1 /*
2 * Copyright (c) 2011 Chelsio Communications. All rights reserved.
3 *
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:
9 *
10 * Redistribution and use in source and binary forms, with or
11 * without modification, are permitted provided that the following
12 * conditions are met:
13 *
14 * - Redistributions of source code must retain the above
15 * copyright notice, this list of conditions and the following
16 * disclaimer.
17 *
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.
22 *
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
30 * SOFTWARE.
31 */
32 #include <linux/kernel.h>
33 #include <linux/random.h>
34 #include "iw_cxgb4.h"
35
36 #define RANDOM_SKIP 16
37
38 /*
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)
43 */
c4iw_id_alloc(struct c4iw_id_table * alloc)44 u32 c4iw_id_alloc(struct c4iw_id_table *alloc)
45 {
46 unsigned long flags;
47 u32 obj;
48
49 spin_lock_irqsave(&alloc->lock, flags);
50
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);
54
55 if (obj < alloc->max) {
56 if (alloc->flags & C4IW_ID_TABLE_F_RANDOM)
57 alloc->last += prandom_u32() % RANDOM_SKIP;
58 else
59 alloc->last = obj + 1;
60 if (alloc->last >= alloc->max)
61 alloc->last = 0;
62 __set_bit(obj, alloc->table);
63 obj += alloc->start;
64 } else
65 obj = -1;
66
67 spin_unlock_irqrestore(&alloc->lock, flags);
68 return obj;
69 }
70
c4iw_id_free(struct c4iw_id_table * alloc,u32 obj)71 void c4iw_id_free(struct c4iw_id_table *alloc, u32 obj)
72 {
73 unsigned long flags;
74
75 obj -= alloc->start;
76
77 spin_lock_irqsave(&alloc->lock, flags);
78 __clear_bit(obj, alloc->table);
79 spin_unlock_irqrestore(&alloc->lock, flags);
80 }
81
c4iw_id_table_alloc(struct c4iw_id_table * alloc,u32 start,u32 num,u32 reserved,u32 flags)82 int c4iw_id_table_alloc(struct c4iw_id_table *alloc, u32 start, u32 num,
83 u32 reserved, u32 flags)
84 {
85 alloc->start = start;
86 alloc->flags = flags;
87 if (flags & C4IW_ID_TABLE_F_RANDOM)
88 alloc->last = prandom_u32() % RANDOM_SKIP;
89 else
90 alloc->last = 0;
91 alloc->max = num;
92 spin_lock_init(&alloc->lock);
93 alloc->table = bitmap_zalloc(num, GFP_KERNEL);
94 if (!alloc->table)
95 return -ENOMEM;
96
97 if (!(alloc->flags & C4IW_ID_TABLE_F_EMPTY))
98 bitmap_set(alloc->table, 0, reserved);
99
100 return 0;
101 }
102
c4iw_id_table_free(struct c4iw_id_table * alloc)103 void c4iw_id_table_free(struct c4iw_id_table *alloc)
104 {
105 bitmap_free(alloc->table);
106 }
107