x86: relax RAM check in ioremap()
[wrt350n-kernel.git] / lib / scatterlist.c
blobacca4901046c45b055d98ff0b5858a3bc4056ff4
1 /*
2 * Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com>
4 * Scatterlist handling helpers.
6 * This source code is licensed under the GNU General Public License,
7 * Version 2. See the file COPYING for more details.
8 */
9 #include <linux/module.h>
10 #include <linux/scatterlist.h>
12 /**
13 * sg_next - return the next scatterlist entry in a list
14 * @sg: The current sg entry
16 * Description:
17 * Usually the next entry will be @sg@ + 1, but if this sg element is part
18 * of a chained scatterlist, it could jump to the start of a new
19 * scatterlist array.
21 **/
22 struct scatterlist *sg_next(struct scatterlist *sg)
24 #ifdef CONFIG_DEBUG_SG
25 BUG_ON(sg->sg_magic != SG_MAGIC);
26 #endif
27 if (sg_is_last(sg))
28 return NULL;
30 sg++;
31 if (unlikely(sg_is_chain(sg)))
32 sg = sg_chain_ptr(sg);
34 return sg;
36 EXPORT_SYMBOL(sg_next);
38 /**
39 * sg_last - return the last scatterlist entry in a list
40 * @sgl: First entry in the scatterlist
41 * @nents: Number of entries in the scatterlist
43 * Description:
44 * Should only be used casually, it (currently) scans the entire list
45 * to get the last entry.
47 * Note that the @sgl@ pointer passed in need not be the first one,
48 * the important bit is that @nents@ denotes the number of entries that
49 * exist from @sgl@.
51 **/
52 struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents)
54 #ifndef ARCH_HAS_SG_CHAIN
55 struct scatterlist *ret = &sgl[nents - 1];
56 #else
57 struct scatterlist *sg, *ret = NULL;
58 unsigned int i;
60 for_each_sg(sgl, sg, nents, i)
61 ret = sg;
63 #endif
64 #ifdef CONFIG_DEBUG_SG
65 BUG_ON(sgl[0].sg_magic != SG_MAGIC);
66 BUG_ON(!sg_is_last(ret));
67 #endif
68 return ret;
70 EXPORT_SYMBOL(sg_last);
72 /**
73 * sg_init_table - Initialize SG table
74 * @sgl: The SG table
75 * @nents: Number of entries in table
77 * Notes:
78 * If this is part of a chained sg table, sg_mark_end() should be
79 * used only on the last table part.
81 **/
82 void sg_init_table(struct scatterlist *sgl, unsigned int nents)
84 memset(sgl, 0, sizeof(*sgl) * nents);
85 #ifdef CONFIG_DEBUG_SG
87 unsigned int i;
88 for (i = 0; i < nents; i++)
89 sgl[i].sg_magic = SG_MAGIC;
91 #endif
92 sg_mark_end(&sgl[nents - 1]);
94 EXPORT_SYMBOL(sg_init_table);
96 /**
97 * sg_init_one - Initialize a single entry sg list
98 * @sg: SG entry
99 * @buf: Virtual address for IO
100 * @buflen: IO length
103 void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen)
105 sg_init_table(sg, 1);
106 sg_set_buf(sg, buf, buflen);
108 EXPORT_SYMBOL(sg_init_one);
111 * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
112 * helpers.
114 static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask)
116 if (nents == SG_MAX_SINGLE_ALLOC)
117 return (struct scatterlist *) __get_free_page(gfp_mask);
118 else
119 return kmalloc(nents * sizeof(struct scatterlist), gfp_mask);
122 static void sg_kfree(struct scatterlist *sg, unsigned int nents)
124 if (nents == SG_MAX_SINGLE_ALLOC)
125 free_page((unsigned long) sg);
126 else
127 kfree(sg);
131 * __sg_free_table - Free a previously mapped sg table
132 * @table: The sg table header to use
133 * @max_ents: The maximum number of entries per single scatterlist
134 * @free_fn: Free function
136 * Description:
137 * Free an sg table previously allocated and setup with
138 * __sg_alloc_table(). The @max_ents value must be identical to
139 * that previously used with __sg_alloc_table().
142 void __sg_free_table(struct sg_table *table, unsigned int max_ents,
143 sg_free_fn *free_fn)
145 struct scatterlist *sgl, *next;
147 if (unlikely(!table->sgl))
148 return;
150 sgl = table->sgl;
151 while (table->orig_nents) {
152 unsigned int alloc_size = table->orig_nents;
153 unsigned int sg_size;
156 * If we have more than max_ents segments left,
157 * then assign 'next' to the sg table after the current one.
158 * sg_size is then one less than alloc size, since the last
159 * element is the chain pointer.
161 if (alloc_size > max_ents) {
162 next = sg_chain_ptr(&sgl[max_ents - 1]);
163 alloc_size = max_ents;
164 sg_size = alloc_size - 1;
165 } else {
166 sg_size = alloc_size;
167 next = NULL;
170 table->orig_nents -= sg_size;
171 free_fn(sgl, alloc_size);
172 sgl = next;
175 table->sgl = NULL;
177 EXPORT_SYMBOL(__sg_free_table);
180 * sg_free_table - Free a previously allocated sg table
181 * @table: The mapped sg table header
184 void sg_free_table(struct sg_table *table)
186 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
188 EXPORT_SYMBOL(sg_free_table);
191 * __sg_alloc_table - Allocate and initialize an sg table with given allocator
192 * @table: The sg table header to use
193 * @nents: Number of entries in sg list
194 * @max_ents: The maximum number of entries the allocator returns per call
195 * @gfp_mask: GFP allocation mask
196 * @alloc_fn: Allocator to use
198 * Description:
199 * This function returns a @table @nents long. The allocator is
200 * defined to return scatterlist chunks of maximum size @max_ents.
201 * Thus if @nents is bigger than @max_ents, the scatterlists will be
202 * chained in units of @max_ents.
204 * Notes:
205 * If this function returns non-0 (eg failure), the caller must call
206 * __sg_free_table() to cleanup any leftover allocations.
209 int __sg_alloc_table(struct sg_table *table, unsigned int nents,
210 unsigned int max_ents, gfp_t gfp_mask,
211 sg_alloc_fn *alloc_fn)
213 struct scatterlist *sg, *prv;
214 unsigned int left;
216 #ifndef ARCH_HAS_SG_CHAIN
217 BUG_ON(nents > max_ents);
218 #endif
220 memset(table, 0, sizeof(*table));
222 left = nents;
223 prv = NULL;
224 do {
225 unsigned int sg_size, alloc_size = left;
227 if (alloc_size > max_ents) {
228 alloc_size = max_ents;
229 sg_size = alloc_size - 1;
230 } else
231 sg_size = alloc_size;
233 left -= sg_size;
235 sg = alloc_fn(alloc_size, gfp_mask);
236 if (unlikely(!sg))
237 return -ENOMEM;
239 sg_init_table(sg, alloc_size);
240 table->nents = table->orig_nents += sg_size;
243 * If this is the first mapping, assign the sg table header.
244 * If this is not the first mapping, chain previous part.
246 if (prv)
247 sg_chain(prv, max_ents, sg);
248 else
249 table->sgl = sg;
252 * If no more entries after this one, mark the end
254 if (!left)
255 sg_mark_end(&sg[sg_size - 1]);
258 * only really needed for mempool backed sg allocations (like
259 * SCSI), a possible improvement here would be to pass the
260 * table pointer into the allocator and let that clear these
261 * flags
263 gfp_mask &= ~__GFP_WAIT;
264 gfp_mask |= __GFP_HIGH;
265 prv = sg;
266 } while (left);
268 return 0;
270 EXPORT_SYMBOL(__sg_alloc_table);
273 * sg_alloc_table - Allocate and initialize an sg table
274 * @table: The sg table header to use
275 * @nents: Number of entries in sg list
276 * @gfp_mask: GFP allocation mask
278 * Description:
279 * Allocate and initialize an sg table. If @nents@ is larger than
280 * SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
283 int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
285 int ret;
287 ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
288 gfp_mask, sg_kmalloc);
289 if (unlikely(ret))
290 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
292 return ret;
294 EXPORT_SYMBOL(sg_alloc_table);