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1 | #ifndef _LINUX_SCATTERLIST_H |
2 | #define _LINUX_SCATTERLIST_H |
3 | |
4 | #include <asm/types.h> |
5 | #include <asm/scatterlist.h> |
6 | #include <linux/mm.h> |
7 | #include <linux/string.h> |
8 | #include <asm/io.h> |
9 | |
10 | struct sg_table { |
11 | struct scatterlist *sgl; /* the list */ |
12 | unsigned int nents; /* number of mapped entries */ |
13 | unsigned int orig_nents; /* original size of list */ |
14 | }; |
15 | |
16 | /* |
17 | * Notes on SG table design. |
18 | * |
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. |
23 | * |
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. |
26 | * |
27 | * If bit 1 is set, then this sg entry is the last element in a list. |
28 | * |
29 | * See sg_next(). |
30 | * |
31 | */ |
32 | |
33 | #define SG_MAGIC 0x87654321 |
34 | |
35 | /* |
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 :-) |
39 | */ |
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)) |
44 | |
45 | /** |
46 | * sg_assign_page - Assign a given page to an SG entry |
47 | * @sg: SG entry |
48 | * @page: The page |
49 | * |
50 | * Description: |
51 | * Assign page to sg entry. Also see sg_set_page(), the most commonly used |
52 | * variant. |
53 | * |
54 | **/ |
55 | static inline void sg_assign_page(struct scatterlist *sg, struct page *page) |
56 | { |
57 | unsigned long page_link = sg->page_link & 0x3; |
58 | |
59 | /* |
60 | * In order for the low bit stealing approach to work, pages |
61 | * must be aligned at a 32-bit boundary as a minimum. |
62 | */ |
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)); |
67 | #endif |
68 | sg->page_link = page_link | (unsigned long) page; |
69 | } |
70 | |
71 | /** |
72 | * sg_set_page - Set sg entry to point at given page |
73 | * @sg: SG entry |
74 | * @page: The page |
75 | * @len: Length of data |
76 | * @offset: Offset into page |
77 | * |
78 | * Description: |
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 |
82 | * to an sg entry. |
83 | * |
84 | **/ |
85 | static inline void sg_set_page(struct scatterlist *sg, struct page *page, |
86 | unsigned int len, unsigned int offset) |
87 | { |
88 | sg_assign_page(sg, page); |
89 | sg->offset = offset; |
90 | sg->length = len; |
91 | } |
92 | |
93 | static inline struct page *sg_page(struct scatterlist *sg) |
94 | { |
95 | #ifdef CONFIG_DEBUG_SG |
96 | BUG_ON(sg->sg_magic != SG_MAGIC); |
97 | BUG_ON(sg_is_chain(sg)); |
98 | #endif |
99 | return (struct page *)((sg)->page_link & ~0x3); |
100 | } |
101 | |
102 | /** |
103 | * sg_set_buf - Set sg entry to point at given data |
104 | * @sg: SG entry |
105 | * @buf: Data |
106 | * @buflen: Data length |
107 | * |
108 | **/ |
109 | static inline void sg_set_buf(struct scatterlist *sg, const void *buf, |
110 | unsigned int buflen) |
111 | { |
112 | sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf)); |
113 | } |
114 | |
115 | /* |
116 | * Loop over each sg element, following the pointer to a new list if necessary |
117 | */ |
118 | #define for_each_sg(sglist, sg, nr, __i) \ |
119 | for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg)) |
120 | |
121 | /** |
122 | * sg_chain - Chain two sglists together |
123 | * @prv: First scatterlist |
124 | * @prv_nents: Number of entries in prv |
125 | * @sgl: Second scatterlist |
126 | * |
127 | * Description: |
128 | * Links @prv@ and @sgl@ together, to form a longer scatterlist. |
129 | * |
130 | **/ |
131 | static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, |
132 | struct scatterlist *sgl) |
133 | { |
134 | #ifndef ARCH_HAS_SG_CHAIN |
135 | BUG(); |
136 | #endif |
137 | |
138 | /* |
139 | * offset and length are unused for chain entry. Clear them. |
140 | */ |
141 | prv[prv_nents - 1].offset = 0; |
142 | prv[prv_nents - 1].length = 0; |
143 | |
144 | /* |
145 | * Set lowest bit to indicate a link pointer, and make sure to clear |
146 | * the termination bit if it happens to be set. |
147 | */ |
148 | prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02; |
149 | } |
150 | |
151 | /** |
152 | * sg_mark_end - Mark the end of the scatterlist |
153 | * @sg: SG entryScatterlist |
154 | * |
155 | * Description: |
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. |
158 | * |
159 | **/ |
160 | static inline void sg_mark_end(struct scatterlist *sg) |
161 | { |
162 | #ifdef CONFIG_DEBUG_SG |
163 | BUG_ON(sg->sg_magic != SG_MAGIC); |
164 | #endif |
165 | /* |
166 | * Set termination bit, clear potential chain bit |
167 | */ |
168 | sg->page_link |= 0x02; |
169 | sg->page_link &= ~0x01; |
170 | } |
171 | |
172 | /** |
173 | * sg_phys - Return physical address of an sg entry |
174 | * @sg: SG entry |
175 | * |
176 | * Description: |
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() |
179 | * on the sg page. |
180 | * |
181 | **/ |
182 | static inline dma_addr_t sg_phys(struct scatterlist *sg) |
183 | { |
184 | return page_to_phys(sg_page(sg)) + sg->offset; |
185 | } |
186 | |
187 | /** |
188 | * sg_virt - Return virtual address of an sg entry |
189 | * @sg: SG entry |
190 | * |
191 | * Description: |
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 |
194 | * mapping. |
195 | * |
196 | **/ |
197 | static inline void *sg_virt(struct scatterlist *sg) |
198 | { |
199 | return page_address(sg_page(sg)) + sg->offset; |
200 | } |
201 | |
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); |
206 | |
207 | typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t); |
208 | typedef void (sg_free_fn)(struct scatterlist *, unsigned int); |
209 | |
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, |
213 | sg_alloc_fn *); |
214 | int sg_alloc_table(struct sg_table *, unsigned int, gfp_t); |
215 | |
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); |
220 | |
221 | /* |
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. |
224 | */ |
225 | #define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist)) |
226 | |
227 | |
228 | /* |
229 | * Mapping sg iterator |
230 | * |
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. |
236 | * |
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). |
242 | */ |
243 | |
244 | #define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */ |
245 | #define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */ |
246 | #define SG_MITER_FROM_SG (1 << 2) /* nop */ |
247 | |
248 | struct sg_mapping_iter { |
249 | /* the following three fields can be accessed directly */ |
250 | struct page *page; /* currently mapped page */ |
251 | void *addr; /* pointer to the mapped area */ |
252 | size_t length; /* length of the mapped area */ |
253 | size_t consumed; /* number of consumed bytes */ |
254 | |
255 | /* these are internal states, keep away */ |
256 | struct scatterlist *__sg; /* current entry */ |
257 | unsigned int __nents; /* nr of remaining entries */ |
258 | unsigned int __offset; /* offset within sg */ |
259 | unsigned int __flags; |
260 | }; |
261 | |
262 | void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, |
263 | unsigned int nents, unsigned int flags); |
264 | bool sg_miter_next(struct sg_mapping_iter *miter); |
265 | void sg_miter_stop(struct sg_mapping_iter *miter); |
266 | |
267 | #endif /* _LINUX_SCATTERLIST_H */ |
268 |
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