1 /* SPDX-License-Identifier: GPL-2.0 */
4 #include <linux/kernel.h>
7 unsigned long page_link;
10 dma_addr_t dma_address;
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))
20 * sg_assign_page - Assign a given page to an SG entry
25 * Assign page to sg entry. Also see sg_set_page(), the most commonly used
29 static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
31 unsigned long page_link = sg->page_link & 0x3;
34 * In order for the low bit stealing approach to work, pages
35 * must be aligned at a 32-bit boundary as a minimum.
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));
42 sg->page_link = page_link | (unsigned long) page;
46 * sg_set_page - Set sg entry to point at given page
49 * @len: Length of data
50 * @offset: Offset into page
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
59 static inline void sg_set_page(struct scatterlist *sg, struct page *page,
60 unsigned int len, unsigned int offset)
62 sg_assign_page(sg, page);
67 static inline struct page *sg_page(struct scatterlist *sg)
69 #ifdef CONFIG_DEBUG_SG
70 BUG_ON(sg->sg_magic != SG_MAGIC);
71 BUG_ON(sg_is_chain(sg));
73 return (struct page *)((sg)->page_link & ~0x3);
77 * Loop over each sg element, following the pointer to a new list if necessary
79 #define for_each_sg(sglist, sg, nr, __i) \
80 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
83 * sg_chain - Chain two sglists together
84 * @prv: First scatterlist
85 * @prv_nents: Number of entries in prv
86 * @sgl: Second scatterlist
89 * Links @prv@ and @sgl@ together, to form a longer scatterlist.
92 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
93 struct scatterlist *sgl)
96 * offset and length are unused for chain entry. Clear them.
98 prv[prv_nents - 1].offset = 0;
99 prv[prv_nents - 1].length = 0;
102 * Set lowest bit to indicate a link pointer, and make sure to clear
103 * the termination bit if it happens to be set.
105 prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
109 * sg_mark_end - Mark the end of the scatterlist
110 * @sg: SG entryScatterlist
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.
117 static inline void sg_mark_end(struct scatterlist *sg)
119 #ifdef CONFIG_DEBUG_SG
120 BUG_ON(sg->sg_magic != SG_MAGIC);
123 * Set termination bit, clear potential chain bit
125 sg->page_link |= 0x02;
126 sg->page_link &= ~0x01;
130 * sg_unmark_end - Undo setting the end of the scatterlist
131 * @sg: SG entryScatterlist
134 * Removes the termination marker from the given entry of the scatterlist.
137 static inline void sg_unmark_end(struct scatterlist *sg)
139 #ifdef CONFIG_DEBUG_SG
140 BUG_ON(sg->sg_magic != SG_MAGIC);
142 sg->page_link &= ~0x02;
145 static inline struct scatterlist *sg_next(struct scatterlist *sg)
147 #ifdef CONFIG_DEBUG_SG
148 BUG_ON(sg->sg_magic != SG_MAGIC);
154 if (unlikely(sg_is_chain(sg)))
155 sg = sg_chain_ptr(sg);
160 static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents)
162 memset(sgl, 0, sizeof(*sgl) * nents);
163 #ifdef CONFIG_DEBUG_SG
166 for (i = 0; i < nents; i++)
167 sgl[i].sg_magic = SG_MAGIC;
170 sg_mark_end(&sgl[nents - 1]);
173 static inline dma_addr_t sg_phys(struct scatterlist *sg)
175 return page_to_phys(sg_page(sg)) + sg->offset;
178 static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
181 sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
184 static inline void sg_init_one(struct scatterlist *sg,
185 const void *buf, unsigned int buflen)
187 sg_init_table(sg, 1);
188 sg_set_buf(sg, buf, buflen);
190 #endif /* SCATTERLIST_H */