1#ifndef _LINUX_SCATTERLIST_H 2#define _LINUX_SCATTERLIST_H 3 4#include <linux/string.h> 5#include <linux/bug.h> 6#include <linux/mm.h> 7 8#include <asm/types.h> 9#include <asm/scatterlist.h> 10#include <asm/io.h> 11 12struct sg_table { 13 struct scatterlist *sgl; /* the list */ 14 unsigned int nents; /* number of mapped entries */ 15 unsigned int orig_nents; /* original size of list */ 16}; 17 18/* 19 * Notes on SG table design. 20 * 21 * Architectures must provide an unsigned long page_link field in the 22 * scatterlist struct. We use that to place the page pointer AND encode 23 * information about the sg table as well. The two lower bits are reserved 24 * for this information. 25 * 26 * If bit 0 is set, then the page_link contains a pointer to the next sg 27 * table list. Otherwise the next entry is at sg + 1. 28 * 29 * If bit 1 is set, then this sg entry is the last element in a list. 30 * 31 * See sg_next(). 32 * 33 */ 34 35#define SG_MAGIC 0x87654321 36 37/* 38 * We overload the LSB of the page pointer to indicate whether it's 39 * a valid sg entry, or whether it points to the start of a new scatterlist. 40 * Those low bits are there for everyone! (thanks mason :-) 41 */ 42#define sg_is_chain(sg) ((sg)->page_link & 0x01) 43#define sg_is_last(sg) ((sg)->page_link & 0x02) 44#define sg_chain_ptr(sg) \ 45 ((struct scatterlist *) ((sg)->page_link & ~0x03)) 46 47/** 48 * sg_assign_page - Assign a given page to an SG entry 49 * @sg: SG entry 50 * @page: The page 51 * 52 * Description: 53 * Assign page to sg entry. Also see sg_set_page(), the most commonly used 54 * variant. 55 * 56 **/ 57static inline void sg_assign_page(struct scatterlist *sg, struct page *page) 58{ 59 unsigned long page_link = sg->page_link & 0x3; 60 61 /* 62 * In order for the low bit stealing approach to work, pages 63 * must be aligned at a 32-bit boundary as a minimum. 64 */ 65 BUG_ON((unsigned long) page & 0x03); 66#ifdef CONFIG_DEBUG_SG 67 BUG_ON(sg->sg_magic != SG_MAGIC); 68 BUG_ON(sg_is_chain(sg)); 69#endif 70 sg->page_link = page_link | (unsigned long) page; 71} 72 73/** 74 * sg_set_page - Set sg entry to point at given page 75 * @sg: SG entry 76 * @page: The page 77 * @len: Length of data 78 * @offset: Offset into page 79 * 80 * Description: 81 * Use this function to set an sg entry pointing at a page, never assign 82 * the page directly. We encode sg table information in the lower bits 83 * of the page pointer. See sg_page() for looking up the page belonging 84 * to an sg entry. 85 * 86 **/ 87static inline void sg_set_page(struct scatterlist *sg, struct page *page, 88 unsigned int len, unsigned int offset) 89{ 90 sg_assign_page(sg, page); 91 sg->offset = offset; 92 sg->length = len; 93} 94 95static inline struct page *sg_page(struct scatterlist *sg) 96{ 97#ifdef CONFIG_DEBUG_SG 98 BUG_ON(sg->sg_magic != SG_MAGIC); 99 BUG_ON(sg_is_chain(sg)); 100#endif 101 return (struct page *)((sg)->page_link & ~0x3); 102} 103 104/** 105 * sg_set_buf - Set sg entry to point at given data 106 * @sg: SG entry 107 * @buf: Data 108 * @buflen: Data length 109 * 110 **/ 111static inline void sg_set_buf(struct scatterlist *sg, const void *buf, 112 unsigned int buflen) 113{ 114 sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf)); 115} 116 117/* 118 * Loop over each sg element, following the pointer to a new list if necessary 119 */ 120#define for_each_sg(sglist, sg, nr, __i) \ 121 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg)) 122 123/** 124 * sg_chain - Chain two sglists together 125 * @prv: First scatterlist 126 * @prv_nents: Number of entries in prv 127 * @sgl: Second scatterlist 128 * 129 * Description: 130 * Links @prv@ and @sgl@ together, to form a longer scatterlist. 131 * 132 **/ 133static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, 134 struct scatterlist *sgl) 135{ 136#ifndef ARCH_HAS_SG_CHAIN 137 BUG(); 138#endif 139 140 /* 141 * offset and length are unused for chain entry. Clear them. 142 */ 143 prv[prv_nents - 1].offset = 0; 144 prv[prv_nents - 1].length = 0; 145 146 /* 147 * Set lowest bit to indicate a link pointer, and make sure to clear 148 * the termination bit if it happens to be set. 149 */ 150 prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02; 151} 152 153/** 154 * sg_mark_end - Mark the end of the scatterlist 155 * @sg: SG entryScatterlist 156 * 157 * Description: 158 * Marks the passed in sg entry as the termination point for the sg 159 * table. A call to sg_next() on this entry will return NULL. 160 * 161 **/ 162static inline void sg_mark_end(struct scatterlist *sg) 163{ 164#ifdef CONFIG_DEBUG_SG 165 BUG_ON(sg->sg_magic != SG_MAGIC); 166#endif 167 /* 168 * Set termination bit, clear potential chain bit 169 */ 170 sg->page_link |= 0x02; 171 sg->page_link &= ~0x01; 172} 173 174/** 175 * sg_phys - Return physical address of an sg entry 176 * @sg: SG entry 177 * 178 * Description: 179 * This calls page_to_phys() on the page in this sg entry, and adds the 180 * sg offset. The caller must know that it is legal to call page_to_phys() 181 * on the sg page. 182 * 183 **/ 184static inline dma_addr_t sg_phys(struct scatterlist *sg) 185{ 186 return page_to_phys(sg_page(sg)) + sg->offset; 187} 188 189/** 190 * sg_virt - Return virtual address of an sg entry 191 * @sg: SG entry 192 * 193 * Description: 194 * This calls page_address() on the page in this sg entry, and adds the 195 * sg offset. The caller must know that the sg page has a valid virtual 196 * mapping. 197 * 198 **/ 199static inline void *sg_virt(struct scatterlist *sg) 200{ 201 return page_address(sg_page(sg)) + sg->offset; 202} 203 204struct scatterlist *sg_next(struct scatterlist *); 205struct scatterlist *sg_last(struct scatterlist *s, unsigned int); 206void sg_init_table(struct scatterlist *, unsigned int); 207void sg_init_one(struct scatterlist *, const void *, unsigned int); 208 209typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t); 210typedef void (sg_free_fn)(struct scatterlist *, unsigned int); 211 212void __sg_free_table(struct sg_table *, unsigned int, sg_free_fn *); 213void sg_free_table(struct sg_table *); 214int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, gfp_t, 215 sg_alloc_fn *); 216int sg_alloc_table(struct sg_table *, unsigned int, gfp_t); 217 218size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, 219 void *buf, size_t buflen); 220size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, 221 void *buf, size_t buflen); 222 223/* 224 * Maximum number of entries that will be allocated in one piece, if 225 * a list larger than this is required then chaining will be utilized. 226 */ 227#define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist)) 228 229 230/* 231 * Mapping sg iterator 232 * 233 * Iterates over sg entries mapping page-by-page. On each successful 234 * iteration, @miter->page points to the mapped page and 235 * @miter->length bytes of data can be accessed at @miter->addr. As 236 * long as an interation is enclosed between start and stop, the user 237 * is free to choose control structure and when to stop. 238 * 239 * @miter->consumed is set to @miter->length on each iteration. It 240 * can be adjusted if the user can't consume all the bytes in one go. 241 * Also, a stopped iteration can be resumed by calling next on it. 242 * This is useful when iteration needs to release all resources and 243 * continue later (e.g. at the next interrupt). 244 */ 245 246#define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */ 247#define SG_MITER_TO_SG (1 << 1) /* flush back to phys on unmap */ 248#define SG_MITER_FROM_SG (1 << 2) /* nop */ 249 250struct sg_mapping_iter { 251 /* the following three fields can be accessed directly */ 252 struct page *page; /* currently mapped page */ 253 void *addr; /* pointer to the mapped area */ 254 size_t length; /* length of the mapped area */ 255 size_t consumed; /* number of consumed bytes */ 256 257 /* these are internal states, keep away */ 258 struct scatterlist *__sg; /* current entry */ 259 unsigned int __nents; /* nr of remaining entries */ 260 unsigned int __offset; /* offset within sg */ 261 unsigned int __flags; 262}; 263 264void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, 265 unsigned int nents, unsigned int flags); 266bool sg_miter_next(struct sg_mapping_iter *miter); 267void sg_miter_stop(struct sg_mapping_iter *miter); 268 269#endif /* _LINUX_SCATTERLIST_H */ 270