ALSA: pcm: fix delta calculation at boundary wraparound
[linux-2.6.git] / sound / core / hrtimer.c
1 /*
2  * ALSA timer back-end using hrtimer
3  * Copyright (C) 2008 Takashi Iwai
4  *
5  *   This program is free software; you can redistribute it and/or modify
6  *   it under the terms of the GNU General Public License as published by
7  *   the Free Software Foundation; either version 2 of the License, or
8  *   (at your option) any later version.
9  *
10  *   This program is distributed in the hope that it will be useful,
11  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
12  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  *   GNU General Public License for more details.
14  *
15  *   You should have received a copy of the GNU General Public License
16  *   along with this program; if not, write to the Free Software
17  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
18  *
19  */
20
21 #include <linux/init.h>
22 #include <linux/slab.h>
23 #include <linux/module.h>
24 #include <linux/moduleparam.h>
25 #include <linux/hrtimer.h>
26 #include <sound/core.h>
27 #include <sound/timer.h>
28
29 MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
30 MODULE_DESCRIPTION("ALSA hrtimer backend");
31 MODULE_LICENSE("GPL");
32
33 MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER));
34
35 #define NANO_SEC        1000000000UL    /* 10^9 in sec */
36 static unsigned int resolution;
37
38 struct snd_hrtimer {
39         struct snd_timer *timer;
40         struct hrtimer hrt;
41         atomic_t running;
42 };
43
44 static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt)
45 {
46         struct snd_hrtimer *stime = container_of(hrt, struct snd_hrtimer, hrt);
47         struct snd_timer *t = stime->timer;
48
49         if (!atomic_read(&stime->running))
50                 return HRTIMER_NORESTART;
51
52         hrtimer_forward_now(hrt, ns_to_ktime(t->sticks * resolution));
53         snd_timer_interrupt(stime->timer, t->sticks);
54
55         if (!atomic_read(&stime->running))
56                 return HRTIMER_NORESTART;
57         return HRTIMER_RESTART;
58 }
59
60 static int snd_hrtimer_open(struct snd_timer *t)
61 {
62         struct snd_hrtimer *stime;
63
64         stime = kmalloc(sizeof(*stime), GFP_KERNEL);
65         if (!stime)
66                 return -ENOMEM;
67         hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
68         stime->timer = t;
69         stime->hrt.function = snd_hrtimer_callback;
70         atomic_set(&stime->running, 0);
71         t->private_data = stime;
72         return 0;
73 }
74
75 static int snd_hrtimer_close(struct snd_timer *t)
76 {
77         struct snd_hrtimer *stime = t->private_data;
78
79         if (stime) {
80                 hrtimer_cancel(&stime->hrt);
81                 kfree(stime);
82                 t->private_data = NULL;
83         }
84         return 0;
85 }
86
87 static int snd_hrtimer_start(struct snd_timer *t)
88 {
89         struct snd_hrtimer *stime = t->private_data;
90
91         atomic_set(&stime->running, 0);
92         hrtimer_cancel(&stime->hrt);
93         hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution),
94                       HRTIMER_MODE_REL);
95         atomic_set(&stime->running, 1);
96         return 0;
97 }
98
99 static int snd_hrtimer_stop(struct snd_timer *t)
100 {
101         struct snd_hrtimer *stime = t->private_data;
102         atomic_set(&stime->running, 0);
103         return 0;
104 }
105
106 static struct snd_timer_hardware hrtimer_hw = {
107         .flags =        SNDRV_TIMER_HW_AUTO,
108         .open =         snd_hrtimer_open,
109         .close =        snd_hrtimer_close,
110         .start =        snd_hrtimer_start,
111         .stop =         snd_hrtimer_stop,
112 };
113
114 /*
115  * entry functions
116  */
117
118 static struct snd_timer *mytimer;
119
120 static int __init snd_hrtimer_init(void)
121 {
122         struct snd_timer *timer;
123         struct timespec tp;
124         int err;
125
126         hrtimer_get_res(CLOCK_MONOTONIC, &tp);
127         if (tp.tv_sec > 0 || !tp.tv_nsec) {
128                 snd_printk(KERN_ERR
129                            "snd-hrtimer: Invalid resolution %u.%09u",
130                            (unsigned)tp.tv_sec, (unsigned)tp.tv_nsec);
131                 return -EINVAL;
132         }
133         resolution = tp.tv_nsec;
134
135         /* Create a new timer and set up the fields */
136         err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER,
137                                    &timer);
138         if (err < 0)
139                 return err;
140
141         timer->module = THIS_MODULE;
142         strcpy(timer->name, "HR timer");
143         timer->hw = hrtimer_hw;
144         timer->hw.resolution = resolution;
145         timer->hw.ticks = NANO_SEC / resolution;
146
147         err = snd_timer_global_register(timer);
148         if (err < 0) {
149                 snd_timer_global_free(timer);
150                 return err;
151         }
152         mytimer = timer; /* remember this */
153
154         return 0;
155 }
156
157 static void __exit snd_hrtimer_exit(void)
158 {
159         if (mytimer) {
160                 snd_timer_global_free(mytimer);
161                 mytimer = NULL;
162         }
163 }
164
165 module_init(snd_hrtimer_init);
166 module_exit(snd_hrtimer_exit);