| 1 | #ifndef _LINUX_SCATTERLIST_H |
| 2 | #define _LINUX_SCATTERLIST_H |
| 3 | |
| 4 | #include <asm/scatterlist.h> |
| 5 | #include <linux/mm.h> |
| 6 | #include <linux/string.h> |
| 7 | #include <asm/io.h> |
| 8 | |
| 9 | /* |
| 10 | * Notes on SG table design. |
| 11 | * |
| 12 | * Architectures must provide an unsigned long page_link field in the |
| 13 | * scatterlist struct. We use that to place the page pointer AND encode |
| 14 | * information about the sg table as well. The two lower bits are reserved |
| 15 | * for this information. |
| 16 | * |
| 17 | * If bit 0 is set, then the page_link contains a pointer to the next sg |
| 18 | * table list. Otherwise the next entry is at sg + 1. |
| 19 | * |
| 20 | * If bit 1 is set, then this sg entry is the last element in a list. |
| 21 | * |
| 22 | * See sg_next(). |
| 23 | * |
| 24 | */ |
| 25 | |
| 26 | #define SG_MAGIC 0x87654321 |
| 27 | |
| 28 | /** |
| 29 | * sg_set_page - Set sg entry to point at given page |
| 30 | * @sg: SG entry |
| 31 | * @page: The page |
| 32 | * |
| 33 | * Description: |
| 34 | * Use this function to set an sg entry pointing at a page, never assign |
| 35 | * the page directly. We encode sg table information in the lower bits |
| 36 | * of the page pointer. See sg_page() for looking up the page belonging |
| 37 | * to an sg entry. |
| 38 | * |
| 39 | **/ |
| 40 | static inline void sg_set_page(struct scatterlist *sg, struct page *page) |
| 41 | { |
| 42 | unsigned long page_link = sg->page_link & 0x3; |
| 43 | |
| 44 | #ifdef CONFIG_DEBUG_SG |
| 45 | BUG_ON(sg->sg_magic != SG_MAGIC); |
| 46 | #endif |
| 47 | sg->page_link = page_link | (unsigned long) page; |
| 48 | } |
| 49 | |
| 50 | #define sg_page(sg) ((struct page *) ((sg)->page_link & ~0x3)) |
| 51 | |
| 52 | /** |
| 53 | * sg_set_buf - Set sg entry to point at given data |
| 54 | * @sg: SG entry |
| 55 | * @buf: Data |
| 56 | * @buflen: Data length |
| 57 | * |
| 58 | **/ |
| 59 | static inline void sg_set_buf(struct scatterlist *sg, const void *buf, |
| 60 | unsigned int buflen) |
| 61 | { |
| 62 | sg_set_page(sg, virt_to_page(buf)); |
| 63 | sg->offset = offset_in_page(buf); |
| 64 | sg->length = buflen; |
| 65 | } |
| 66 | |
| 67 | /* |
| 68 | * We overload the LSB of the page pointer to indicate whether it's |
| 69 | * a valid sg entry, or whether it points to the start of a new scatterlist. |
| 70 | * Those low bits are there for everyone! (thanks mason :-) |
| 71 | */ |
| 72 | #define sg_is_chain(sg) ((sg)->page_link & 0x01) |
| 73 | #define sg_is_last(sg) ((sg)->page_link & 0x02) |
| 74 | #define sg_chain_ptr(sg) \ |
| 75 | ((struct scatterlist *) ((sg)->page_link & ~0x03)) |
| 76 | |
| 77 | /** |
| 78 | * sg_next - return the next scatterlist entry in a list |
| 79 | * @sg: The current sg entry |
| 80 | * |
| 81 | * Description: |
| 82 | * Usually the next entry will be @sg@ + 1, but if this sg element is part |
| 83 | * of a chained scatterlist, it could jump to the start of a new |
| 84 | * scatterlist array. |
| 85 | * |
| 86 | **/ |
| 87 | static inline struct scatterlist *sg_next(struct scatterlist *sg) |
| 88 | { |
| 89 | #ifdef CONFIG_DEBUG_SG |
| 90 | BUG_ON(sg->sg_magic != SG_MAGIC); |
| 91 | #endif |
| 92 | if (sg_is_last(sg)) |
| 93 | return NULL; |
| 94 | |
| 95 | sg++; |
| 96 | if (unlikely(sg_is_chain(sg))) |
| 97 | sg = sg_chain_ptr(sg); |
| 98 | |
| 99 | return sg; |
| 100 | } |
| 101 | |
| 102 | /* |
| 103 | * Loop over each sg element, following the pointer to a new list if necessary |
| 104 | */ |
| 105 | #define for_each_sg(sglist, sg, nr, __i) \ |
| 106 | for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg)) |
| 107 | |
| 108 | /** |
| 109 | * sg_last - return the last scatterlist entry in a list |
| 110 | * @sgl: First entry in the scatterlist |
| 111 | * @nents: Number of entries in the scatterlist |
| 112 | * |
| 113 | * Description: |
| 114 | * Should only be used casually, it (currently) scan the entire list |
| 115 | * to get the last entry. |
| 116 | * |
| 117 | * Note that the @sgl@ pointer passed in need not be the first one, |
| 118 | * the important bit is that @nents@ denotes the number of entries that |
| 119 | * exist from @sgl@. |
| 120 | * |
| 121 | **/ |
| 122 | static inline struct scatterlist *sg_last(struct scatterlist *sgl, |
| 123 | unsigned int nents) |
| 124 | { |
| 125 | #ifndef ARCH_HAS_SG_CHAIN |
| 126 | struct scatterlist *ret = &sgl[nents - 1]; |
| 127 | #else |
| 128 | struct scatterlist *sg, *ret = NULL; |
| 129 | int i; |
| 130 | |
| 131 | for_each_sg(sgl, sg, nents, i) |
| 132 | ret = sg; |
| 133 | |
| 134 | #endif |
| 135 | #ifdef CONFIG_DEBUG_SG |
| 136 | BUG_ON(sgl[0].sg_magic != SG_MAGIC); |
| 137 | BUG_ON(!sg_is_last(ret)); |
| 138 | #endif |
| 139 | return ret; |
| 140 | } |
| 141 | |
| 142 | /** |
| 143 | * sg_chain - Chain two sglists together |
| 144 | * @prv: First scatterlist |
| 145 | * @prv_nents: Number of entries in prv |
| 146 | * @sgl: Second scatterlist |
| 147 | * |
| 148 | * Description: |
| 149 | * Links @prv@ and @sgl@ together, to form a longer scatterlist. |
| 150 | * |
| 151 | **/ |
| 152 | static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, |
| 153 | struct scatterlist *sgl) |
| 154 | { |
| 155 | #ifndef ARCH_HAS_SG_CHAIN |
| 156 | BUG(); |
| 157 | #endif |
| 158 | prv[prv_nents - 1].page_link = (unsigned long) sgl | 0x01; |
| 159 | } |
| 160 | |
| 161 | /** |
| 162 | * sg_mark_end - Mark the end of the scatterlist |
| 163 | * @sgl: Scatterlist |
| 164 | * @nents: Number of entries in sgl |
| 165 | * |
| 166 | * Description: |
| 167 | * Marks the last entry as the termination point for sg_next() |
| 168 | * |
| 169 | **/ |
| 170 | static inline void sg_mark_end(struct scatterlist *sgl, unsigned int nents) |
| 171 | { |
| 172 | sgl[nents - 1].page_link = 0x02; |
| 173 | } |
| 174 | |
| 175 | static inline void __sg_mark_end(struct scatterlist *sg) |
| 176 | { |
| 177 | sg->page_link |= 0x02; |
| 178 | } |
| 179 | |
| 180 | /** |
| 181 | * sg_init_one - Initialize a single entry sg list |
| 182 | * @sg: SG entry |
| 183 | * @buf: Virtual address for IO |
| 184 | * @buflen: IO length |
| 185 | * |
| 186 | * Notes: |
| 187 | * This should not be used on a single entry that is part of a larger |
| 188 | * table. Use sg_init_table() for that. |
| 189 | * |
| 190 | **/ |
| 191 | static inline void sg_init_one(struct scatterlist *sg, const void *buf, |
| 192 | unsigned int buflen) |
| 193 | { |
| 194 | memset(sg, 0, sizeof(*sg)); |
| 195 | #ifdef CONFIG_DEBUG_SG |
| 196 | sg->sg_magic = SG_MAGIC; |
| 197 | #endif |
| 198 | sg_mark_end(sg, 1); |
| 199 | sg_set_buf(sg, buf, buflen); |
| 200 | } |
| 201 | |
| 202 | /** |
| 203 | * sg_init_table - Initialize SG table |
| 204 | * @sgl: The SG table |
| 205 | * @nents: Number of entries in table |
| 206 | * |
| 207 | * Notes: |
| 208 | * If this is part of a chained sg table, sg_mark_end() should be |
| 209 | * used only on the last table part. |
| 210 | * |
| 211 | **/ |
| 212 | static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents) |
| 213 | { |
| 214 | memset(sgl, 0, sizeof(*sgl) * nents); |
| 215 | sg_mark_end(sgl, nents); |
| 216 | #ifdef CONFIG_DEBUG_SG |
| 217 | { |
| 218 | int i; |
| 219 | for (i = 0; i < nents; i++) |
| 220 | sgl[i].sg_magic = SG_MAGIC; |
| 221 | } |
| 222 | #endif |
| 223 | } |
| 224 | |
| 225 | /** |
| 226 | * sg_phys - Return physical address of an sg entry |
| 227 | * @sg: SG entry |
| 228 | * |
| 229 | * Description: |
| 230 | * This calls page_to_phys() on the page in this sg entry, and adds the |
| 231 | * sg offset. The caller must know that it is legal to call page_to_phys() |
| 232 | * on the sg page. |
| 233 | * |
| 234 | **/ |
| 235 | static inline unsigned long sg_phys(struct scatterlist *sg) |
| 236 | { |
| 237 | return page_to_phys(sg_page(sg)) + sg->offset; |
| 238 | } |
| 239 | |
| 240 | /** |
| 241 | * sg_virt - Return virtual address of an sg entry |
| 242 | * @sg: SG entry |
| 243 | * |
| 244 | * Description: |
| 245 | * This calls page_address() on the page in this sg entry, and adds the |
| 246 | * sg offset. The caller must know that the sg page has a valid virtual |
| 247 | * mapping. |
| 248 | * |
| 249 | **/ |
| 250 | static inline void *sg_virt(struct scatterlist *sg) |
| 251 | { |
| 252 | return page_address(sg_page(sg)) + sg->offset; |
| 253 | } |
| 254 | |
| 255 | #endif /* _LINUX_SCATTERLIST_H */ |