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
53struct pvrdma_ring {
54	atomic_t prod_tail;	/* Producer tail. */
55	atomic_t cons_head;	/* Consumer head. */
56};
57
58struct pvrdma_ring_state {
59	struct pvrdma_ring tx;	/* Tx ring. */
60	struct pvrdma_ring rx;	/* Rx ring. */
61};
62
63static 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
69static 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
78static 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
86static 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
100static 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__ */
115