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