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/module.h>
23 #include <linux/moduleparam.h>
24 #include <linux/hrtimer.h>
25 #include <sound/core.h>
26 #include <sound/timer.h>
27
28 MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
29 MODULE_DESCRIPTION("ALSA hrtimer backend");
30 MODULE_LICENSE("GPL");
31
32 MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER));
33
34 #define NANO_SEC 1000000000UL /* 10^9 in sec */
35 static unsigned int resolution;
36
37 struct snd_hrtimer {
38 struct snd_timer *timer;
39 struct hrtimer hrt;
40 };
41
snd_hrtimer_callback(struct hrtimer * hrt)42 static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt)
43 {
44 struct snd_hrtimer *stime = container_of(hrt, struct snd_hrtimer, hrt);
45 struct snd_timer *t = stime->timer;
46 hrtimer_forward_now(hrt, ns_to_ktime(t->sticks * resolution));
47 snd_timer_interrupt(stime->timer, t->sticks);
48 return HRTIMER_RESTART;
49 }
50
snd_hrtimer_open(struct snd_timer * t)51 static int snd_hrtimer_open(struct snd_timer *t)
52 {
53 struct snd_hrtimer *stime;
54
55 stime = kmalloc(sizeof(*stime), GFP_KERNEL);
56 if (!stime)
57 return -ENOMEM;
58 hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
59 stime->timer = t;
60 stime->hrt.function = snd_hrtimer_callback;
61 t->private_data = stime;
62 return 0;
63 }
64
snd_hrtimer_close(struct snd_timer * t)65 static int snd_hrtimer_close(struct snd_timer *t)
66 {
67 struct snd_hrtimer *stime = t->private_data;
68
69 if (stime) {
70 hrtimer_cancel(&stime->hrt);
71 kfree(stime);
72 t->private_data = NULL;
73 }
74 return 0;
75 }
76
snd_hrtimer_start(struct snd_timer * t)77 static int snd_hrtimer_start(struct snd_timer *t)
78 {
79 struct snd_hrtimer *stime = t->private_data;
80
81 hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution),
82 HRTIMER_MODE_REL);
83 return 0;
84 }
85
snd_hrtimer_stop(struct snd_timer * t)86 static int snd_hrtimer_stop(struct snd_timer *t)
87 {
88 struct snd_hrtimer *stime = t->private_data;
89
90 hrtimer_cancel(&stime->hrt);
91 return 0;
92 }
93
94 static struct snd_timer_hardware hrtimer_hw = {
95 .flags = SNDRV_TIMER_HW_AUTO,
96 .open = snd_hrtimer_open,
97 .close = snd_hrtimer_close,
98 .start = snd_hrtimer_start,
99 .stop = snd_hrtimer_stop,
100 };
101
102 /*
103 * entry functions
104 */
105
106 static struct snd_timer *mytimer;
107
snd_hrtimer_init(void)108 static int __init snd_hrtimer_init(void)
109 {
110 struct snd_timer *timer;
111 struct timespec tp;
112 int err;
113
114 hrtimer_get_res(CLOCK_MONOTONIC, &tp);
115 if (tp.tv_sec > 0 || !tp.tv_nsec) {
116 snd_printk(KERN_ERR
117 "snd-hrtimer: Invalid resolution %u.%09u",
118 (unsigned)tp.tv_sec, (unsigned)tp.tv_nsec);
119 return -EINVAL;
120 }
121 resolution = tp.tv_nsec;
122
123 /* Create a new timer and set up the fields */
124 err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER,
125 &timer);
126 if (err < 0)
127 return err;
128
129 timer->module = THIS_MODULE;
130 strcpy(timer->name, "HR timer");
131 timer->hw = hrtimer_hw;
132 timer->hw.resolution = resolution;
133 timer->hw.ticks = NANO_SEC / resolution;
134
135 err = snd_timer_global_register(timer);
136 if (err < 0) {
137 snd_timer_global_free(timer);
138 return err;
139 }
140 mytimer = timer; /* remember this */
141
142 return 0;
143 }
144
snd_hrtimer_exit(void)145 static void __exit snd_hrtimer_exit(void)
146 {
147 if (mytimer) {
148 snd_timer_global_free(mytimer);
149 mytimer = NULL;
150 }
151 }
152
153 module_init(snd_hrtimer_init);
154 module_exit(snd_hrtimer_exit);
155