LXR linux/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
  28MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
  29MODULE_DESCRIPTION("ALSA hrtimer backend");
  30MODULE_LICENSE("GPL");
  31
  32MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER));
  33
  34#define NANO_SEC        1000000000UL    /* 10^9 in sec */
  35static unsigned int resolution;
  36
  37struct snd_hrtimer {
  38        struct snd_timer *timer;
  39        struct hrtimer hrt;
  40};
  41
  42static 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
  51static 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
  65static 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
  77static 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
  86static 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
  94static 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
 106static struct snd_timer *mytimer;
 107
 108static 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
 145static void __exit snd_hrtimer_exit(void)
 146{
 147        if (mytimer) {
 148                snd_timer_global_free(mytimer);
 149                mytimer = NULL;
 150        }
 151}
 152
 153module_init(snd_hrtimer_init);
 154module_exit(snd_hrtimer_exit);
 155