summaryrefslogtreecommitdiffstats
path: root/include/linux/scatterlist.h
blob: cb3c8fe6acd776f55f78ca9cebe05028b8c7cf70 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
#ifndef _LINUX_SCATTERLIST_H
#define _LINUX_SCATTERLIST_H

#include <linux/string.h>
#include <linux/types.h>
#include <linux/bug.h>
#include <linux/mm.h>
#include <asm/io.h>

struct scatterlist {
#ifdef CONFIG_DEBUG_SG
	unsigned long	sg_magic;
#endif
	unsigned long	page_link;
	unsigned int	offset;
	unsigned int	length;
	dma_addr_t	dma_address;
#ifdef CONFIG_NEED_SG_DMA_LENGTH
	unsigned int	dma_length;
#endif
};

/*
 * These macros should be used after a dma_map_sg call has been done
 * to get bus addresses of each of the SG entries and their lengths.
 * You should only work with the number of sg entries dma_map_sg
 * returns, or alternatively stop on the first sg_dma_len(sg) which
 * is 0.
 */
#define sg_dma_address(sg)	((sg)->dma_address)

#ifdef CONFIG_NEED_SG_DMA_LENGTH
#define sg_dma_len(sg)		((sg)->dma_length)
#else
#define sg_dma_len(sg)		((sg)->length)
#endif

struct sg_table {
	struct scatterlist *sgl;	/* the list */
	unsigned int nents;		/* number of mapped entries */
	unsigned int orig_nents;	/* original size of list */
};

/*
 * Notes on SG table design.
 *
 * We use the unsigned long page_link field in the scatterlist struct to place
 * the page pointer AND encode information about the sg table as well. The two
 * lower bits are reserved for this information.
 *
 * If bit 0 is set, then the page_link contains a pointer to the next sg
 * table list. Otherwise the next entry is at sg + 1.
 *
 * If bit 1 is set, then this sg entry is the last element in a list.
 *
 * See sg_next().
 *
 */

#define SG_MAGIC	0x87654321

/*
 * We overload the LSB of the page pointer to indicate whether it's
 * a valid sg entry, or whether it points to the start of a new scatterlist.
 * Those low bits are there for everyone! (thanks mason :-)
 */
#define sg_is_chain(sg)		((sg)->page_link & 0x01)
#define sg_is_last(sg)		((sg)->page_link & 0x02)
#define sg_chain_ptr(sg)	\
	((struct scatterlist *) ((sg)->page_link & ~0x03))

/**
 * sg_assign_page - Assign a given page to an SG entry
 * @sg:		    SG entry
 * @page:	    The page
 *
 * Description:
 *   Assign page to sg entry. Also see sg_set_page(), the most commonly used
 *   variant.
 *
 **/
static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
{
	unsigned long page_link = sg->page_link & 0x3;

	/*
	 * In order for the low bit stealing approach to work, pages
	 * must be aligned at a 32-bit boundary as a minimum.
	 */
	BUG_ON((unsigned long) page & 0x03);
#ifdef CONFIG_DEBUG_SG
	BUG_ON(sg->sg_magic != SG_MAGIC);
	BUG_ON(sg_is_chain(sg));
#endif
	sg->page_link = page_link | (unsigned long) page;
}

/**
 * sg_set_page - Set sg entry to point at given page
 * @sg:		 SG entry
 * @page:	 The page
 * @len:	 Length of data
 * @offset:	 Offset into page
 *
 * Description:
 *   Use this function to set an sg entry pointing at a page, never assign
 *   the page directly. We encode sg table information in the lower bits
 *   of the page pointer. See sg_page() for looking up the page belonging
 *   to an sg entry.
 *
 **/
static inline void sg_set_page(struct scatterlist *sg, struct page *page,
			       unsigned int len, unsigned int offset)
{
	sg_assign_page(sg, page);
	sg->offset = offset;
	sg->length = len;
}

static inline struct page *sg_page(struct scatterlist *sg)
{
#ifdef CONFIG_DEBUG_SG
	BUG_ON(sg->sg_magic != SG_MAGIC);
	BUG_ON(sg_is_chain(sg));
#endif
	return (struct page *)((sg)->page_link & ~0x3);
}

/**
 * sg_set_buf - Set sg entry to point at given data
 * @sg:		 SG entry
 * @buf:	 Data
 * @buflen:	 Data length
 *
 **/
static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
			      unsigned int buflen)
{
#ifdef CONFIG_DEBUG_SG
	BUG_ON(!virt_addr_valid(buf));
#endif
	sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
}

/*
 * Loop over each sg element, following the pointer to a new list if necessary
 */
#define for_each_sg(sglist, sg, nr, __i)	\
	for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))

/**
 * sg_chain - Chain two sglists together
 * @prv:	First scatterlist
 * @prv_nents:	Number of entries in prv
 * @sgl:	Second scatterlist
 *
 * Description:
 *   Links @prv@ and @sgl@ together, to form a longer scatterlist.
 *
 **/
static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
			    struct scatterlist *sgl)
{
	/*
	 * offset and length are unused for chain entry.  Clear them.
	 */
	prv[prv_nents - 1].offset = 0;
	prv[prv_nents - 1].length = 0;

	/*
	 * Set lowest bit to indicate a link pointer, and make sure to clear
	 * the termination bit if it happens to be set.
	 */
	prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
}

/**
 * sg_mark_end - Mark the end of the scatterlist
 * @sg:		 SG entryScatterlist
 *
 * Description:
 *   Marks the passed in sg entry as the termination point for the sg
 *   table. A call to sg_next() on this entry will return NULL.
 *
 **/
static inline void sg_mark_end(struct scatterlist *sg)
{
#ifdef CONFIG_DEBUG_SG
	BUG_ON(sg->sg_magic != SG_MAGIC);
#endif
	/*
	 * Set termination bit, clear potential chain bit
	 */
	sg->page_link |= 0x02;
	sg->page_link &= ~0x01;
}

/**
 * sg_unmark_end - Undo setting the end of the scatterlist
 * @sg:		 SG entryScatterlist
 *
 * Description:
 *   Removes the termination marker from the given entry of the scatterlist.
 *
 **/
static inline void sg_unmark_end(struct scatterlist *sg)
{
#ifdef CONFIG_DEBUG_SG
	BUG_ON(sg->sg_magic != SG_MAGIC);
#endif
	sg->page_link &= ~0x02;
}

/**
 * sg_phys - Return physical address of an sg entry
 * @sg:	     SG entry
 *
 * Description:
 *   This calls page_to_phys() on the page in this sg entry, and adds the
 *   sg offset. The caller must know that it is legal to call page_to_phys()
 *   on the sg page.
 *
 **/
static inline dma_addr_t sg_phys(struct scatterlist *sg)
{
	return page_to_phys(sg_page(sg)) + sg->offset;
}

/**
 * sg_virt - Return virtual address of an sg entry
 * @sg:      SG entry
 *
 * Description:
 *   This calls page_address() on the page in this sg entry, and adds the
 *   sg offset. The caller must know that the sg page has a valid virtual
 *   mapping.
 *
 **/
static inline void *sg_virt(struct scatterlist *sg)
{
	return page_address(sg_page(sg)) + sg->offset;
}

int sg_nents(struct scatterlist *sg);
int sg_nents_for_len(struct scatterlist *sg, u64 len);
struct scatterlist *sg_next(struct scatterlist *);
struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
void sg_init_table(struct scatterlist *, unsigned int);
void sg_init_one(struct scatterlist *, const void *, unsigned int);
int sg_split(struct scatterlist *in, const int in_mapped_nents,
	     const off_t skip, const int nb_splits,
	     const size_t *split_sizes,
	     struct scatterlist **out, int *out_mapped_nents,
	     gfp_t gfp_mask);

typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
typedef void (sg_free_fn)(struct scatterlist *, unsigned int);

void __sg_free_table(struct sg_table *, unsigned int, bool, sg_free_fn *);
void sg_free_table(struct sg_table *);
int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
		     struct scatterlist *, gfp_t, sg_alloc_fn *);
int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
int sg_alloc_table_from_pages(struct sg_table *sgt,
	struct page **pages, unsigned int n_pages,
	unsigned long offset, unsigned long size,
	gfp_t gfp_mask);

size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
		      size_t buflen, off_t skip, bool to_buffer);

size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
			   const void *buf, size_t buflen);
size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
			 void *buf, size_t buflen);

size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
			    const void *buf, size_t buflen, off_t skip);
size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
			  void *buf, size_t buflen, off_t skip);

/*
 * Maximum number of entries that will be allocated in one piece, if
 * a list larger than this is required then chaining will be utilized.
 */
#define SG_MAX_SINGLE_ALLOC		(PAGE_SIZE / sizeof(struct scatterlist))

/*
 * The maximum number of SG segments that we will put inside a
 * scatterlist (unless chaining is used). Should ideally fit inside a
 * single page, to avoid a higher order allocation.  We could define this
 * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order.  The
 * minimum value is 32
 */
#define SG_CHUNK_SIZE	128

/*
 * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
 * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
 */
#ifdef CONFIG_ARCH_HAS_SG_CHAIN
#define SG_MAX_SEGMENTS	2048
#else
#define SG_MAX_SEGMENTS	SG_CHUNK_SIZE
#endif

#ifdef CONFIG_SG_POOL
void sg_free_table_chained(struct sg_table *table, bool first_chunk);
int sg_alloc_table_chained(struct sg_table *table, int nents,
			   struct scatterlist *first_chunk);
#endif

/*
 * sg page iterator
 *
 * Iterates over sg entries page-by-page.  On each successful iteration,
 * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
 * to get the current page and its dma address. @piter->sg will point to the
 * sg holding this page and @piter->sg_pgoffset to the page's page offset
 * within the sg. The iteration will stop either when a maximum number of sg
 * entries was reached or a terminating sg (sg_last(sg) == true) was reached.
 */
struct sg_page_iter {
	struct scatterlist	*sg;		/* sg holding the page */
	unsigned int		sg_pgoffset;	/* page offset within the sg */

	/* these are internal states, keep away */
	unsigned int		__nents;	/* remaining sg entries */
	int			__pg_advance;	/* nr pages to advance at the
						 * next step */
};

bool __sg_page_iter_next(struct sg_page_iter *piter);
void __sg_page_iter_start(struct sg_page_iter *piter,
			  struct scatterlist *sglist, unsigned int nents,
			  unsigned long pgoffset);
/**
 * sg_page_iter_page - get the current page held by the page iterator
 * @piter:	page iterator holding the page
 */
static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
{
	return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
}

/**
 * sg_page_iter_dma_address - get the dma address of the current page held by
 * the page iterator.
 * @piter:	page iterator holding the page
 */
static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter)
{
	return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT);
}

/**
 * for_each_sg_page - iterate over the pages of the given sg list
 * @sglist:	sglist to iterate over
 * @piter:	page iterator to hold current page, sg, sg_pgoffset
 * @nents:	maximum number of sg entries to iterate over
 * @pgoffset:	starting page offset
 */
#define for_each_sg_page(sglist, piter, nents, pgoffset)		   \
	for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
	     __sg_page_iter_next(piter);)

/*
 * Mapping sg iterator
 *
 * Iterates over sg entries mapping page-by-page.  On each successful
 * iteration, @miter->page points to the mapped page and
 * @miter->length bytes of data can be accessed at @miter->addr.  As
 * long as an interation is enclosed between start and stop, the user
 * is free to choose control structure and when to stop.
 *
 * @miter->consumed is set to @miter->length on each iteration.  It
 * can be adjusted if the user can't consume all the bytes in one go.
 * Also, a stopped iteration can be resumed by calling next on it.
 * This is useful when iteration needs to release all resources and
 * continue later (e.g. at the next interrupt).
 */

#define SG_MITER_ATOMIC		(1 << 0)	 /* use kmap_atomic */
#define SG_MITER_TO_SG		(1 << 1)	/* flush back to phys on unmap */
#define SG_MITER_FROM_SG	(1 << 2)	/* nop */

struct sg_mapping_iter {
	/* the following three fields can be accessed directly */
	struct page		*page;		/* currently mapped page */
	void			*addr;		/* pointer to the mapped area */
	size_t			length;		/* length of the mapped area */
	size_t			consumed;	/* number of consumed bytes */
	struct sg_page_iter	piter;		/* page iterator */

	/* these are internal states, keep away */
	unsigned int		__offset;	/* offset within page */
	unsigned int		__remaining;	/* remaining bytes on page */
	unsigned int		__flags;
};

void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
		    unsigned int nents, unsigned int flags);
bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
bool sg_miter_next(struct sg_mapping_iter *miter);
void sg_miter_stop(struct sg_mapping_iter *miter);

#endif /* _LINUX_SCATTERLIST_H */
OpenPOWER on IntegriCloud