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 sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
118 * Loop over each sg element, following the pointer to a new list if necessary
120 #define for_each_sg(sglist, sg, nr, __i) \
121 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
124 * sg_chain - Chain two sglists together
125 * @prv: First scatterlist
126 * @prv_nents: Number of entries in prv
127 * @sgl: Second scatterlist
130 * Links @prv@ and @sgl@ together, to form a longer scatterlist.
133 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
134 struct scatterlist *sgl)
136 #ifndef ARCH_HAS_SG_CHAIN
141 * offset and length are unused for chain entry. Clear them.
143 prv[prv_nents - 1].offset = 0;
144 prv[prv_nents - 1].length = 0;
147 * Set lowest bit to indicate a link pointer, and make sure to clear
148 * the termination bit if it happens to be set.
150 prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
154 * sg_mark_end - Mark the end of the scatterlist
155 * @sg: SG entryScatterlist
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.
162 static inline void sg_mark_end(struct scatterlist *sg)
164 #ifdef CONFIG_DEBUG_SG
165 BUG_ON(sg->sg_magic != SG_MAGIC);
168 * Set termination bit, clear potential chain bit
170 sg->page_link |= 0x02;
171 sg->page_link &= ~0x01;
175 * sg_phys - Return physical address of an sg entry
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()
184 static inline dma_addr_t sg_phys(struct scatterlist *sg)
186 return page_to_phys(sg_page(sg)) + sg->offset;
190 * sg_virt - Return virtual address of an sg entry
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
199 static inline void *sg_virt(struct scatterlist *sg)
201 return page_address(sg_page(sg)) + sg->offset;
204 int sg_nents(struct scatterlist *sg);
205 struct scatterlist *sg_next(struct scatterlist *);
206 struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
207 void sg_init_table(struct scatterlist *, unsigned int);
208 void sg_init_one(struct scatterlist *, const void *, unsigned int);
210 typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
211 typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
213 void __sg_free_table(struct sg_table *, unsigned int, sg_free_fn *);
214 void sg_free_table(struct sg_table *);
215 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, gfp_t,
217 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
218 int sg_alloc_table_from_pages(struct sg_table *sgt,
219 struct page **pages, unsigned int n_pages,
220 unsigned long offset, unsigned long size,
223 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
224 void *buf, size_t buflen);
225 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
226 void *buf, size_t buflen);
229 * Maximum number of entries that will be allocated in one piece, if
230 * a list larger than this is required then chaining will be utilized.
232 #define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
237 * Iterates over sg entries page-by-page. On each successful iteration,
238 * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
239 * to get the current page and its dma address. @piter->sg will point to the
240 * sg holding this page and @piter->sg_pgoffset to the page's page offset
241 * within the sg. The iteration will stop either when a maximum number of sg
242 * entries was reached or a terminating sg (sg_last(sg) == true) was reached.
244 struct sg_page_iter {
245 struct scatterlist *sg; /* sg holding the page */
246 unsigned int sg_pgoffset; /* page offset within the sg */
248 /* these are internal states, keep away */
249 unsigned int __nents; /* remaining sg entries */
250 int __pg_advance; /* nr pages to advance at the
254 bool __sg_page_iter_next(struct sg_page_iter *piter);
255 void __sg_page_iter_start(struct sg_page_iter *piter,
256 struct scatterlist *sglist, unsigned int nents,
257 unsigned long pgoffset);
259 * sg_page_iter_page - get the current page held by the page iterator
260 * @piter: page iterator holding the page
262 static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
264 return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
268 * sg_page_iter_dma_address - get the dma address of the current page held by
270 * @piter: page iterator holding the page
272 static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter)
274 return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT);
278 * for_each_sg_page - iterate over the pages of the given sg list
279 * @sglist: sglist to iterate over
280 * @piter: page iterator to hold current page, sg, sg_pgoffset
281 * @nents: maximum number of sg entries to iterate over
282 * @pgoffset: starting page offset
284 #define for_each_sg_page(sglist, piter, nents, pgoffset) \
285 for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
286 __sg_page_iter_next(piter);)
289 * Mapping sg iterator
291 * Iterates over sg entries mapping page-by-page. On each successful
292 * iteration, @miter->page points to the mapped page and
293 * @miter->length bytes of data can be accessed at @miter->addr. As
294 * long as an interation is enclosed between start and stop, the user
295 * is free to choose control structure and when to stop.
297 * @miter->consumed is set to @miter->length on each iteration. It
298 * can be adjusted if the user can't consume all the bytes in one go.
299 * Also, a stopped iteration can be resumed by calling next on it.
300 * This is useful when iteration needs to release all resources and
301 * continue later (e.g. at the next interrupt).
304 #define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */
305 #define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */
306 #define SG_MITER_FROM_SG (1 << 2) /* nop */
308 struct sg_mapping_iter {
309 /* the following three fields can be accessed directly */
310 struct page *page; /* currently mapped page */
311 void *addr; /* pointer to the mapped area */
312 size_t length; /* length of the mapped area */
313 size_t consumed; /* number of consumed bytes */
314 struct sg_page_iter piter; /* page iterator */
316 /* these are internal states, keep away */
317 unsigned int __offset; /* offset within page */
318 unsigned int __remaining; /* remaining bytes on page */
319 unsigned int __flags;
322 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
323 unsigned int nents, unsigned int flags);
324 bool sg_miter_next(struct sg_mapping_iter *miter);
325 void sg_miter_stop(struct sg_mapping_iter *miter);
327 #endif /* _LINUX_SCATTERLIST_H */