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/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
  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
  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
  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
  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
  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
 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
 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);