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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef SCATTERLIST_H
3#define SCATTERLIST_H
4#include <linux/kernel.h>
5
6struct 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 **/
29static 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->sg_magic != SG_MAGIC);
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 **/
59static 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
67static inline struct page *sg_page(struct scatterlist *sg)
68{
69#ifdef CONFIG_DEBUG_SG
70 BUG_ON(sg->sg_magic != SG_MAGIC);
71 BUG_ON(sg_is_chain(sg));
72#endif
73 return (struct page *)((sg)->page_link & ~0x3);
74}
75
76/*
77 * Loop over each sg element, following the pointer to a new list if necessary
78 */
79#define for_each_sg(sglist, sg, nr, __i) \
80 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
81
82/**
83 * sg_chain - Chain two sglists together
84 * @prv: First scatterlist
85 * @prv_nents: Number of entries in prv
86 * @sgl: Second scatterlist
87 *
88 * Description:
89 * Links @prv@ and @sgl@ together, to form a longer scatterlist.
90 *
91 **/
92static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
93 struct scatterlist *sgl)
94{
95 /*
96 * offset and length are unused for chain entry. Clear them.
97 */
98 prv[prv_nents - 1].offset = 0;
99 prv[prv_nents - 1].length = 0;
100
101 /*
102 * Set lowest bit to indicate a link pointer, and make sure to clear
103 * the termination bit if it happens to be set.
104 */
105 prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
106}
107
108/**
109 * sg_mark_end - Mark the end of the scatterlist
110 * @sg: SG entryScatterlist
111 *
112 * Description:
113 * Marks the passed in sg entry as the termination point for the sg
114 * table. A call to sg_next() on this entry will return NULL.
115 *
116 **/
117static inline void sg_mark_end(struct scatterlist *sg)
118{
119#ifdef CONFIG_DEBUG_SG
120 BUG_ON(sg->sg_magic != SG_MAGIC);
121#endif
122 /*
123 * Set termination bit, clear potential chain bit
124 */
125 sg->page_link |= 0x02;
126 sg->page_link &= ~0x01;
127}
128
129/**
130 * sg_unmark_end - Undo setting the end of the scatterlist
131 * @sg: SG entryScatterlist
132 *
133 * Description:
134 * Removes the termination marker from the given entry of the scatterlist.
135 *
136 **/
137static inline void sg_unmark_end(struct scatterlist *sg)
138{
139#ifdef CONFIG_DEBUG_SG
140 BUG_ON(sg->sg_magic != SG_MAGIC);
141#endif
142 sg->page_link &= ~0x02;
143}
144
145static inline struct scatterlist *sg_next(struct scatterlist *sg)
146{
147#ifdef CONFIG_DEBUG_SG
148 BUG_ON(sg->sg_magic != SG_MAGIC);
149#endif
150 if (sg_is_last(sg))
151 return NULL;
152
153 sg++;
154 if (unlikely(sg_is_chain(sg)))
155 sg = sg_chain_ptr(sg);
156
157 return sg;
158}
159
160static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents)
161{
162 memset(sgl, 0, sizeof(*sgl) * nents);
163#ifdef CONFIG_DEBUG_SG
164 {
165 unsigned int i;
166 for (i = 0; i < nents; i++)
167 sgl[i].sg_magic = SG_MAGIC;
168 }
169#endif
170 sg_mark_end(&sgl[nents - 1]);
171}
172
173static inline dma_addr_t sg_phys(struct scatterlist *sg)
174{
175 return page_to_phys(sg_page(sg)) + sg->offset;
176}
177
178static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
179 unsigned int buflen)
180{
181 sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
182}
183
184static inline void sg_init_one(struct scatterlist *sg,
185 const void *buf, unsigned int buflen)
186{
187 sg_init_table(sg, 1);
188 sg_set_buf(sg, buf, buflen);
189}
190#endif /* SCATTERLIST_H */