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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 | #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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