xref: /freebsd/sys/dev/cxgbe/iw_cxgbe/id_table.c (revision 5ca8e32633c4ffbbcd6762e5888b6a4ba0708c6c)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause
3  *
4  * Copyright (c) 2011-2013 Chelsio Communications.  All rights reserved.
5  *
6  * This software is available to you under a choice of one of two
7  * licenses.  You may choose to be licensed under the terms of the GNU
8  * General Public License (GPL) Version 2, available from the file
9  * COPYING in the main directory of this source tree, or the
10  * OpenIB.org BSD license below:
11  *
12  *     Redistribution and use in source and binary forms, with or
13  *     without modification, are permitted provided that the following
14  *     conditions are met:
15  *
16  *      - Redistributions of source code must retain the above
17  *        copyright notice, this list of conditions and the following
18  *        disclaimer.
19  *
20  *      - Redistributions in binary form must reproduce the above
21  *        copyright notice, this list of conditions and the following
22  *        disclaimer in the documentation and/or other materials
23  *        provided with the distribution.
24  *
25  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
26  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
27  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
28  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
29  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
30  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
31  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
32  * SOFTWARE.
33  */
34 #include <sys/cdefs.h>
35 #include "opt_inet.h"
36 
37 #ifdef TCP_OFFLOAD
38 #include <sys/libkern.h>
39 #include "iw_cxgbe.h"
40 
41 #define RANDOM_SKIP 16
42 
43 /*
44  * Trivial bitmap-based allocator. If the random flag is set, the
45  * allocator is designed to:
46  * - pseudo-randomize the id returned such that it is not trivially predictable.
47  * - avoid reuse of recently used id (at the expense of predictability)
48  */
49 u32 c4iw_id_alloc(struct c4iw_id_table *alloc)
50 {
51 	unsigned long flags;
52 	u32 obj;
53 
54 	spin_lock_irqsave(&alloc->lock, flags);
55 
56 	obj = find_next_zero_bit(alloc->table, alloc->max, alloc->last);
57 	if (obj >= alloc->max)
58 		obj = find_first_zero_bit(alloc->table, alloc->max);
59 
60 	if (obj < alloc->max) {
61 		if (alloc->flags & C4IW_ID_TABLE_F_RANDOM)
62 			alloc->last += arc4random() % RANDOM_SKIP;
63 		else
64 			alloc->last = obj + 1;
65 		if (alloc->last >= alloc->max)
66 			alloc->last = 0;
67 		set_bit(obj, alloc->table);
68 		obj += alloc->start;
69 	} else
70 		obj = -1;
71 
72 	spin_unlock_irqrestore(&alloc->lock, flags);
73 	return obj;
74 }
75 
76 void c4iw_id_free(struct c4iw_id_table *alloc, u32 obj)
77 {
78 	unsigned long flags;
79 
80 	obj -= alloc->start;
81 	BUG_ON((int)obj < 0);
82 
83 	spin_lock_irqsave(&alloc->lock, flags);
84 	clear_bit(obj, alloc->table);
85 	spin_unlock_irqrestore(&alloc->lock, flags);
86 }
87 
88 int c4iw_id_table_alloc(struct c4iw_id_table *alloc, u32 start, u32 num,
89 			u32 reserved, u32 flags)
90 {
91 	int i;
92 
93 	alloc->start = start;
94 	alloc->flags = flags;
95 	if (flags & C4IW_ID_TABLE_F_RANDOM)
96 		alloc->last = arc4random() % RANDOM_SKIP;
97 	else
98 		alloc->last = 0;
99 	alloc->max  = num;
100 	spin_lock_init(&alloc->lock);
101 	alloc->table = kmalloc(BITS_TO_LONGS(num) * sizeof(long),
102 				GFP_KERNEL);
103 	if (!alloc->table)
104 		return -ENOMEM;
105 
106 	bitmap_zero(alloc->table, num);
107 	if (!(alloc->flags & C4IW_ID_TABLE_F_EMPTY))
108 		for (i = 0; i < reserved; ++i)
109 			set_bit(i, alloc->table);
110 
111 	return 0;
112 }
113 
114 void c4iw_id_table_free(struct c4iw_id_table *alloc)
115 {
116 	kfree(alloc->table);
117 }
118 #endif
119