MAX_SEGMENTS 2048
307 #define SG_MAX_SEGMENTS SG_CHUNK_SIZE
310 #ifdef CONFIG_SG_POOL
311 void sg_free_table_chained(struct sg_table
*table
, bool first_chunk
);
312 int sg_alloc_table_chained(struct sg_table
*table
, int nents
,
313 struct scatterlist
*first_chunk
);
319 * Iterates over sg entries page-by-page. On each successful iteration,
320 * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
321 * to get the current page and its dma address. @piter->sg will point to the
322 * sg holding this page and @piter->sg_pgoffset to the page's page offset
323 * within the sg. The iteration will stop either when a maximum number of sg
324 * entries was reached or a terminating sg (sg_last(sg) == true) was reached.
326 struct sg_page_iter
{
327 struct scatterlist
*sg
; /* sg holding the page */
328 unsigned int sg_pgoffset
; /* page offset within the sg */
330 /* these are internal states, keep away */
331 unsigned int __nents
; /* remaining sg entries */
332 int __pg_advance
; /* nr pages to advance at the
336 bool __sg_page_iter_next(struct sg_page_iter
*piter
);
337 void __sg_page_iter_start(struct sg_page_iter
*piter
,
338 struct scatterlist
*sglist
, unsigned int nents
,
339 unsigned long pgoffset
);
341 * sg_page_iter_page - get the current page held by the page iterator
342 * @piter: page iterator holding the page
344 static inline struct page
*sg_page_iter_page(struct sg_page_iter
*piter
)
346 return nth_page(sg_page(piter
->sg
), piter
->sg_pgoffset
);
350 * sg_page_iter_dma_address - get the dma address of the current page held by
352 * @piter: page iterator holding the page
354 static inline dma_addr_t
sg_page_iter_dma_address(struct sg_page_iter
*piter
)
356 return sg_dma_address(piter
->sg
) + (piter
->sg_pgoffset
<< PAGE_SHIFT
);
360 * for_each_sg_page - iterate over the pages of the given sg list
361 * @sglist: sglist to iterate over
362 * @piter: page iterator to hold current page, sg, sg_pgoffset
363 * @nents: maximum number of sg entries to iterate over
364 * @pgoffset: starting page offset
366 #define for_each_sg_page(sglist, piter, nents, pgoffset) \
367 for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
368 __sg_page_iter_next(piter);)
371 * Mapping sg iterator
373 * Iterates over sg entries mapping page-by-page. On each successful
374 * iteration, @miter->page points to the mapped page and
375 * @miter->length bytes of data can be accessed at @miter->addr. As
376 * long as an interation is enclosed between start and stop, the user
377 * is free to choose control structure and when to stop.
379 * @miter->consumed is set to @miter->length on each iteration. It
380 * can be adjusted if the user can't consume all the bytes in one go.
381 * Also, a stopped iteration can be resumed by calling next on it.
382 * This is useful when iteration needs to release all resources and
383 * continue later (e.g. at the next interrupt).
386 #define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */
387 #define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */
388 #define SG_MITER_FROM_SG (1 << 2) /* nop */
390 struct sg_mapping_iter
{
391 /* the following three fields can be accessed directly */
392 struct page
*page
; /* currently mapped page */
393 void *addr
; /* pointer to the mapped area */
394 size_t length
; /* length of the mapped area */
395 size_t consumed
; /* number of consumed bytes */
396 struct sg_page_iter piter
; /* page iterator */
398 /* these are internal states, keep away */
399 unsigned int __offset
; /* offset within page */
400 unsigned int __remaining
; /* remaining bytes on page */
401 unsigned int __flags
;
404 void sg_miter_start(struct sg_mapping_iter
*miter
, struct scatterlist
*sgl
,
405 unsigned int nents
, unsigned int flags
);
406 bool sg_miter_skip(struct sg_mapping_iter
*miter
, off_t offset
);
407 bool sg_miter_next(struct sg_mapping_iter
*miter
);
408 void sg_miter_stop(struct sg_mapping_iter
*miter
);
410 #endif /* _LINUX_SCATTERLIST_H */