1 #ifndef _LINUX_SCATTERLIST_H
2 #define _LINUX_SCATTERLIST_H
5 #include <asm/scatterlist.h>
7 #include <linux/string.h>
11 struct scatterlist *sgl; /* the list */
12 unsigned int nents; /* number of mapped entries */
13 unsigned int orig_nents; /* original size of list */
17 * Notes on SG table design.
19 * Architectures must provide an unsigned long page_link field in the
20 * scatterlist struct. We use that to place the page pointer AND encode
21 * information about the sg table as well. The two lower bits are reserved
22 * for this information.
24 * If bit 0 is set, then the page_link contains a pointer to the next sg
25 * table list. Otherwise the next entry is at sg + 1.
27 * If bit 1 is set, then this sg entry is the last element in a list.
33 #define SG_MAGIC 0x87654321
36 * We overload the LSB of the page pointer to indicate whether it's
37 * a valid sg entry, or whether it points to the start of a new scatterlist.
38 * Those low bits are there for everyone! (thanks mason :-)
40 #define sg_is_chain(sg) ((sg)->page_link & 0x01)
41 #define sg_is_last(sg) ((sg)->page_link & 0x02)
42 #define sg_chain_ptr(sg) \
43 ((struct scatterlist *) ((sg)->page_link & ~0x03))
46 * sg_assign_page - Assign a given page to an SG entry
51 * Assign page to sg entry. Also see sg_set_page(), the most commonly used
55 static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
57 unsigned long page_link = sg->page_link & 0x3;
60 * In order for the low bit stealing approach to work, pages
61 * must be aligned at a 32-bit boundary as a minimum.
63 BUG_ON((unsigned long) page & 0x03);
64 #ifdef CONFIG_DEBUG_SG
65 BUG_ON(sg->sg_magic != SG_MAGIC);
66 BUG_ON(sg_is_chain(sg));
68 sg->page_link = page_link | (unsigned long) page;
72 * sg_set_page - Set sg entry to point at given page
75 * @len: Length of data
76 * @offset: Offset into page
79 * Use this function to set an sg entry pointing at a page, never assign
80 * the page directly. We encode sg table information in the lower bits
81 * of the page pointer. See sg_page() for looking up the page belonging
85 static inline void sg_set_page(struct scatterlist *sg, struct page *page,
86 unsigned int len, unsigned int offset)
88 sg_assign_page(sg, page);
93 static inline struct page *sg_page(struct scatterlist *sg)
95 #ifdef CONFIG_DEBUG_SG
96 BUG_ON(sg->sg_magic != SG_MAGIC);
97 BUG_ON(sg_is_chain(sg));
99 return (struct page *)((sg)->page_link & ~0x3);
103 * sg_set_buf - Set sg entry to point at given data
106 * @buflen: Data length
109 static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
112 sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
116 * Loop over each sg element, following the pointer to a new list if necessary
118 #define for_each_sg(sglist, sg, nr, __i) \
119 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
122 * sg_chain - Chain two sglists together
123 * @prv: First scatterlist
124 * @prv_nents: Number of entries in prv
125 * @sgl: Second scatterlist
128 * Links @prv@ and @sgl@ together, to form a longer scatterlist.
131 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
132 struct scatterlist *sgl)
134 #ifndef ARCH_HAS_SG_CHAIN
139 * offset and length are unused for chain entry. Clear them.
141 prv[prv_nents - 1].offset = 0;
142 prv[prv_nents - 1].length = 0;
145 * Set lowest bit to indicate a link pointer, and make sure to clear
146 * the termination bit if it happens to be set.
148 prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
152 * sg_mark_end - Mark the end of the scatterlist
153 * @sg: SG entryScatterlist
156 * Marks the passed in sg entry as the termination point for the sg
157 * table. A call to sg_next() on this entry will return NULL.
160 static inline void sg_mark_end(struct scatterlist *sg)
162 #ifdef CONFIG_DEBUG_SG
163 BUG_ON(sg->sg_magic != SG_MAGIC);
166 * Set termination bit, clear potential chain bit
168 sg->page_link |= 0x02;
169 sg->page_link &= ~0x01;
173 * sg_phys - Return physical address of an sg entry
177 * This calls page_to_phys() on the page in this sg entry, and adds the
178 * sg offset. The caller must know that it is legal to call page_to_phys()
182 static inline dma_addr_t sg_phys(struct scatterlist *sg)
184 return page_to_phys(sg_page(sg)) + sg->offset;
188 * sg_virt - Return virtual address of an sg entry
192 * This calls page_address() on the page in this sg entry, and adds the
193 * sg offset. The caller must know that the sg page has a valid virtual
197 static inline void *sg_virt(struct scatterlist *sg)
199 return page_address(sg_page(sg)) + sg->offset;
202 struct scatterlist *sg_next(struct scatterlist *);
203 struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
204 void sg_init_table(struct scatterlist *, unsigned int);
205 void sg_init_one(struct scatterlist *, const void *, unsigned int);
207 typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
208 typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
210 void __sg_free_table(struct sg_table *, unsigned int, sg_free_fn *);
211 void sg_free_table(struct sg_table *);
212 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, gfp_t,
214 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
216 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
217 void *buf, size_t buflen);
218 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
219 void *buf, size_t buflen);
222 * Maximum number of entries that will be allocated in one piece, if
223 * a list larger than this is required then chaining will be utilized.
225 #define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
229 * Mapping sg iterator
231 * Iterates over sg entries mapping page-by-page. On each successful
232 * iteration, @miter->page points to the mapped page and
233 * @miter->length bytes of data can be accessed at @miter->addr. As
234 * long as an interation is enclosed between start and stop, the user
235 * is free to choose control structure and when to stop.
237 * @miter->consumed is set to @miter->length on each iteration. It
238 * can be adjusted if the user can't consume all the bytes in one go.
239 * Also, a stopped iteration can be resumed by calling next on it.
240 * This is useful when iteration needs to release all resources and
241 * continue later (e.g. at the next interrupt).
244 #define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */
246 struct sg_mapping_iter {
247 /* the following three fields can be accessed directly */
248 struct page *page; /* currently mapped page */
249 void *addr; /* pointer to the mapped area */
250 size_t length; /* length of the mapped area */
251 size_t consumed; /* number of consumed bytes */
253 /* these are internal states, keep away */
254 struct scatterlist *__sg; /* current entry */
255 unsigned int __nents; /* nr of remaining entries */
256 unsigned int __offset; /* offset within sg */
257 unsigned int __flags;
260 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
261 unsigned int nents, unsigned int flags);
262 bool sg_miter_next(struct sg_mapping_iter *miter);
263 void sg_miter_stop(struct sg_mapping_iter *miter);
265 #endif /* _LINUX_SCATTERLIST_H */