1 #ifndef _LINUX_SCATTERLIST_H
2 #define _LINUX_SCATTERLIST_H
4 #include <linux/string.h>
9 #include <asm/scatterlist.h>
13 struct scatterlist *sgl; /* the list */
14 unsigned int nents; /* number of mapped entries */
15 unsigned int orig_nents; /* original size of list */
19 * Notes on SG table design.
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.
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.
29 * If bit 1 is set, then this sg entry is the last element in a list.
35 #define SG_MAGIC 0x87654321
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 :-)
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))
48 * sg_assign_page - Assign a given page to an SG entry
53 * Assign page to sg entry. Also see sg_set_page(), the most commonly used
57 static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
59 unsigned long page_link = sg->page_link & 0x3;
62 * In order for the low bit stealing approach to work, pages
63 * must be aligned at a 32-bit boundary as a minimum.
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));
70 sg->page_link = page_link | (unsigned long) page;
74 * sg_set_page - Set sg entry to point at given page
77 * @len: Length of data
78 * @offset: Offset into page
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
87 static inline void sg_set_page(struct scatterlist *sg, struct page *page,
88 unsigned int len, unsigned int offset)
90 sg_assign_page(sg, page);
95 static inline struct page *sg_page(struct scatterlist *sg)
97 #ifdef CONFIG_DEBUG_SG
98 BUG_ON(sg->sg_magic != SG_MAGIC);
99 BUG_ON(sg_is_chain(sg));
101 return (struct page *)((sg)->page_link & ~0x3);
105 * sg_set_buf - Set sg entry to point at given data
108 * @buflen: Data length
111 static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
114 #ifdef CONFIG_DEBUG_SG
115 BUG_ON(!virt_addr_valid(buf));
117 sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
121 * Loop over each sg element, following the pointer to a new list if necessary
123 #define for_each_sg(sglist, sg, nr, __i) \
124 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
127 * sg_chain - Chain two sglists together
128 * @prv: First scatterlist
129 * @prv_nents: Number of entries in prv
130 * @sgl: Second scatterlist
133 * Links @prv@ and @sgl@ together, to form a longer scatterlist.
136 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
137 struct scatterlist *sgl)
139 #ifndef CONFIG_ARCH_HAS_SG_CHAIN
144 * offset and length are unused for chain entry. Clear them.
146 prv[prv_nents - 1].offset = 0;
147 prv[prv_nents - 1].length = 0;
150 * Set lowest bit to indicate a link pointer, and make sure to clear
151 * the termination bit if it happens to be set.
153 prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
157 * sg_mark_end - Mark the end of the scatterlist
158 * @sg: SG entryScatterlist
161 * Marks the passed in sg entry as the termination point for the sg
162 * table. A call to sg_next() on this entry will return NULL.
165 static inline void sg_mark_end(struct scatterlist *sg)
167 #ifdef CONFIG_DEBUG_SG
168 BUG_ON(sg->sg_magic != SG_MAGIC);
171 * Set termination bit, clear potential chain bit
173 sg->page_link |= 0x02;
174 sg->page_link &= ~0x01;
178 * sg_unmark_end - Undo setting the end of the scatterlist
179 * @sg: SG entryScatterlist
182 * Removes the termination marker from the given entry of the scatterlist.
185 static inline void sg_unmark_end(struct scatterlist *sg)
187 #ifdef CONFIG_DEBUG_SG
188 BUG_ON(sg->sg_magic != SG_MAGIC);
190 sg->page_link &= ~0x02;
194 * sg_phys - Return physical address of an sg entry
198 * This calls page_to_phys() on the page in this sg entry, and adds the
199 * sg offset. The caller must know that it is legal to call page_to_phys()
203 static inline dma_addr_t sg_phys(struct scatterlist *sg)
205 return page_to_phys(sg_page(sg)) + sg->offset;
209 * sg_virt - Return virtual address of an sg entry
213 * This calls page_address() on the page in this sg entry, and adds the
214 * sg offset. The caller must know that the sg page has a valid virtual
218 static inline void *sg_virt(struct scatterlist *sg)
220 return page_address(sg_page(sg)) + sg->offset;
223 int sg_nents(struct scatterlist *sg);
224 int sg_nents_for_len(struct scatterlist *sg, u64 len);
225 struct scatterlist *sg_next(struct scatterlist *);
226 struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
227 void sg_init_table(struct scatterlist *, unsigned int);
228 void sg_init_one(struct scatterlist *, const void *, unsigned int);
230 typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
231 typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
233 void __sg_free_table(struct sg_table *, unsigned int, bool, sg_free_fn *);
234 void sg_free_table(struct sg_table *);
235 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
236 struct scatterlist *, gfp_t, sg_alloc_fn *);
237 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
238 int sg_alloc_table_from_pages(struct sg_table *sgt,
239 struct page **pages, unsigned int n_pages,
240 unsigned long offset, unsigned long size,
243 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
244 void *buf, size_t buflen);
245 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
246 void *buf, size_t buflen);
248 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
249 void *buf, size_t buflen, off_t skip);
250 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
251 void *buf, size_t buflen, off_t skip);
254 * Maximum number of entries that will be allocated in one piece, if
255 * a list larger than this is required then chaining will be utilized.
257 #define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
262 * Iterates over sg entries page-by-page. On each successful iteration,
263 * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
264 * to get the current page and its dma address. @piter->sg will point to the
265 * sg holding this page and @piter->sg_pgoffset to the page's page offset
266 * within the sg. The iteration will stop either when a maximum number of sg
267 * entries was reached or a terminating sg (sg_last(sg) == true) was reached.
269 struct sg_page_iter {
270 struct scatterlist *sg; /* sg holding the page */
271 unsigned int sg_pgoffset; /* page offset within the sg */
273 /* these are internal states, keep away */
274 unsigned int __nents; /* remaining sg entries */
275 int __pg_advance; /* nr pages to advance at the
279 bool __sg_page_iter_next(struct sg_page_iter *piter);
280 void __sg_page_iter_start(struct sg_page_iter *piter,
281 struct scatterlist *sglist, unsigned int nents,
282 unsigned long pgoffset);
284 * sg_page_iter_page - get the current page held by the page iterator
285 * @piter: page iterator holding the page
287 static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
289 return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
293 * sg_page_iter_dma_address - get the dma address of the current page held by
295 * @piter: page iterator holding the page
297 static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter)
299 return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT);
303 * for_each_sg_page - iterate over the pages of the given sg list
304 * @sglist: sglist to iterate over
305 * @piter: page iterator to hold current page, sg, sg_pgoffset
306 * @nents: maximum number of sg entries to iterate over
307 * @pgoffset: starting page offset
309 #define for_each_sg_page(sglist, piter, nents, pgoffset) \
310 for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
311 __sg_page_iter_next(piter);)
314 * Mapping sg iterator
316 * Iterates over sg entries mapping page-by-page. On each successful
317 * iteration, @miter->page points to the mapped page and
318 * @miter->length bytes of data can be accessed at @miter->addr. As
319 * long as an interation is enclosed between start and stop, the user
320 * is free to choose control structure and when to stop.
322 * @miter->consumed is set to @miter->length on each iteration. It
323 * can be adjusted if the user can't consume all the bytes in one go.
324 * Also, a stopped iteration can be resumed by calling next on it.
325 * This is useful when iteration needs to release all resources and
326 * continue later (e.g. at the next interrupt).
329 #define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */
330 #define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */
331 #define SG_MITER_FROM_SG (1 << 2) /* nop */
333 struct sg_mapping_iter {
334 /* the following three fields can be accessed directly */
335 struct page *page; /* currently mapped page */
336 void *addr; /* pointer to the mapped area */
337 size_t length; /* length of the mapped area */
338 size_t consumed; /* number of consumed bytes */
339 struct sg_page_iter piter; /* page iterator */
341 /* these are internal states, keep away */
342 unsigned int __offset; /* offset within page */
343 unsigned int __remaining; /* remaining bytes on page */
344 unsigned int __flags;
347 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
348 unsigned int nents, unsigned int flags);
349 bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
350 bool sg_miter_next(struct sg_mapping_iter *miter);
351 void sg_miter_stop(struct sg_mapping_iter *miter);
353 #endif /* _LINUX_SCATTERLIST_H */