2 * Copyright (c) 2011 Chelsio Communications. All rights reserved.
4 * This software is available to you under a choice of one of two
5 * licenses. You may choose to be licensed under the terms of the GNU
6 * General Public License (GPL) Version 2, available from the file
7 * COPYING in the main directory of this source tree, or the
8 * OpenIB.org BSD license below:
10 * Redistribution and use in source and binary forms, with or
11 * without modification, are permitted provided that the following
14 * - Redistributions of source code must retain the above
15 * copyright notice, this list of conditions and the following
18 * - Redistributions in binary form must reproduce the above
19 * copyright notice, this list of conditions and the following
20 * disclaimer in the documentation and/or other materials
21 * provided with the distribution.
23 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
24 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
25 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
26 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
27 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
28 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
29 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
32 #include <linux/kernel.h>
33 #include <linux/random.h>
36 #define RANDOM_SKIP 16
39 * Trivial bitmap-based allocator. If the random flag is set, the
40 * allocator is designed to:
41 * - pseudo-randomize the id returned such that it is not trivially predictable.
42 * - avoid reuse of recently used id (at the expense of predictability)
44 u32 c4iw_id_alloc(struct c4iw_id_table *alloc)
49 spin_lock_irqsave(&alloc->lock, flags);
51 obj = find_next_zero_bit(alloc->table, alloc->max, alloc->last);
52 if (obj >= alloc->max)
53 obj = find_first_zero_bit(alloc->table, alloc->max);
55 if (obj < alloc->max) {
56 if (alloc->flags & C4IW_ID_TABLE_F_RANDOM)
57 alloc->last += prandom_u32() % RANDOM_SKIP;
59 alloc->last = obj + 1;
60 if (alloc->last >= alloc->max)
62 set_bit(obj, alloc->table);
67 spin_unlock_irqrestore(&alloc->lock, flags);
71 void c4iw_id_free(struct c4iw_id_table *alloc, u32 obj)
78 spin_lock_irqsave(&alloc->lock, flags);
79 clear_bit(obj, alloc->table);
80 spin_unlock_irqrestore(&alloc->lock, flags);
83 int c4iw_id_table_alloc(struct c4iw_id_table *alloc, u32 start, u32 num,
84 u32 reserved, u32 flags)
90 if (flags & C4IW_ID_TABLE_F_RANDOM)
91 alloc->last = prandom_u32() % RANDOM_SKIP;
95 spin_lock_init(&alloc->lock);
96 alloc->table = kmalloc(BITS_TO_LONGS(num) * sizeof(long),
101 bitmap_zero(alloc->table, num);
102 if (!(alloc->flags & C4IW_ID_TABLE_F_EMPTY))
103 for (i = 0; i < reserved; ++i)
104 set_bit(i, alloc->table);
109 void c4iw_id_table_free(struct c4iw_id_table *alloc)