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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
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2 | #ifndef SCATTERLIST_H |
3 | #define SCATTERLIST_H | |
4 | #include <linux/kernel.h> | |
3f7b75ab | 5 | #include <linux/bug.h> |
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6 | |
7 | struct scatterlist { | |
8 | unsigned long page_link; | |
9 | unsigned int offset; | |
10 | unsigned int length; | |
11 | dma_addr_t dma_address; | |
12 | }; | |
13 | ||
14 | /* Scatterlist helpers, stolen from linux/scatterlist.h */ | |
15 | #define sg_is_chain(sg) ((sg)->page_link & 0x01) | |
16 | #define sg_is_last(sg) ((sg)->page_link & 0x02) | |
17 | #define sg_chain_ptr(sg) \ | |
18 | ((struct scatterlist *) ((sg)->page_link & ~0x03)) | |
19 | ||
20 | /** | |
21 | * sg_assign_page - Assign a given page to an SG entry | |
22 | * @sg: SG entry | |
23 | * @page: The page | |
24 | * | |
25 | * Description: | |
26 | * Assign page to sg entry. Also see sg_set_page(), the most commonly used | |
27 | * variant. | |
28 | * | |
29 | **/ | |
30 | static inline void sg_assign_page(struct scatterlist *sg, struct page *page) | |
31 | { | |
32 | unsigned long page_link = sg->page_link & 0x3; | |
33 | ||
34 | /* | |
35 | * In order for the low bit stealing approach to work, pages | |
36 | * must be aligned at a 32-bit boundary as a minimum. | |
37 | */ | |
38 | BUG_ON((unsigned long) page & 0x03); | |
39 | #ifdef CONFIG_DEBUG_SG | |
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40 | BUG_ON(sg_is_chain(sg)); |
41 | #endif | |
42 | sg->page_link = page_link | (unsigned long) page; | |
43 | } | |
44 | ||
45 | /** | |
46 | * sg_set_page - Set sg entry to point at given page | |
47 | * @sg: SG entry | |
48 | * @page: The page | |
49 | * @len: Length of data | |
50 | * @offset: Offset into page | |
51 | * | |
52 | * Description: | |
53 | * Use this function to set an sg entry pointing at a page, never assign | |
54 | * the page directly. We encode sg table information in the lower bits | |
55 | * of the page pointer. See sg_page() for looking up the page belonging | |
56 | * to an sg entry. | |
57 | * | |
58 | **/ | |
59 | static inline void sg_set_page(struct scatterlist *sg, struct page *page, | |
60 | unsigned int len, unsigned int offset) | |
61 | { | |
62 | sg_assign_page(sg, page); | |
63 | sg->offset = offset; | |
64 | sg->length = len; | |
65 | } | |
66 | ||
67 | static inline struct page *sg_page(struct scatterlist *sg) | |
68 | { | |
69 | #ifdef CONFIG_DEBUG_SG | |
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70 | BUG_ON(sg_is_chain(sg)); |
71 | #endif | |
72 | return (struct page *)((sg)->page_link & ~0x3); | |
73 | } | |
74 | ||
75 | /* | |
76 | * Loop over each sg element, following the pointer to a new list if necessary | |
77 | */ | |
78 | #define for_each_sg(sglist, sg, nr, __i) \ | |
79 | for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg)) | |
80 | ||
81 | /** | |
82 | * sg_chain - Chain two sglists together | |
83 | * @prv: First scatterlist | |
84 | * @prv_nents: Number of entries in prv | |
85 | * @sgl: Second scatterlist | |
86 | * | |
87 | * Description: | |
88 | * Links @prv@ and @sgl@ together, to form a longer scatterlist. | |
89 | * | |
90 | **/ | |
91 | static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, | |
92 | struct scatterlist *sgl) | |
93 | { | |
94 | /* | |
95 | * offset and length are unused for chain entry. Clear them. | |
96 | */ | |
97 | prv[prv_nents - 1].offset = 0; | |
98 | prv[prv_nents - 1].length = 0; | |
99 | ||
100 | /* | |
101 | * Set lowest bit to indicate a link pointer, and make sure to clear | |
102 | * the termination bit if it happens to be set. | |
103 | */ | |
104 | prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02; | |
105 | } | |
106 | ||
107 | /** | |
108 | * sg_mark_end - Mark the end of the scatterlist | |
109 | * @sg: SG entryScatterlist | |
110 | * | |
111 | * Description: | |
112 | * Marks the passed in sg entry as the termination point for the sg | |
113 | * table. A call to sg_next() on this entry will return NULL. | |
114 | * | |
115 | **/ | |
116 | static inline void sg_mark_end(struct scatterlist *sg) | |
117 | { | |
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118 | /* |
119 | * Set termination bit, clear potential chain bit | |
120 | */ | |
121 | sg->page_link |= 0x02; | |
122 | sg->page_link &= ~0x01; | |
123 | } | |
124 | ||
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125 | /** |
126 | * sg_unmark_end - Undo setting the end of the scatterlist | |
127 | * @sg: SG entryScatterlist | |
128 | * | |
129 | * Description: | |
130 | * Removes the termination marker from the given entry of the scatterlist. | |
131 | * | |
132 | **/ | |
133 | static inline void sg_unmark_end(struct scatterlist *sg) | |
134 | { | |
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135 | sg->page_link &= ~0x02; |
136 | } | |
137 | ||
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138 | static inline struct scatterlist *sg_next(struct scatterlist *sg) |
139 | { | |
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140 | if (sg_is_last(sg)) |
141 | return NULL; | |
142 | ||
143 | sg++; | |
144 | if (unlikely(sg_is_chain(sg))) | |
145 | sg = sg_chain_ptr(sg); | |
146 | ||
147 | return sg; | |
148 | } | |
149 | ||
150 | static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents) | |
151 | { | |
152 | memset(sgl, 0, sizeof(*sgl) * nents); | |
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153 | sg_mark_end(&sgl[nents - 1]); |
154 | } | |
155 | ||
156 | static inline dma_addr_t sg_phys(struct scatterlist *sg) | |
157 | { | |
158 | return page_to_phys(sg_page(sg)) + sg->offset; | |
159 | } | |
160 | ||
161 | static inline void sg_set_buf(struct scatterlist *sg, const void *buf, | |
162 | unsigned int buflen) | |
163 | { | |
164 | sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf)); | |
165 | } | |
166 | ||
167 | static inline void sg_init_one(struct scatterlist *sg, | |
168 | const void *buf, unsigned int buflen) | |
169 | { | |
170 | sg_init_table(sg, 1); | |
171 | sg_set_buf(sg, buf, buflen); | |
172 | } | |
173 | #endif /* SCATTERLIST_H */ |