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Linus Torvalds1da177e2005-04-16 15:20:36 -07001#ifndef _LINUX_SCATTERLIST_H
2#define _LINUX_SCATTERLIST_H
3
Hugh Dickins85cdffc2007-10-25 09:55:05 +02004#include <asm/types.h>
Herbert Xud32311f2005-09-17 14:41:40 +10005#include <asm/scatterlist.h>
6#include <linux/mm.h>
7#include <linux/string.h>
Jens Axboe18dabf42007-10-22 19:57:20 +02008#include <asm/io.h>
9
Jens Axboe0db92992007-11-30 09:16:50 +010010struct sg_table {
11 struct scatterlist *sgl; /* the list */
12 unsigned int nents; /* number of mapped entries */
13 unsigned int orig_nents; /* original size of list */
14};
15
Jens Axboe18dabf42007-10-22 19:57:20 +020016/*
17 * Notes on SG table design.
18 *
19 * Architectures must provide an unsigned long page_link field in the
20 * scatterlist struct. We use that to place the page pointer AND encode
21 * information about the sg table as well. The two lower bits are reserved
22 * for this information.
23 *
24 * If bit 0 is set, then the page_link contains a pointer to the next sg
25 * table list. Otherwise the next entry is at sg + 1.
26 *
27 * If bit 1 is set, then this sg entry is the last element in a list.
28 *
29 * See sg_next().
30 *
31 */
Linus Torvalds1da177e2005-04-16 15:20:36 -070032
Jens Axboed6ec0842007-10-22 20:01:06 +020033#define SG_MAGIC 0x87654321
34
Tejun Heo645a8d92007-11-27 09:30:39 +010035/*
36 * We overload the LSB of the page pointer to indicate whether it's
37 * a valid sg entry, or whether it points to the start of a new scatterlist.
38 * Those low bits are there for everyone! (thanks mason :-)
39 */
40#define sg_is_chain(sg) ((sg)->page_link & 0x01)
41#define sg_is_last(sg) ((sg)->page_link & 0x02)
42#define sg_chain_ptr(sg) \
43 ((struct scatterlist *) ((sg)->page_link & ~0x03))
44
Jens Axboe82f66fb2007-10-22 17:07:37 +020045/**
Jens Axboe642f1492007-10-24 11:20:47 +020046 * sg_assign_page - Assign a given page to an SG entry
47 * @sg: SG entry
48 * @page: The page
Jens Axboe82f66fb2007-10-22 17:07:37 +020049 *
50 * Description:
Jens Axboe642f1492007-10-24 11:20:47 +020051 * Assign page to sg entry. Also see sg_set_page(), the most commonly used
52 * variant.
Jens Axboe82f66fb2007-10-22 17:07:37 +020053 *
54 **/
Jens Axboe642f1492007-10-24 11:20:47 +020055static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
Jens Axboe82f66fb2007-10-22 17:07:37 +020056{
Jens Axboe18dabf42007-10-22 19:57:20 +020057 unsigned long page_link = sg->page_link & 0x3;
58
Jens Axboede261032007-10-23 20:35:58 +020059 /*
60 * In order for the low bit stealing approach to work, pages
61 * must be aligned at a 32-bit boundary as a minimum.
62 */
63 BUG_ON((unsigned long) page & 0x03);
Jens Axboed6ec0842007-10-22 20:01:06 +020064#ifdef CONFIG_DEBUG_SG
65 BUG_ON(sg->sg_magic != SG_MAGIC);
Tejun Heo645a8d92007-11-27 09:30:39 +010066 BUG_ON(sg_is_chain(sg));
Jens Axboed6ec0842007-10-22 20:01:06 +020067#endif
Jens Axboe18dabf42007-10-22 19:57:20 +020068 sg->page_link = page_link | (unsigned long) page;
Jens Axboe82f66fb2007-10-22 17:07:37 +020069}
70
Jens Axboe642f1492007-10-24 11:20:47 +020071/**
72 * sg_set_page - Set sg entry to point at given page
73 * @sg: SG entry
74 * @page: The page
75 * @len: Length of data
76 * @offset: Offset into page
77 *
78 * Description:
79 * Use this function to set an sg entry pointing at a page, never assign
80 * the page directly. We encode sg table information in the lower bits
81 * of the page pointer. See sg_page() for looking up the page belonging
82 * to an sg entry.
83 *
84 **/
85static inline void sg_set_page(struct scatterlist *sg, struct page *page,
86 unsigned int len, unsigned int offset)
87{
88 sg_assign_page(sg, page);
89 sg->offset = offset;
90 sg->length = len;
91}
92
Tejun Heo645a8d92007-11-27 09:30:39 +010093static inline struct page *sg_page(struct scatterlist *sg)
94{
95#ifdef CONFIG_DEBUG_SG
96 BUG_ON(sg->sg_magic != SG_MAGIC);
97 BUG_ON(sg_is_chain(sg));
98#endif
99 return (struct page *)((sg)->page_link & ~0x3);
100}
Jens Axboe82f66fb2007-10-22 17:07:37 +0200101
Jens Axboe18dabf42007-10-22 19:57:20 +0200102/**
103 * sg_set_buf - Set sg entry to point at given data
104 * @sg: SG entry
105 * @buf: Data
106 * @buflen: Data length
107 *
108 **/
Herbert Xu03fd9ce2006-08-14 23:11:53 +1000109static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
Herbert Xud32311f2005-09-17 14:41:40 +1000110 unsigned int buflen)
111{
Jens Axboe642f1492007-10-24 11:20:47 +0200112 sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113}
114
Jens Axboe96b418c2007-05-09 09:02:57 +0200115/*
116 * Loop over each sg element, following the pointer to a new list if necessary
117 */
118#define for_each_sg(sglist, sg, nr, __i) \
119 for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
120
Jens Axboe70eb8042007-07-16 21:17:16 +0200121/**
Jens Axboe70eb8042007-07-16 21:17:16 +0200122 * sg_chain - Chain two sglists together
123 * @prv: First scatterlist
124 * @prv_nents: Number of entries in prv
125 * @sgl: Second scatterlist
126 *
Jens Axboe18dabf42007-10-22 19:57:20 +0200127 * Description:
128 * Links @prv@ and @sgl@ together, to form a longer scatterlist.
Jens Axboe70eb8042007-07-16 21:17:16 +0200129 *
Jens Axboe18dabf42007-10-22 19:57:20 +0200130 **/
Jens Axboe70eb8042007-07-16 21:17:16 +0200131static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
132 struct scatterlist *sgl)
133{
134#ifndef ARCH_HAS_SG_CHAIN
135 BUG();
136#endif
Tejun Heo645a8d92007-11-27 09:30:39 +0100137
138 /*
139 * offset and length are unused for chain entry. Clear them.
140 */
Rusty Russellb801a1e2008-01-11 10:12:55 +0100141 prv[prv_nents - 1].offset = 0;
142 prv[prv_nents - 1].length = 0;
Tejun Heo645a8d92007-11-27 09:30:39 +0100143
Jens Axboe73fd5462007-10-26 09:32:16 +0200144 /*
145 * Set lowest bit to indicate a link pointer, and make sure to clear
146 * the termination bit if it happens to be set.
147 */
148 prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
Jens Axboe70eb8042007-07-16 21:17:16 +0200149}
150
Jens Axboe82f66fb2007-10-22 17:07:37 +0200151/**
152 * sg_mark_end - Mark the end of the scatterlist
Jens Axboec46f2332007-10-31 12:06:37 +0100153 * @sg: SG entryScatterlist
Jens Axboe82f66fb2007-10-22 17:07:37 +0200154 *
155 * Description:
Jens Axboec46f2332007-10-31 12:06:37 +0100156 * Marks the passed in sg entry as the termination point for the sg
157 * table. A call to sg_next() on this entry will return NULL.
Jens Axboe82f66fb2007-10-22 17:07:37 +0200158 *
159 **/
Jens Axboec46f2332007-10-31 12:06:37 +0100160static inline void sg_mark_end(struct scatterlist *sg)
Jens Axboe82f66fb2007-10-22 17:07:37 +0200161{
Jens Axboec46f2332007-10-31 12:06:37 +0100162#ifdef CONFIG_DEBUG_SG
163 BUG_ON(sg->sg_magic != SG_MAGIC);
164#endif
165 /*
166 * Set termination bit, clear potential chain bit
167 */
Jens Axboe18dabf42007-10-22 19:57:20 +0200168 sg->page_link |= 0x02;
Jens Axboec46f2332007-10-31 12:06:37 +0100169 sg->page_link &= ~0x01;
Jens Axboe82f66fb2007-10-22 17:07:37 +0200170}
171
Jens Axboe82f66fb2007-10-22 17:07:37 +0200172/**
Jens Axboe82f66fb2007-10-22 17:07:37 +0200173 * sg_phys - Return physical address of an sg entry
174 * @sg: SG entry
175 *
176 * Description:
177 * This calls page_to_phys() on the page in this sg entry, and adds the
178 * sg offset. The caller must know that it is legal to call page_to_phys()
179 * on the sg page.
180 *
181 **/
Hugh Dickins85cdffc2007-10-25 09:55:05 +0200182static inline dma_addr_t sg_phys(struct scatterlist *sg)
Jens Axboe82f66fb2007-10-22 17:07:37 +0200183{
184 return page_to_phys(sg_page(sg)) + sg->offset;
185}
186
187/**
188 * sg_virt - Return virtual address of an sg entry
Jens Axboe18dabf42007-10-22 19:57:20 +0200189 * @sg: SG entry
Jens Axboe82f66fb2007-10-22 17:07:37 +0200190 *
191 * Description:
192 * This calls page_address() on the page in this sg entry, and adds the
193 * sg offset. The caller must know that the sg page has a valid virtual
194 * mapping.
195 *
196 **/
197static inline void *sg_virt(struct scatterlist *sg)
198{
199 return page_address(sg_page(sg)) + sg->offset;
200}
201
Jens Axboe0db92992007-11-30 09:16:50 +0100202struct scatterlist *sg_next(struct scatterlist *);
203struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
204void sg_init_table(struct scatterlist *, unsigned int);
205void sg_init_one(struct scatterlist *, const void *, unsigned int);
206
207typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
208typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
209
James Bottomley7cedb1f2008-01-13 14:15:28 -0600210void __sg_free_table(struct sg_table *, unsigned int, sg_free_fn *);
Jens Axboe0db92992007-11-30 09:16:50 +0100211void sg_free_table(struct sg_table *);
James Bottomley7cedb1f2008-01-13 14:15:28 -0600212int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, gfp_t,
213 sg_alloc_fn *);
Jens Axboe0db92992007-11-30 09:16:50 +0100214int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
215
216/*
217 * Maximum number of entries that will be allocated in one piece, if
218 * a list larger than this is required then chaining will be utilized.
219 */
220#define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
221
Linus Torvalds1da177e2005-04-16 15:20:36 -0700222#endif /* _LINUX_SCATTERLIST_H */