1 /* SPDX-License-Identifier: GPL-2.0 */
4 #include <linux/kernel.h>
8 unsigned long page_link;
11 dma_addr_t dma_address;
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))
21 * sg_assign_page - Assign a given page to an SG entry
26 * Assign page to sg entry. Also see sg_set_page(), the most commonly used
30 static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
32 unsigned long page_link = sg->page_link & 0x3;
35 * In order for the low bit stealing approach to work, pages
36 * must be aligned at a 32-bit boundary as a minimum.
38 BUG_ON((unsigned long) page & 0x03);
39 #ifdef CONFIG_DEBUG_SG
40 BUG_ON(sg->sg_magic != SG_MAGIC);
41 BUG_ON(sg_is_chain(sg));
43 sg->page_link = page_link | (unsigned long) page;
47 * sg_set_page - Set sg entry to point at given page
50 * @len: Length of data
51 * @offset: Offset into page
54 * Use this function to set an sg entry pointing at a page, never assign
55 * the page directly. We encode sg table information in the lower bits
56 * of the page pointer. See sg_page() for looking up the page belonging
60 static inline void sg_set_page(struct scatterlist *sg, struct page *page,
61 unsigned int len, unsigned int offset)
63 sg_assign_page(sg, page);
68 static inline struct page *sg_page(struct scatterlist *sg)
70 #ifdef CONFIG_DEBUG_SG
71 BUG_ON(sg->sg_magic != SG_MAGIC);
72 BUG_ON(sg_is_chain(sg));
74 return (struct page *)((sg)->page_link & ~0x3);
78 * Loop over each sg element, following the pointer to a new list if necessary
80 #define for_each_sg(sglist, sg, nr, __i) \
81 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
84 * sg_chain - Chain two sglists together
85 * @prv: First scatterlist
86 * @prv_nents: Number of entries in prv
87 * @sgl: Second scatterlist
90 * Links @prv@ and @sgl@ together, to form a longer scatterlist.
93 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
94 struct scatterlist *sgl)
97 * offset and length are unused for chain entry. Clear them.
99 prv[prv_nents - 1].offset = 0;
100 prv[prv_nents - 1].length = 0;
103 * Set lowest bit to indicate a link pointer, and make sure to clear
104 * the termination bit if it happens to be set.
106 prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
110 * sg_mark_end - Mark the end of the scatterlist
111 * @sg: SG entryScatterlist
114 * Marks the passed in sg entry as the termination point for the sg
115 * table. A call to sg_next() on this entry will return NULL.
118 static inline void sg_mark_end(struct scatterlist *sg)
120 #ifdef CONFIG_DEBUG_SG
121 BUG_ON(sg->sg_magic != SG_MAGIC);
124 * Set termination bit, clear potential chain bit
126 sg->page_link |= 0x02;
127 sg->page_link &= ~0x01;
131 * sg_unmark_end - Undo setting the end of the scatterlist
132 * @sg: SG entryScatterlist
135 * Removes the termination marker from the given entry of the scatterlist.
138 static inline void sg_unmark_end(struct scatterlist *sg)
140 #ifdef CONFIG_DEBUG_SG
141 BUG_ON(sg->sg_magic != SG_MAGIC);
143 sg->page_link &= ~0x02;
146 static inline struct scatterlist *sg_next(struct scatterlist *sg)
148 #ifdef CONFIG_DEBUG_SG
149 BUG_ON(sg->sg_magic != SG_MAGIC);
155 if (unlikely(sg_is_chain(sg)))
156 sg = sg_chain_ptr(sg);
161 static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents)
163 memset(sgl, 0, sizeof(*sgl) * nents);
164 #ifdef CONFIG_DEBUG_SG
167 for (i = 0; i < nents; i++)
168 sgl[i].sg_magic = SG_MAGIC;
171 sg_mark_end(&sgl[nents - 1]);
174 static inline dma_addr_t sg_phys(struct scatterlist *sg)
176 return page_to_phys(sg_page(sg)) + sg->offset;
179 static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
182 sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
185 static inline void sg_init_one(struct scatterlist *sg,
186 const void *buf, unsigned int buflen)
188 sg_init_table(sg, 1);
189 sg_set_buf(sg, buf, buflen);
191 #endif /* SCATTERLIST_H */