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