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#ifdef CONFIG_DEBUG_SG
115	BUG_ON(!virt_addr_valid(buf));
116#endif
117	sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
118}
119
120/*
121 * Loop over each sg element, following the pointer to a new list if necessary
122 */
123#define for_each_sg(sglist, sg, nr, __i)	\
124	for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
125
126/**
127 * sg_chain - Chain two sglists together
128 * @prv:	First scatterlist
129 * @prv_nents:	Number of entries in prv
130 * @sgl:	Second scatterlist
131 *
132 * Description:
133 *   Links @prv@ and @sgl@ together, to form a longer scatterlist.
134 *
135 **/
136static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
137			    struct scatterlist *sgl)
138{
139#ifndef CONFIG_ARCH_HAS_SG_CHAIN
140	BUG();
141#endif
142
143	/*
144	 * offset and length are unused for chain entry.  Clear them.
145	 */
146	prv[prv_nents - 1].offset = 0;
147	prv[prv_nents - 1].length = 0;
148
149	/*
150	 * Set lowest bit to indicate a link pointer, and make sure to clear
151	 * the termination bit if it happens to be set.
152	 */
153	prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
154}
155
156/**
157 * sg_mark_end - Mark the end of the scatterlist
158 * @sg:		 SG entryScatterlist
159 *
160 * Description:
161 *   Marks the passed in sg entry as the termination point for the sg
162 *   table. A call to sg_next() on this entry will return NULL.
163 *
164 **/
165static inline void sg_mark_end(struct scatterlist *sg)
166{
167#ifdef CONFIG_DEBUG_SG
168	BUG_ON(sg->sg_magic != SG_MAGIC);
169#endif
170	/*
171	 * Set termination bit, clear potential chain bit
172	 */
173	sg->page_link |= 0x02;
174	sg->page_link &= ~0x01;
175}
176
177/**
178 * sg_unmark_end - Undo setting the end of the scatterlist
179 * @sg:		 SG entryScatterlist
180 *
181 * Description:
182 *   Removes the termination marker from the given entry of the scatterlist.
183 *
184 **/
185static inline void sg_unmark_end(struct scatterlist *sg)
186{
187#ifdef CONFIG_DEBUG_SG
188	BUG_ON(sg->sg_magic != SG_MAGIC);
189#endif
190	sg->page_link &= ~0x02;
191}
192
193/**
194 * sg_phys - Return physical address of an sg entry
195 * @sg:	     SG entry
196 *
197 * Description:
198 *   This calls page_to_phys() on the page in this sg entry, and adds the
199 *   sg offset. The caller must know that it is legal to call page_to_phys()
200 *   on the sg page.
201 *
202 **/
203static inline dma_addr_t sg_phys(struct scatterlist *sg)
204{
205	return page_to_phys(sg_page(sg)) + sg->offset;
206}
207
208/**
209 * sg_virt - Return virtual address of an sg entry
210 * @sg:      SG entry
211 *
212 * Description:
213 *   This calls page_address() on the page in this sg entry, and adds the
214 *   sg offset. The caller must know that the sg page has a valid virtual
215 *   mapping.
216 *
217 **/
218static inline void *sg_virt(struct scatterlist *sg)
219{
220	return page_address(sg_page(sg)) + sg->offset;
221}
222
223int sg_nents(struct scatterlist *sg);
224struct scatterlist *sg_next(struct scatterlist *);
225struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
226void sg_init_table(struct scatterlist *, unsigned int);
227void sg_init_one(struct scatterlist *, const void *, unsigned int);
228
229typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
230typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
231
232void __sg_free_table(struct sg_table *, unsigned int, bool, sg_free_fn *);
233void sg_free_table(struct sg_table *);
234int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
235		     struct scatterlist *, gfp_t, sg_alloc_fn *);
236int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
237int sg_alloc_table_from_pages(struct sg_table *sgt,
238	struct page **pages, unsigned int n_pages,
239	unsigned long offset, unsigned long size,
240	gfp_t gfp_mask);
241
242size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
243			   void *buf, size_t buflen);
244size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
245			 void *buf, size_t buflen);
246
247size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
248			    void *buf, size_t buflen, off_t skip);
249size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
250			  void *buf, size_t buflen, off_t skip);
251
252/*
253 * Maximum number of entries that will be allocated in one piece, if
254 * a list larger than this is required then chaining will be utilized.
255 */
256#define SG_MAX_SINGLE_ALLOC		(PAGE_SIZE / sizeof(struct scatterlist))
257
258/*
259 * sg page iterator
260 *
261 * Iterates over sg entries page-by-page.  On each successful iteration,
262 * you can call sg_page_iter_page(@piter) and sg_page_iter_dma_address(@piter)
263 * to get the current page and its dma address. @piter->sg will point to the
264 * sg holding this page and @piter->sg_pgoffset to the page's page offset
265 * within the sg. The iteration will stop either when a maximum number of sg
266 * entries was reached or a terminating sg (sg_last(sg) == true) was reached.
267 */
268struct sg_page_iter {
269	struct scatterlist	*sg;		/* sg holding the page */
270	unsigned int		sg_pgoffset;	/* page offset within the sg */
271
272	/* these are internal states, keep away */
273	unsigned int		__nents;	/* remaining sg entries */
274	int			__pg_advance;	/* nr pages to advance at the
275						 * next step */
276};
277
278bool __sg_page_iter_next(struct sg_page_iter *piter);
279void __sg_page_iter_start(struct sg_page_iter *piter,
280			  struct scatterlist *sglist, unsigned int nents,
281			  unsigned long pgoffset);
282/**
283 * sg_page_iter_page - get the current page held by the page iterator
284 * @piter:	page iterator holding the page
285 */
286static inline struct page *sg_page_iter_page(struct sg_page_iter *piter)
287{
288	return nth_page(sg_page(piter->sg), piter->sg_pgoffset);
289}
290
291/**
292 * sg_page_iter_dma_address - get the dma address of the current page held by
293 * the page iterator.
294 * @piter:	page iterator holding the page
295 */
296static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter)
297{
298	return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT);
299}
300
301/**
302 * for_each_sg_page - iterate over the pages of the given sg list
303 * @sglist:	sglist to iterate over
304 * @piter:	page iterator to hold current page, sg, sg_pgoffset
305 * @nents:	maximum number of sg entries to iterate over
306 * @pgoffset:	starting page offset
307 */
308#define for_each_sg_page(sglist, piter, nents, pgoffset)		   \
309	for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
310	     __sg_page_iter_next(piter);)
311
312/*
313 * Mapping sg iterator
314 *
315 * Iterates over sg entries mapping page-by-page.  On each successful
316 * iteration, @miter->page points to the mapped page and
317 * @miter->length bytes of data can be accessed at @miter->addr.  As
318 * long as an interation is enclosed between start and stop, the user
319 * is free to choose control structure and when to stop.
320 *
321 * @miter->consumed is set to @miter->length on each iteration.  It
322 * can be adjusted if the user can't consume all the bytes in one go.
323 * Also, a stopped iteration can be resumed by calling next on it.
324 * This is useful when iteration needs to release all resources and
325 * continue later (e.g. at the next interrupt).
326 */
327
328#define SG_MITER_ATOMIC		(1 << 0)	 /* use kmap_atomic */
329#define SG_MITER_TO_SG		(1 << 1)	/* flush back to phys on unmap */
330#define SG_MITER_FROM_SG	(1 << 2)	/* nop */
331
332struct sg_mapping_iter {
333	/* the following three fields can be accessed directly */
334	struct page		*page;		/* currently mapped page */
335	void			*addr;		/* pointer to the mapped area */
336	size_t			length;		/* length of the mapped area */
337	size_t			consumed;	/* number of consumed bytes */
338	struct sg_page_iter	piter;		/* page iterator */
339
340	/* these are internal states, keep away */
341	unsigned int		__offset;	/* offset within page */
342	unsigned int		__remaining;	/* remaining bytes on page */
343	unsigned int		__flags;
344};
345
346void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
347		    unsigned int nents, unsigned int flags);
348bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset);
349bool sg_miter_next(struct sg_mapping_iter *miter);
350void sg_miter_stop(struct sg_mapping_iter *miter);
351
352#endif /* _LINUX_SCATTERLIST_H */
353