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1da177e4 LT |
1 | #ifndef _LINUX_SCATTERLIST_H |
2 | #define _LINUX_SCATTERLIST_H | |
3 | ||
d32311fe HX |
4 | #include <asm/scatterlist.h> |
5 | #include <linux/mm.h> | |
6 | #include <linux/string.h> | |
18dabf47 JA |
7 | #include <asm/io.h> |
8 | ||
9 | /* | |
10 | * Notes on SG table design. | |
11 | * | |
12 | * Architectures must provide an unsigned long page_link field in the | |
13 | * scatterlist struct. We use that to place the page pointer AND encode | |
14 | * information about the sg table as well. The two lower bits are reserved | |
15 | * for this information. | |
16 | * | |
17 | * If bit 0 is set, then the page_link contains a pointer to the next sg | |
18 | * table list. Otherwise the next entry is at sg + 1. | |
19 | * | |
20 | * If bit 1 is set, then this sg entry is the last element in a list. | |
21 | * | |
22 | * See sg_next(). | |
23 | * | |
24 | */ | |
1da177e4 | 25 | |
d6ec0842 JA |
26 | #define SG_MAGIC 0x87654321 |
27 | ||
82f66fbe JA |
28 | /** |
29 | * sg_set_page - Set sg entry to point at given page | |
30 | * @sg: SG entry | |
31 | * @page: The page | |
32 | * | |
33 | * Description: | |
34 | * Use this function to set an sg entry pointing at a page, never assign | |
35 | * the page directly. We encode sg table information in the lower bits | |
36 | * of the page pointer. See sg_page() for looking up the page belonging | |
37 | * to an sg entry. | |
38 | * | |
39 | **/ | |
40 | static inline void sg_set_page(struct scatterlist *sg, struct page *page) | |
41 | { | |
18dabf47 JA |
42 | unsigned long page_link = sg->page_link & 0x3; |
43 | ||
de26103d JA |
44 | /* |
45 | * In order for the low bit stealing approach to work, pages | |
46 | * must be aligned at a 32-bit boundary as a minimum. | |
47 | */ | |
48 | BUG_ON((unsigned long) page & 0x03); | |
d6ec0842 JA |
49 | #ifdef CONFIG_DEBUG_SG |
50 | BUG_ON(sg->sg_magic != SG_MAGIC); | |
51 | #endif | |
18dabf47 | 52 | sg->page_link = page_link | (unsigned long) page; |
82f66fbe JA |
53 | } |
54 | ||
18dabf47 | 55 | #define sg_page(sg) ((struct page *) ((sg)->page_link & ~0x3)) |
82f66fbe | 56 | |
18dabf47 JA |
57 | /** |
58 | * sg_set_buf - Set sg entry to point at given data | |
59 | * @sg: SG entry | |
60 | * @buf: Data | |
61 | * @buflen: Data length | |
62 | * | |
63 | **/ | |
03fd9cee | 64 | static inline void sg_set_buf(struct scatterlist *sg, const void *buf, |
d32311fe HX |
65 | unsigned int buflen) |
66 | { | |
82f66fbe | 67 | sg_set_page(sg, virt_to_page(buf)); |
1da177e4 LT |
68 | sg->offset = offset_in_page(buf); |
69 | sg->length = buflen; | |
70 | } | |
71 | ||
70eb8040 JA |
72 | /* |
73 | * We overload the LSB of the page pointer to indicate whether it's | |
74 | * a valid sg entry, or whether it points to the start of a new scatterlist. | |
75 | * Those low bits are there for everyone! (thanks mason :-) | |
76 | */ | |
18dabf47 JA |
77 | #define sg_is_chain(sg) ((sg)->page_link & 0x01) |
78 | #define sg_is_last(sg) ((sg)->page_link & 0x02) | |
70eb8040 | 79 | #define sg_chain_ptr(sg) \ |
18dabf47 | 80 | ((struct scatterlist *) ((sg)->page_link & ~0x03)) |
70eb8040 JA |
81 | |
82 | /** | |
83 | * sg_next - return the next scatterlist entry in a list | |
84 | * @sg: The current sg entry | |
85 | * | |
18dabf47 JA |
86 | * Description: |
87 | * Usually the next entry will be @sg@ + 1, but if this sg element is part | |
88 | * of a chained scatterlist, it could jump to the start of a new | |
89 | * scatterlist array. | |
70eb8040 | 90 | * |
18dabf47 | 91 | **/ |
70eb8040 JA |
92 | static inline struct scatterlist *sg_next(struct scatterlist *sg) |
93 | { | |
d6ec0842 JA |
94 | #ifdef CONFIG_DEBUG_SG |
95 | BUG_ON(sg->sg_magic != SG_MAGIC); | |
96 | #endif | |
18dabf47 JA |
97 | if (sg_is_last(sg)) |
98 | return NULL; | |
70eb8040 | 99 | |
18dabf47 | 100 | sg++; |
70eb8040 JA |
101 | if (unlikely(sg_is_chain(sg))) |
102 | sg = sg_chain_ptr(sg); | |
103 | ||
104 | return sg; | |
105 | } | |
96b418c9 JA |
106 | |
107 | /* | |
108 | * Loop over each sg element, following the pointer to a new list if necessary | |
109 | */ | |
110 | #define for_each_sg(sglist, sg, nr, __i) \ | |
111 | for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg)) | |
112 | ||
70eb8040 JA |
113 | /** |
114 | * sg_last - return the last scatterlist entry in a list | |
115 | * @sgl: First entry in the scatterlist | |
116 | * @nents: Number of entries in the scatterlist | |
117 | * | |
18dabf47 JA |
118 | * Description: |
119 | * Should only be used casually, it (currently) scan the entire list | |
120 | * to get the last entry. | |
70eb8040 | 121 | * |
18dabf47 JA |
122 | * Note that the @sgl@ pointer passed in need not be the first one, |
123 | * the important bit is that @nents@ denotes the number of entries that | |
124 | * exist from @sgl@. | |
70eb8040 | 125 | * |
18dabf47 | 126 | **/ |
70eb8040 JA |
127 | static inline struct scatterlist *sg_last(struct scatterlist *sgl, |
128 | unsigned int nents) | |
129 | { | |
130 | #ifndef ARCH_HAS_SG_CHAIN | |
131 | struct scatterlist *ret = &sgl[nents - 1]; | |
132 | #else | |
133 | struct scatterlist *sg, *ret = NULL; | |
134 | int i; | |
135 | ||
136 | for_each_sg(sgl, sg, nents, i) | |
137 | ret = sg; | |
138 | ||
d6ec0842 JA |
139 | #endif |
140 | #ifdef CONFIG_DEBUG_SG | |
141 | BUG_ON(sgl[0].sg_magic != SG_MAGIC); | |
142 | BUG_ON(!sg_is_last(ret)); | |
70eb8040 JA |
143 | #endif |
144 | return ret; | |
145 | } | |
146 | ||
147 | /** | |
148 | * sg_chain - Chain two sglists together | |
149 | * @prv: First scatterlist | |
150 | * @prv_nents: Number of entries in prv | |
151 | * @sgl: Second scatterlist | |
152 | * | |
18dabf47 JA |
153 | * Description: |
154 | * Links @prv@ and @sgl@ together, to form a longer scatterlist. | |
70eb8040 | 155 | * |
18dabf47 | 156 | **/ |
70eb8040 JA |
157 | static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, |
158 | struct scatterlist *sgl) | |
159 | { | |
160 | #ifndef ARCH_HAS_SG_CHAIN | |
161 | BUG(); | |
162 | #endif | |
18dabf47 | 163 | prv[prv_nents - 1].page_link = (unsigned long) sgl | 0x01; |
70eb8040 JA |
164 | } |
165 | ||
82f66fbe JA |
166 | /** |
167 | * sg_mark_end - Mark the end of the scatterlist | |
168 | * @sgl: Scatterlist | |
169 | * @nents: Number of entries in sgl | |
170 | * | |
171 | * Description: | |
172 | * Marks the last entry as the termination point for sg_next() | |
173 | * | |
174 | **/ | |
175 | static inline void sg_mark_end(struct scatterlist *sgl, unsigned int nents) | |
176 | { | |
18dabf47 | 177 | sgl[nents - 1].page_link = 0x02; |
82f66fbe JA |
178 | } |
179 | ||
180 | static inline void __sg_mark_end(struct scatterlist *sg) | |
181 | { | |
18dabf47 | 182 | sg->page_link |= 0x02; |
82f66fbe JA |
183 | } |
184 | ||
82f66fbe JA |
185 | /** |
186 | * sg_init_one - Initialize a single entry sg list | |
187 | * @sg: SG entry | |
188 | * @buf: Virtual address for IO | |
189 | * @buflen: IO length | |
190 | * | |
191 | * Notes: | |
192 | * This should not be used on a single entry that is part of a larger | |
193 | * table. Use sg_init_table() for that. | |
194 | * | |
195 | **/ | |
196 | static inline void sg_init_one(struct scatterlist *sg, const void *buf, | |
197 | unsigned int buflen) | |
198 | { | |
199 | memset(sg, 0, sizeof(*sg)); | |
d6ec0842 JA |
200 | #ifdef CONFIG_DEBUG_SG |
201 | sg->sg_magic = SG_MAGIC; | |
202 | #endif | |
82f66fbe JA |
203 | sg_mark_end(sg, 1); |
204 | sg_set_buf(sg, buf, buflen); | |
205 | } | |
206 | ||
207 | /** | |
208 | * sg_init_table - Initialize SG table | |
209 | * @sgl: The SG table | |
210 | * @nents: Number of entries in table | |
211 | * | |
212 | * Notes: | |
213 | * If this is part of a chained sg table, sg_mark_end() should be | |
214 | * used only on the last table part. | |
215 | * | |
216 | **/ | |
217 | static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents) | |
218 | { | |
219 | memset(sgl, 0, sizeof(*sgl) * nents); | |
220 | sg_mark_end(sgl, nents); | |
d6ec0842 JA |
221 | #ifdef CONFIG_DEBUG_SG |
222 | { | |
223 | int i; | |
224 | for (i = 0; i < nents; i++) | |
225 | sgl[i].sg_magic = SG_MAGIC; | |
226 | } | |
227 | #endif | |
82f66fbe JA |
228 | } |
229 | ||
230 | /** | |
231 | * sg_phys - Return physical address of an sg entry | |
232 | * @sg: SG entry | |
233 | * | |
234 | * Description: | |
235 | * This calls page_to_phys() on the page in this sg entry, and adds the | |
236 | * sg offset. The caller must know that it is legal to call page_to_phys() | |
237 | * on the sg page. | |
238 | * | |
239 | **/ | |
240 | static inline unsigned long sg_phys(struct scatterlist *sg) | |
241 | { | |
242 | return page_to_phys(sg_page(sg)) + sg->offset; | |
243 | } | |
244 | ||
245 | /** | |
246 | * sg_virt - Return virtual address of an sg entry | |
18dabf47 | 247 | * @sg: SG entry |
82f66fbe JA |
248 | * |
249 | * Description: | |
250 | * This calls page_address() on the page in this sg entry, and adds the | |
251 | * sg offset. The caller must know that the sg page has a valid virtual | |
252 | * mapping. | |
253 | * | |
254 | **/ | |
255 | static inline void *sg_virt(struct scatterlist *sg) | |
256 | { | |
257 | return page_address(sg_page(sg)) + sg->offset; | |
258 | } | |
259 | ||
1da177e4 | 260 | #endif /* _LINUX_SCATTERLIST_H */ |