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_unmark_end - Undo setting the end of the scatterlist
176 * @sg: SG entryScatterlist
179 * Removes the termination marker from the given entry of the scatterlist.
182 static inline void sg_unmark_end(struct scatterlist
*sg
)
184 #ifdef CONFIG_DEBUG_SG
185 BUG_ON(sg
->sg_magic
!= SG_MAGIC
);
187 sg
->page_link
&= ~0x02;
191 * sg_phys - Return physical address of an sg entry
195 * This calls page_to_phys() on the page in this sg entry, and adds the
196 * sg offset. The caller must know that it is legal to call page_to_phys()
200 static inline dma_addr_t
sg_phys(struct scatterlist
*sg
)
202 return page_to_phys(sg_page(sg
)) + sg
->offset
;
206 * sg_virt - Return virtual address of an sg entry
210 * This calls page_address() on the page in this sg entry, and adds the
211 * sg offset. The caller must know that the sg page has a valid virtual
215 static inline void *sg_virt(struct scatterlist
*sg
)
217 return page_address(sg_page(sg
)) + sg
->offset
;
220 int sg_nents(struct scatterlist
*sg
);
221 struct scatterlist
*sg_next(struct scatterlist
*);
222 struct scatterlist
*sg_last(struct scatterlist
*s
, unsigned int);
223 void sg_init_table(struct scatterlist
*, unsigned int);
224 void sg_init_one(struct scatterlist
*, const void *, unsigned int);
226 typedef struct scatterlist
*(sg_alloc_fn
)(unsigned int, gfp_t
);
227 typedef void (sg_free_fn
)(struct scatterlist
*, unsigned int);
229 void __sg_free_table(struct sg_table
*, unsigned int, sg_free_fn
*);
230 void sg_free_table(struct sg_table
*);
231 int __sg_alloc_table(struct sg_table
*, unsigned int, unsigned int, gfp_t
,
233 int sg_alloc_table(struct sg_table
*, unsigned int, gfp_t
);
234 int sg_alloc_table_from_pages(struct sg_table
*sgt
,
235 struct page
**pages
, unsigned int n_pages
,
236 unsigned long offset
, unsigned long size
,
239 size_t sg_copy_from_buffer(struct scatterlist
*sgl
, unsigned int nents
,
240 void *buf
, size_t buflen
);
241 size_t sg_copy_to_buffer(struct scatterlist
*sgl
, unsigned int nents
,
242 void *buf
, size_t buflen
);
245 * Maximum number of entries that will be allocated in one piece, if
246 * a list larger than this is required then chaining will be utilized.
248 #define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
253 * Iterates over sg entries page-by-page. On each successful iteration,
254 * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
255 * to get the current page and its dma address. @piter->sg will point to the
256 * sg holding this page and @piter->sg_pgoffset to the page's page offset
257 * within the sg. The iteration will stop either when a maximum number of sg
258 * entries was reached or a terminating sg (sg_last(sg) == true) was reached.
260 struct sg_page_iter
{
261 struct scatterlist
*sg
; /* sg holding the page */
262 unsigned int sg_pgoffset
; /* page offset within the sg */
264 /* these are internal states, keep away */
265 unsigned int __nents
; /* remaining sg entries */
266 int __pg_advance
; /* nr pages to advance at the
270 bool __sg_page_iter_next(struct sg_page_iter
*piter
);
271 void __sg_page_iter_start(struct sg_page_iter
*piter
,
272 struct scatterlist
*sglist
, unsigned int nents
,
273 unsigned long pgoffset
);
275 * sg_page_iter_page - get the current page held by the page iterator
276 * @piter: page iterator holding the page
278 static inline struct page
*sg_page_iter_page(struct sg_page_iter
*piter
)
280 return nth_page(sg_page(piter
->sg
), piter
->sg_pgoffset
);
284 * sg_page_iter_dma_address - get the dma address of the current page held by
286 * @piter: page iterator holding the page
288 static inline dma_addr_t
sg_page_iter_dma_address(struct sg_page_iter
*piter
)
290 return sg_dma_address(piter
->sg
) + (piter
->sg_pgoffset
<< PAGE_SHIFT
);
294 * for_each_sg_page - iterate over the pages of the given sg list
295 * @sglist: sglist to iterate over
296 * @piter: page iterator to hold current page, sg, sg_pgoffset
297 * @nents: maximum number of sg entries to iterate over
298 * @pgoffset: starting page offset
300 #define for_each_sg_page(sglist, piter, nents, pgoffset) \
301 for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
302 __sg_page_iter_next(piter);)
305 * Mapping sg iterator
307 * Iterates over sg entries mapping page-by-page. On each successful
308 * iteration, @miter->page points to the mapped page and
309 * @miter->length bytes of data can be accessed at @miter->addr. As
310 * long as an interation is enclosed between start and stop, the user
311 * is free to choose control structure and when to stop.
313 * @miter->consumed is set to @miter->length on each iteration. It
314 * can be adjusted if the user can't consume all the bytes in one go.
315 * Also, a stopped iteration can be resumed by calling next on it.
316 * This is useful when iteration needs to release all resources and
317 * continue later (e.g. at the next interrupt).
320 #define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */
321 #define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */
322 #define SG_MITER_FROM_SG (1 << 2) /* nop */
324 struct sg_mapping_iter
{
325 /* the following three fields can be accessed directly */
326 struct page
*page
; /* currently mapped page */
327 void *addr
; /* pointer to the mapped area */
328 size_t length
; /* length of the mapped area */
329 size_t consumed
; /* number of consumed bytes */
330 struct sg_page_iter piter
; /* page iterator */
332 /* these are internal states, keep away */
333 unsigned int __offset
; /* offset within page */
334 unsigned int __remaining
; /* remaining bytes on page */
335 unsigned int __flags
;
338 void sg_miter_start(struct sg_mapping_iter
*miter
, struct scatterlist
*sgl
,
339 unsigned int nents
, unsigned int flags
);
340 bool sg_miter_next(struct sg_mapping_iter
*miter
);
341 void sg_miter_stop(struct sg_mapping_iter
*miter
);
343 #endif /* _LINUX_SCATTERLIST_H */
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