1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef SCATTERLIST_H
3 #define SCATTERLIST_H
4 #include <linux/kernel.h>
5 #include <linux/bug.h>
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
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
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 {
118 /*
119 * Set termination bit, clear potential chain bit
120 */
121 sg->page_link |= 0x02;
122 sg->page_link &= ~0x01;
123 }
124
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 {
135 sg->page_link &= ~0x02;
136 }
137
138 static inline struct scatterlist *sg_next(struct scatterlist *sg)
139 {
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);
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 */
174
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