2 * Copyright (c) 2010 Isilon Systems, Inc.
3 * Copyright (c) 2010 iX Systems, Inc.
4 * Copyright (c) 2010 Panasas, Inc.
5 * Copyright (c) 2013, 2014 Mellanox Technologies, Ltd.
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice unmodified, this list of conditions, and the following
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 #ifndef _LINUX_SCATTERLIST_H_
31 #define _LINUX_SCATTERLIST_H_
33 #include <linux/page.h>
34 #include <linux/slab.h>
39 * If flags bit 0 is set, then the sg field contains a pointer to the next sg
40 * table list. Otherwise the next entry is at sg + 1, can be determined using
41 * the sg_is_chain() function.
43 * If flags bit 1 is set, then this sg entry is the last element in a list,
44 * can be determined using the sg_is_last() function.
53 struct scatterlist *sg;
62 struct scatterlist *sgl; /* the list */
63 unsigned int nents; /* number of mapped entries */
64 unsigned int orig_nents; /* original size of list */
68 * Maximum number of entries that will be allocated in one piece, if
69 * a list larger than this is required then chaining will be utilized.
71 #define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
73 #define sg_dma_address(sg) (sg)->address
74 #define sg_dma_len(sg) (sg)->length
75 #define sg_page(sg) (sg)->sl_un.page
76 #define sg_scatternext(sg) (sg)->sl_un.sg
82 sg_set_page(struct scatterlist *sg, struct page *page, unsigned int len,
88 if (offset > PAGE_SIZE)
89 panic("sg_set_page: Invalid offset %d\n", offset);
93 sg_set_buf(struct scatterlist *sg, const void *buf, unsigned int buflen)
95 sg_set_page(sg, virt_to_page(buf), buflen,
96 ((uintptr_t)buf) & ~PAGE_MASK);
100 sg_init_table(struct scatterlist *sg, unsigned int nents)
102 bzero(sg, sizeof(*sg) * nents);
103 sg[nents - 1].flags = SG_END;
106 static inline struct scatterlist *
107 sg_next(struct scatterlist *sg)
109 if (sg->flags & SG_END)
112 if (sg->flags & SG_CHAIN)
113 sg = sg_scatternext(sg);
117 static inline vm_paddr_t
118 sg_phys(struct scatterlist *sg)
120 return sg_page(sg)->phys_addr + sg->offset;
124 * sg_chain - Chain two sglists together
125 * @prv: First scatterlist
126 * @prv_nents: Number of entries in prv
127 * @sgl: Second scatterlist
130 * Links @prv@ and @sgl@ together, to form a longer scatterlist.
134 sg_chain(struct scatterlist *prv, unsigned int prv_nents,
135 struct scatterlist *sgl)
138 * offset and length are unused for chain entry. Clear them.
140 struct scatterlist *sg = &prv[prv_nents - 1];
146 * Indicate a link pointer, and set the link to the second list.
148 sg->flags = SG_CHAIN;
153 * sg_mark_end - Mark the end of the scatterlist
154 * @sg: SG entryScatterlist
157 * Marks the passed in sg entry as the termination point for the sg
158 * table. A call to sg_next() on this entry will return NULL.
161 static inline void sg_mark_end(struct scatterlist *sg)
167 * __sg_free_table - Free a previously mapped sg table
168 * @table: The sg table header to use
169 * @max_ents: The maximum number of entries per single scatterlist
172 * Free an sg table previously allocated and setup with
173 * __sg_alloc_table(). The @max_ents value must be identical to
174 * that previously used with __sg_alloc_table().
178 __sg_free_table(struct sg_table *table, unsigned int max_ents)
180 struct scatterlist *sgl, *next;
182 if (unlikely(!table->sgl))
186 while (table->orig_nents) {
187 unsigned int alloc_size = table->orig_nents;
188 unsigned int sg_size;
191 * If we have more than max_ents segments left,
192 * then assign 'next' to the sg table after the current one.
193 * sg_size is then one less than alloc size, since the last
194 * element is the chain pointer.
196 if (alloc_size > max_ents) {
197 next = sgl[max_ents - 1].sl_un.sg;
198 alloc_size = max_ents;
199 sg_size = alloc_size - 1;
201 sg_size = alloc_size;
205 table->orig_nents -= sg_size;
214 * sg_free_table - Free a previously allocated sg table
215 * @table: The mapped sg table header
219 sg_free_table(struct sg_table *table)
221 __sg_free_table(table, SG_MAX_SINGLE_ALLOC);
225 * __sg_alloc_table - Allocate and initialize an sg table with given allocator
226 * @table: The sg table header to use
227 * @nents: Number of entries in sg list
228 * @max_ents: The maximum number of entries the allocator returns per call
229 * @gfp_mask: GFP allocation mask
232 * This function returns a @table @nents long. The allocator is
233 * defined to return scatterlist chunks of maximum size @max_ents.
234 * Thus if @nents is bigger than @max_ents, the scatterlists will be
235 * chained in units of @max_ents.
238 * If this function returns non-0 (eg failure), the caller must call
239 * __sg_free_table() to cleanup any leftover allocations.
243 __sg_alloc_table(struct sg_table *table, unsigned int nents,
244 unsigned int max_ents, gfp_t gfp_mask)
246 struct scatterlist *sg, *prv;
249 memset(table, 0, sizeof(*table));
256 unsigned int sg_size, alloc_size = left;
258 if (alloc_size > max_ents) {
259 alloc_size = max_ents;
260 sg_size = alloc_size - 1;
262 sg_size = alloc_size;
266 sg = kmalloc(alloc_size * sizeof(struct scatterlist), gfp_mask);
269 * Adjust entry count to reflect that the last
270 * entry of the previous table won't be used for
271 * linkage. Without this, sg_kfree() may get
275 table->nents = ++table->orig_nents;
280 sg_init_table(sg, alloc_size);
281 table->nents = table->orig_nents += sg_size;
284 * If this is the first mapping, assign the sg table header.
285 * If this is not the first mapping, chain previous part.
288 sg_chain(prv, max_ents, sg);
293 * If no more entries after this one, mark the end
296 sg_mark_end(&sg[sg_size - 1]);
305 * sg_alloc_table - Allocate and initialize an sg table
306 * @table: The sg table header to use
307 * @nents: Number of entries in sg list
308 * @gfp_mask: GFP allocation mask
311 * Allocate and initialize an sg table. If @nents@ is larger than
312 * SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
317 sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
321 ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
324 __sg_free_table(table, SG_MAX_SINGLE_ALLOC);
329 #define for_each_sg(sglist, sg, sgmax, _itr) \
330 for (_itr = 0, sg = (sglist); _itr < (sgmax); _itr++, sg = sg_next(sg))
332 #endif /* _LINUX_SCATTERLIST_H_ */