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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); |
167 |
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