1 /*
2 * Copyright (c) 2012-2016 VMware, Inc. All rights reserved.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of EITHER the GNU General Public License
6 * version 2 as published by the Free Software Foundation or the BSD
7 * 2-Clause License. This program is distributed in the hope that it
8 * will be useful, but WITHOUT ANY WARRANTY; WITHOUT EVEN THE IMPLIED
9 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
10 * See the GNU General Public License version 2 for more details at
11 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html.
12 *
13 * You should have received a copy of the GNU General Public License
14 * along with this program available in the file COPYING in the main
15 * directory of this source tree.
16 *
17 * The BSD 2-Clause License
18 *
19 * Redistribution and use in source and binary forms, with or
20 * without modification, are permitted provided that the following
21 * conditions are met:
22 *
23 * - Redistributions of source code must retain the above
24 * copyright notice, this list of conditions and the following
25 * disclaimer.
26 *
27 * - Redistributions in binary form must reproduce the above
28 * copyright notice, this list of conditions and the following
29 * disclaimer in the documentation and/or other materials
30 * provided with the distribution.
31 *
32 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
33 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
34 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
35 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
36 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
37 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
38 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
39 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
40 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
41 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
42 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
43 * OF THE POSSIBILITY OF SUCH DAMAGE.
44 */
45
46 #ifndef __PVRDMA_RING_H__
47 #define __PVRDMA_RING_H__
48
49 #include <linux/types.h>
50
51 #define PVRDMA_INVALID_IDX -1 /* Invalid index. */
52
53 struct pvrdma_ring {
54 atomic_t prod_tail; /* Producer tail. */
55 atomic_t cons_head; /* Consumer head. */
56 };
57
58 struct pvrdma_ring_state {
59 struct pvrdma_ring tx; /* Tx ring. */
60 struct pvrdma_ring rx; /* Rx ring. */
61 };
62
63 static inline int pvrdma_idx_valid(__u32 idx, __u32 max_elems)
64 {
65 /* Generates fewer instructions than a less-than. */
66 return (idx & ~((max_elems << 1) - 1)) == 0;
67 }
68
69 static inline __s32 pvrdma_idx(atomic_t *var, __u32 max_elems)
70 {
71 const unsigned int idx = atomic_read(var);
72
73 if (pvrdma_idx_valid(idx, max_elems))
74 return idx & (max_elems - 1);
75 return PVRDMA_INVALID_IDX;
76 }
77
78 static inline void pvrdma_idx_ring_inc(atomic_t *var, __u32 max_elems)
79 {
80 __u32 idx = atomic_read(var) + 1; /* Increment. */
81
82 idx &= (max_elems << 1) - 1; /* Modulo size, flip gen. */
83 atomic_set(var, idx);
84 }
85
86 static inline __s32 pvrdma_idx_ring_has_space(const struct pvrdma_ring *r,
87 __u32 max_elems, __u32 *out_tail)
88 {
89 const __u32 tail = atomic_read(&r->prod_tail);
90 const __u32 head = atomic_read(&r->cons_head);
91
92 if (pvrdma_idx_valid(tail, max_elems) &&
93 pvrdma_idx_valid(head, max_elems)) {
94 *out_tail = tail & (max_elems - 1);
95 return tail != (head ^ max_elems);
96 }
97 return PVRDMA_INVALID_IDX;
98 }
99
100 static inline __s32 pvrdma_idx_ring_has_data(const struct pvrdma_ring *r,
101 __u32 max_elems, __u32 *out_head)
102 {
103 const __u32 tail = atomic_read(&r->prod_tail);
104 const __u32 head = atomic_read(&r->cons_head);
105
106 if (pvrdma_idx_valid(tail, max_elems) &&
107 pvrdma_idx_valid(head, max_elems)) {
108 *out_head = head & (max_elems - 1);
109 return tail != head;
110 }
111 return PVRDMA_INVALID_IDX;
112 }
113
114 #endif /* __PVRDMA_RING_H__ */