1 #ifndef _LINUX_SCATTERLIST_H
2 #define _LINUX_SCATTERLIST_H
3
4 #include <linux/string.h>
5 #include <linux/bug.h>
6 #include <linux/mm.h>
7
8 #include <asm/types.h>
9 #include <asm/scatterlist.h>
10 #include <asm/io.h>
11
12 struct sg_table {
13 struct scatterlist *sgl; /* the list */
14 unsigned int nents; /* number of mapped entries */
15 unsigned int orig_nents; /* original size of list */
16 };
17
18 /*
19 * Notes on SG table design.
20 *
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.
25 *
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.
28 *
29 * If bit 1 is set, then this sg entry is the last element in a list.
30 *
31 * See sg_next().
32 *
33 */
34
35 #define SG_MAGIC 0x87654321
36
37 /*
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 :-)
41 */
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))
46
47 /**
48 * sg_assign_page - Assign a given page to an SG entry
49 * @sg: SG entry
50 * @page: The page
51 *
52 * Description:
53 * Assign page to sg entry. Also see sg_set_page(), the most commonly used
54 * variant.
55 *
56 **/
sg_assign_page(struct scatterlist * sg,struct page * page)57 static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
58 {
59 unsigned long page_link = sg->page_link & 0x3;
60
61 /*
62 * In order for the low bit stealing approach to work, pages
63 * must be aligned at a 32-bit boundary as a minimum.
64 */
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));
69 #endif
70 sg->page_link = page_link | (unsigned long) page;
71 }
72
73 /**
74 * sg_set_page - Set sg entry to point at given page
75 * @sg: SG entry
76 * @page: The page
77 * @len: Length of data
78 * @offset: Offset into page
79 *
80 * Description:
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
84 * to an sg entry.
85 *
86 **/
sg_set_page(struct scatterlist * sg,struct page * page,unsigned int len,unsigned int offset)87 static inline void sg_set_page(struct scatterlist *sg, struct page *page,
88 unsigned int len, unsigned int offset)
89 {
90 sg_assign_page(sg, page);
91 sg->offset = offset;
92 sg->length = len;
93 }
94
sg_page(struct scatterlist * sg)95 static inline struct page *sg_page(struct scatterlist *sg)
96 {
97 #ifdef CONFIG_DEBUG_SG
98 BUG_ON(sg->sg_magic != SG_MAGIC);
99 BUG_ON(sg_is_chain(sg));
100 #endif
101 return (struct page *)((sg)->page_link & ~0x3);
102 }
103
104 /**
105 * sg_set_buf - Set sg entry to point at given data
106 * @sg: SG entry
107 * @buf: Data
108 * @buflen: Data length
109 *
110 **/
sg_set_buf(struct scatterlist * sg,const void * buf,unsigned int buflen)111 static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
112 unsigned int buflen)
113 {
114 sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
115 }
116
117 /*
118 * Loop over each sg element, following the pointer to a new list if necessary
119 */
120 #define for_each_sg(sglist, sg, nr, __i) \
121 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
122
123 /**
124 * sg_chain - Chain two sglists together
125 * @prv: First scatterlist
126 * @prv_nents: Number of entries in prv
127 * @sgl: Second scatterlist
128 *
129 * Description:
130 * Links @prv@ and @sgl@ together, to form a longer scatterlist.
131 *
132 **/
sg_chain(struct scatterlist * prv,unsigned int prv_nents,struct scatterlist * sgl)133 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
134 struct scatterlist *sgl)
135 {
136 #ifndef ARCH_HAS_SG_CHAIN
137 BUG();
138 #endif
139
140 /*
141 * offset and length are unused for chain entry. Clear them.
142 */
143 prv[prv_nents - 1].offset = 0;
144 prv[prv_nents - 1].length = 0;
145
146 /*
147 * Set lowest bit to indicate a link pointer, and make sure to clear
148 * the termination bit if it happens to be set.
149 */
150 prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
151 }
152
153 /**
154 * sg_mark_end - Mark the end of the scatterlist
155 * @sg: SG entryScatterlist
156 *
157 * Description:
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.
160 *
161 **/
sg_mark_end(struct scatterlist * sg)162 static inline void sg_mark_end(struct scatterlist *sg)
163 {
164 #ifdef CONFIG_DEBUG_SG
165 BUG_ON(sg->sg_magic != SG_MAGIC);
166 #endif
167 /*
168 * Set termination bit, clear potential chain bit
169 */
170 sg->page_link |= 0x02;
171 sg->page_link &= ~0x01;
172 }
173
174 /**
175 * sg_phys - Return physical address of an sg entry
176 * @sg: SG entry
177 *
178 * Description:
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()
181 * on the sg page.
182 *
183 **/
sg_phys(struct scatterlist * sg)184 static inline dma_addr_t sg_phys(struct scatterlist *sg)
185 {
186 return page_to_phys(sg_page(sg)) + sg->offset;
187 }
188
189 /**
190 * sg_virt - Return virtual address of an sg entry
191 * @sg: SG entry
192 *
193 * Description:
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
196 * mapping.
197 *
198 **/
sg_virt(struct scatterlist * sg)199 static inline void *sg_virt(struct scatterlist *sg)
200 {
201 return page_address(sg_page(sg)) + sg->offset;
202 }
203
204 struct scatterlist *sg_next(struct scatterlist *);
205 struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
206 void sg_init_table(struct scatterlist *, unsigned int);
207 void sg_init_one(struct scatterlist *, const void *, unsigned int);
208
209 typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
210 typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
211
212 void __sg_free_table(struct sg_table *, unsigned int, sg_free_fn *);
213 void sg_free_table(struct sg_table *);
214 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, gfp_t,
215 sg_alloc_fn *);
216 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
217
218 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
219 void *buf, size_t buflen);
220 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
221 void *buf, size_t buflen);
222
223 /*
224 * Maximum number of entries that will be allocated in one piece, if
225 * a list larger than this is required then chaining will be utilized.
226 */
227 #define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
228
229
230 /*
231 * Mapping sg iterator
232 *
233 * Iterates over sg entries mapping page-by-page. On each successful
234 * iteration, @miter->page points to the mapped page and
235 * @miter->length bytes of data can be accessed at @miter->addr. As
236 * long as an interation is enclosed between start and stop, the user
237 * is free to choose control structure and when to stop.
238 *
239 * @miter->consumed is set to @miter->length on each iteration. It
240 * can be adjusted if the user can't consume all the bytes in one go.
241 * Also, a stopped iteration can be resumed by calling next on it.
242 * This is useful when iteration needs to release all resources and
243 * continue later (e.g. at the next interrupt).
244 */
245
246 #define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */
247 #define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */
248 #define SG_MITER_FROM_SG (1 << 2) /* nop */
249
250 struct sg_mapping_iter {
251 /* the following three fields can be accessed directly */
252 struct page *page; /* currently mapped page */
253 void *addr; /* pointer to the mapped area */
254 size_t length; /* length of the mapped area */
255 size_t consumed; /* number of consumed bytes */
256
257 /* these are internal states, keep away */
258 struct scatterlist *__sg; /* current entry */
259 unsigned int __nents; /* nr of remaining entries */
260 unsigned int __offset; /* offset within sg */
261 unsigned int __flags;
262 };
263
264 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
265 unsigned int nents, unsigned int flags);
266 bool sg_miter_next(struct sg_mapping_iter *miter);
267 void sg_miter_stop(struct sg_mapping_iter *miter);
268
269 #endif /* _LINUX_SCATTERLIST_H */
270