cam_semaphore.h revision 6f83d735d8e3b918da42e6b559fcd0efb78133e5 
1/* Copyright (c) 2012, The Linux Foundation. All rights reserved.
2 *
3 * Redistribution and use in source and binary forms, with or without
4 * modification, are permitted provided that the following conditions are
5 * met:
6 *     * Redistributions of source code must retain the above copyright
7 *       notice, this list of conditions and the following disclaimer.
8 *     * Redistributions in binary form must reproduce the above
9 *       copyright notice, this list of conditions and the following
10 *       disclaimer in the documentation and/or other materials provided
11 *       with the distribution.
12 *     * Neither the name of The Linux Foundation nor the names of its
13 *       contributors may be used to endorse or promote products derived
14 *       from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
17 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
18 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT
19 * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
23 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
24 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
25 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
26 * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 */
29
30#ifndef __QCAMERA_SEMAPHORE_H__
31#define __QCAMERA_SEMAPHORE_H__
32
33#ifdef __cplusplus
34extern "C" {
35#endif
36
37/* Implement semaphore with mutex and conditional variable.
38 * Reason being, POSIX semaphore on Android are not used or
39 * well tested.
40 */
41
42typedef struct {
43    int val;
44    pthread_mutex_t mutex;
45    pthread_cond_t cond;
46} cam_semaphore_t;
47
48static inline void cam_sem_init(cam_semaphore_t *s, int n)
49{
50    pthread_mutex_init(&(s->mutex), NULL);
51    pthread_cond_init(&(s->cond), NULL);
52    s->val = n;
53}
54
55static inline void cam_sem_post(cam_semaphore_t *s)
56{
57    pthread_mutex_lock(&(s->mutex));
58    s->val++;
59    pthread_cond_signal(&(s->cond));
60    pthread_mutex_unlock(&(s->mutex));
61}
62
63static inline int cam_sem_wait(cam_semaphore_t *s)
64{
65    int rc = 0;
66    pthread_mutex_lock(&(s->mutex));
67    while (s->val == 0)
68        rc = pthread_cond_wait(&(s->cond), &(s->mutex));
69    s->val--;
70    pthread_mutex_unlock(&(s->mutex));
71    return rc;
72}
73
74static inline void cam_sem_destroy(cam_semaphore_t *s)
75{
76    pthread_mutex_destroy(&(s->mutex));
77    pthread_cond_destroy(&(s->cond));
78    s->val = 0;
79}
80
81#ifdef __cplusplus
82}
83#endif
84
85#endif /* __QCAMERA_SEMAPHORE_H__ */
86