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 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 struct scatterlist
*sg_next(struct scatterlist
*);
225 struct scatterlist
*sg_last(struct scatterlist
*s
, unsigned int);
226 void sg_init_table(struct scatterlist
*, unsigned int);
227 void sg_init_one(struct scatterlist
*, const void *, unsigned int);
229 typedef struct scatterlist
*(sg_alloc_fn
)(unsigned int, gfp_t
);
230 typedef void (sg_free_fn
)(struct scatterlist
*, unsigned int);
232 void __sg_free_table(struct sg_table
*, unsigned int, sg_free_fn
*);
233 void sg_free_table(struct sg_table
*);
234 int __sg_alloc_table(struct sg_table
*, unsigned int, unsigned int, gfp_t
,
236 int sg_alloc_table(struct sg_table
*, unsigned int, gfp_t
);
237 int sg_alloc_table_from_pages(struct sg_table
*sgt
,
238 struct page
**pages
, unsigned int n_pages
,
239 unsigned long offset
, unsigned long size
,
242 size_t sg_copy_from_buffer(struct scatterlist
*sgl
, unsigned int nents
,
243 void *buf
, size_t buflen
);
244 size_t sg_copy_to_buffer(struct scatterlist
*sgl
, unsigned int nents
,
245 void *buf
, size_t buflen
);
248 * Maximum number of entries that will be allocated in one piece, if
249 * a list larger than this is required then chaining will be utilized.
251 #define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
256 * Iterates over sg entries page-by-page. On each successful iteration,
257 * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
258 * to get the current page and its dma address. @piter->sg will point to the
259 * sg holding this page and @piter->sg_pgoffset to the page's page offset
260 * within the sg. The iteration will stop either when a maximum number of sg
261 * entries was reached or a terminating sg (sg_last(sg) == true) was reached.
263 struct sg_page_iter
{
264 struct scatterlist
*sg
; /* sg holding the page */
265 unsigned int sg_pgoffset
; /* page offset within the sg */
267 /* these are internal states, keep away */
268 unsigned int __nents
; /* remaining sg entries */
269 int __pg_advance
; /* nr pages to advance at the
273 bool __sg_page_iter_next(struct sg_page_iter
*piter
);
274 void __sg_page_iter_start(struct sg_page_iter
*piter
,
275 struct scatterlist
*sglist
, unsigned int nents
,
276 unsigned long pgoffset
);
278 * sg_page_iter_page - get the current page held by the page iterator
279 * @piter: page iterator holding the page
281 static inline struct page
*sg_page_iter_page(struct sg_page_iter
*piter
)
283 return nth_page(sg_page(piter
->sg
), piter
->sg_pgoffset
);
287 * sg_page_iter_dma_address - get the dma address of the current page held by
289 * @piter: page iterator holding the page
291 static inline dma_addr_t
sg_page_iter_dma_address(struct sg_page_iter
*piter
)
293 return sg_dma_address(piter
->sg
) + (piter
->sg_pgoffset
<< PAGE_SHIFT
);
297 * for_each_sg_page - iterate over the pages of the given sg list
298 * @sglist: sglist to iterate over
299 * @piter: page iterator to hold current page, sg, sg_pgoffset
300 * @nents: maximum number of sg entries to iterate over
301 * @pgoffset: starting page offset
303 #define for_each_sg_page(sglist, piter, nents, pgoffset) \
304 for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
305 __sg_page_iter_next(piter);)
308 * Mapping sg iterator
310 * Iterates over sg entries mapping page-by-page. On each successful
311 * iteration, @miter->page points to the mapped page and
312 * @miter->length bytes of data can be accessed at @miter->addr. As
313 * long as an interation is enclosed between start and stop, the user
314 * is free to choose control structure and when to stop.
316 * @miter->consumed is set to @miter->length on each iteration. It
317 * can be adjusted if the user can't consume all the bytes in one go.
318 * Also, a stopped iteration can be resumed by calling next on it.
319 * This is useful when iteration needs to release all resources and
320 * continue later (e.g. at the next interrupt).
323 #define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */
324 #define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */
325 #define SG_MITER_FROM_SG (1 << 2) /* nop */
327 struct sg_mapping_iter
{
328 /* the following three fields can be accessed directly */
329 struct page
*page
; /* currently mapped page */
330 void *addr
; /* pointer to the mapped area */
331 size_t length
; /* length of the mapped area */
332 size_t consumed
; /* number of consumed bytes */
333 struct sg_page_iter piter
; /* page iterator */
335 /* these are internal states, keep away */
336 unsigned int __offset
; /* offset within page */
337 unsigned int __remaining
; /* remaining bytes on page */
338 unsigned int __flags
;
341 void sg_miter_start(struct sg_mapping_iter
*miter
, struct scatterlist
*sgl
,
342 unsigned int nents
, unsigned int flags
);
343 bool sg_miter_next(struct sg_mapping_iter
*miter
);
344 void sg_miter_stop(struct sg_mapping_iter
*miter
);
346 #endif /* _LINUX_SCATTERLIST_H */
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