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.
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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
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20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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30 #ifndef _LINUX_SCATTERLIST_H_
31 #define _LINUX_SCATTERLIST_H_
36 * If flags bit 0 is set, then the sg field contains a pointer to the next sg
37 * table list. Otherwise the next entry is at sg + 1, can be determined using
38 * the sg_is_chain() function.
40 * If flags bit 1 is set, then this sg entry is the last element in a list,
41 * can be determined using the sg_is_last() function.
50 struct scatterlist *sg;
59 struct scatterlist *sgl; /* the list */
60 unsigned int nents; /* number of mapped entries */
61 unsigned int orig_nents; /* original size of list */
65 * Maximum number of entries that will be allocated in one piece, if
66 * a list larger than this is required then chaining will be utilized.
68 #define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
70 #define sg_dma_address(sg) (sg)->address
71 #define sg_dma_len(sg) (sg)->length
72 #define sg_page(sg) (sg)->sl_un.page
73 #define sg_scatternext(sg) (sg)->sl_un.sg
79 sg_set_page(struct scatterlist *sg, struct vm_page *page, unsigned int len,
85 if (offset > PAGE_SIZE)
86 panic("sg_set_page: Invalid offset %d\n", offset);
91 sg_set_buf(struct scatterlist *sg, const void *buf, unsigned int buflen)
93 sg_set_page(sg, virt_to_page(buf), buflen,
94 ((uintptr_t)buf) & ~PAGE_MASK);
98 sg_init_table(struct scatterlist *sg, unsigned int nents)
100 bzero(sg, sizeof(*sg) * nents);
101 sg[nents - 1].flags = SG_END;
105 static inline struct scatterlist *
106 sg_next(struct scatterlist *sg)
108 if (sg->flags & SG_END)
111 if (sg->flags & SG_CHAIN)
112 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;
125 * sg_chain - Chain two sglists together
126 * @prv: First scatterlist
127 * @prv_nents: Number of entries in prv
128 * @sgl: Second scatterlist
131 * Links @prv@ and @sgl@ together, to form a longer scatterlist.
135 sg_chain(struct scatterlist *prv, unsigned int prv_nents,
136 struct scatterlist *sgl)
139 * offset and length are unused for chain entry. Clear them.
141 struct scatterlist *sg = &prv[prv_nents - 1];
147 * Indicate a link pointer, and set the link to the second list.
149 sg->flags = SG_CHAIN;
154 * sg_mark_end - Mark the end of the scatterlist
155 * @sg: SG entryScatterlist
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.
162 static inline void sg_mark_end(struct scatterlist *sg)
169 * __sg_free_table - Free a previously mapped sg table
170 * @table: The sg table header to use
171 * @max_ents: The maximum number of entries per single scatterlist
174 * Free an sg table previously allocated and setup with
175 * __sg_alloc_table(). The @max_ents value must be identical to
176 * that previously used with __sg_alloc_table().
180 __sg_free_table(struct sg_table *table, unsigned int max_ents)
182 struct scatterlist *sgl, *next;
184 if (unlikely(!table->sgl))
188 while (table->orig_nents) {
189 unsigned int alloc_size = table->orig_nents;
190 unsigned int sg_size;
193 * If we have more than max_ents segments left,
194 * then assign 'next' to the sg table after the current one.
195 * sg_size is then one less than alloc size, since the last
196 * element is the chain pointer.
198 if (alloc_size > max_ents) {
199 next = sgl[max_ents - 1].sl_un.sg;
200 alloc_size = max_ents;
201 sg_size = alloc_size - 1;
203 sg_size = alloc_size;
207 table->orig_nents -= sg_size;
216 * sg_free_table - Free a previously allocated sg table
217 * @table: The mapped sg table header
221 sg_free_table(struct sg_table *table)
223 __sg_free_table(table, SG_MAX_SINGLE_ALLOC);
227 * __sg_alloc_table - Allocate and initialize an sg table with given allocator
228 * @table: The sg table header to use
229 * @nents: Number of entries in sg list
230 * @max_ents: The maximum number of entries the allocator returns per call
231 * @gfp_mask: GFP allocation mask
234 * This function returns a @table @nents long. The allocator is
235 * defined to return scatterlist chunks of maximum size @max_ents.
236 * Thus if @nents is bigger than @max_ents, the scatterlists will be
237 * chained in units of @max_ents.
240 * If this function returns non-0 (eg failure), the caller must call
241 * __sg_free_table() to cleanup any leftover allocations.
245 __sg_alloc_table(struct sg_table *table, unsigned int nents,
246 unsigned int max_ents, gfp_t gfp_mask)
248 struct scatterlist *sg, *prv;
251 memset(table, 0, sizeof(*table));
258 unsigned int sg_size, alloc_size = left;
260 if (alloc_size > max_ents) {
261 alloc_size = max_ents;
262 sg_size = alloc_size - 1;
264 sg_size = alloc_size;
268 sg = kmalloc(alloc_size * sizeof(struct scatterlist), gfp_mask);
271 * Adjust entry count to reflect that the last
272 * entry of the previous table won't be used for
273 * linkage. Without this, sg_kfree() may get
277 table->nents = ++table->orig_nents;
282 sg_init_table(sg, alloc_size);
283 table->nents = table->orig_nents += sg_size;
286 * If this is the first mapping, assign the sg table header.
287 * If this is not the first mapping, chain previous part.
290 sg_chain(prv, max_ents, sg);
295 * If no more entries after this one, mark the end
298 sg_mark_end(&sg[sg_size - 1]);
307 * sg_alloc_table - Allocate and initialize an sg table
308 * @table: The sg table header to use
309 * @nents: Number of entries in sg list
310 * @gfp_mask: GFP allocation mask
313 * Allocate and initialize an sg table. If @nents@ is larger than
314 * SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
319 sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
323 ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
326 __sg_free_table(table, SG_MAX_SINGLE_ALLOC);
332 #define for_each_sg(sglist, sg, sgmax, _itr) \
333 for (_itr = 0, sg = (sglist); _itr < (sgmax); _itr++, sg = sg_next(sg))
335 #endif /* _LINUX_SCATTERLIST_H_ */