vchiq_util.c revision 302408 
1/**
2 * Copyright (c) 2010-2012 Broadcom. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions, and the following disclaimer,
9 *    without modification.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. The names of the above-listed copyright holders may not be used
14 *    to endorse or promote products derived from this software without
15 *    specific prior written permission.
16 *
17 * ALTERNATIVELY, this software may be distributed under the terms of the
18 * GNU General Public License ("GPL") version 2, as published by the Free
19 * Software Foundation.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
22 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
23 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
24 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
25 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
26 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
27 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
28 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
29 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
30 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
31 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32 */
33
34#include "vchiq_util.h"
35
36static inline int is_pow2(int i)
37{
38	return i && !(i & (i - 1));
39}
40
41int vchiu_queue_init(VCHIU_QUEUE_T *queue, int size)
42{
43	WARN_ON(!is_pow2(size));
44
45	queue->size = size;
46	queue->read = 0;
47	queue->write = 0;
48	queue->initialized = 1;
49
50	_sema_init(&queue->pop, 0);
51	_sema_init(&queue->push, 0);
52
53	queue->storage = kzalloc(size * sizeof(VCHIQ_HEADER_T *), GFP_KERNEL);
54	if (queue->storage == NULL) {
55		vchiu_queue_delete(queue);
56		return 0;
57	}
58	return 1;
59}
60
61void vchiu_queue_delete(VCHIU_QUEUE_T *queue)
62{
63	if (queue->storage != NULL)
64		kfree(queue->storage);
65}
66
67int vchiu_queue_is_empty(VCHIU_QUEUE_T *queue)
68{
69	return queue->read == queue->write;
70}
71
72int vchiu_queue_is_full(VCHIU_QUEUE_T *queue)
73{
74	return queue->write == queue->read + queue->size;
75}
76
77void vchiu_queue_push(VCHIU_QUEUE_T *queue, VCHIQ_HEADER_T *header)
78{
79	if (!queue->initialized)
80		return;
81
82	while (queue->write == queue->read + queue->size) {
83		if (down_interruptible(&queue->pop) != 0) {
84			flush_signals(current);
85		}
86	}
87
88	/*
89	 * Write to queue->storage must be visible after read from
90	 * queue->read
91	 */
92	smp_mb();
93
94	queue->storage[queue->write & (queue->size - 1)] = header;
95
96	/*
97	 * Write to queue->storage must be visible before write to
98	 * queue->write
99	 */
100	smp_wmb();
101
102	queue->write++;
103
104	up(&queue->push);
105}
106
107VCHIQ_HEADER_T *vchiu_queue_peek(VCHIU_QUEUE_T *queue)
108{
109	while (queue->write == queue->read) {
110		if (down_interruptible(&queue->push) != 0) {
111			flush_signals(current);
112		}
113	}
114
115	up(&queue->push); // We haven't removed anything from the queue.
116
117	/*
118	 * Read from queue->storage must be visible after read from
119	 * queue->write
120	 */
121	smp_rmb();
122
123	return queue->storage[queue->read & (queue->size - 1)];
124}
125
126VCHIQ_HEADER_T *vchiu_queue_pop(VCHIU_QUEUE_T *queue)
127{
128	VCHIQ_HEADER_T *header;
129
130	while (queue->write == queue->read) {
131		if (down_interruptible(&queue->push) != 0) {
132			flush_signals(current);
133		}
134	}
135
136	/*
137	 * Read from queue->storage must be visible after read from
138	 * queue->write
139	 */
140	smp_rmb();
141
142	header = queue->storage[queue->read & (queue->size - 1)];
143
144	/*
145	 * Read from queue->storage must be visible before write to
146	 * queue->read
147	 */
148	smp_mb();
149
150	queue->read++;
151
152	up(&queue->pop);
153
154	return header;
155}
156