vchiq_util.c revision 278277 
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
49	_sema_init(&queue->pop, 0);
50	_sema_init(&queue->push, 0);
51
52	queue->storage = kzalloc(size * sizeof(VCHIQ_HEADER_T *), GFP_KERNEL);
53	if (queue->storage == NULL) {
54		vchiu_queue_delete(queue);
55		return 0;
56	}
57	return 1;
58}
59
60void vchiu_queue_delete(VCHIU_QUEUE_T *queue)
61{
62	if (queue->storage != NULL)
63		kfree(queue->storage);
64}
65
66int vchiu_queue_is_empty(VCHIU_QUEUE_T *queue)
67{
68	return queue->read == queue->write;
69}
70
71int vchiu_queue_is_full(VCHIU_QUEUE_T *queue)
72{
73	return queue->write == queue->read + queue->size;
74}
75
76void vchiu_queue_push(VCHIU_QUEUE_T *queue, VCHIQ_HEADER_T *header)
77{
78	while (queue->write == queue->read + queue->size) {
79		if (down_interruptible(&queue->pop) != 0) {
80			flush_signals(current);
81		}
82	}
83
84	/*
85	 * Write to queue->storage must be visible after read from
86	 * queue->read
87	 */
88	smp_mb();
89
90	queue->storage[queue->write & (queue->size - 1)] = header;
91
92	/*
93	 * Write to queue->storage must be visible before write to
94	 * queue->write
95	 */
96	smp_wmb();
97
98	queue->write++;
99
100	up(&queue->push);
101}
102
103VCHIQ_HEADER_T *vchiu_queue_peek(VCHIU_QUEUE_T *queue)
104{
105	while (queue->write == queue->read) {
106		if (down_interruptible(&queue->push) != 0) {
107			flush_signals(current);
108		}
109	}
110
111	up(&queue->push); // We haven't removed anything from the queue.
112
113	/*
114	 * Read from queue->storage must be visible after read from
115	 * queue->write
116	 */
117	smp_rmb();
118
119	return queue->storage[queue->read & (queue->size - 1)];
120}
121
122VCHIQ_HEADER_T *vchiu_queue_pop(VCHIU_QUEUE_T *queue)
123{
124	VCHIQ_HEADER_T *header;
125
126	while (queue->write == queue->read) {
127		if (down_interruptible(&queue->push) != 0) {
128			flush_signals(current);
129		}
130	}
131
132	/*
133	 * Read from queue->storage must be visible after read from
134	 * queue->write
135	 */
136	smp_rmb();
137
138	header = queue->storage[queue->read & (queue->size - 1)];
139
140	/*
141	 * Read from queue->storage must be visible before write to
142	 * queue->read
143	 */
144	smp_mb();
145
146	queue->read++;
147
148	up(&queue->pop);
149
150	return header;
151}
152