sound/core/pcm_timer.c

   1 /*
   2  *  Digital Audio (PCM) abstract layer
   3  *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
   4  *
   5  *
   6  *   This program is free software; you can redistribute it and/or modify
   7  *   it under the terms of the GNU General Public License as published by
   8  *   the Free Software Foundation; either version 2 of the License, or
   9  *   (at your option) any later version.
  10  *
  11  *   This program is distributed in the hope that it will be useful,
  12  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *   GNU General Public License for more details.
  15  *
  16  *   You should have received a copy of the GNU General Public License
  17  *   along with this program; if not, write to the Free Software
  18  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  19  *
  20  */
  21
  22 #include <linux/time.h>
  23 #include <sound/core.h>
  24 #include <sound/pcm.h>
  25 #include <sound/timer.h>
  26
  27 /*
  28  *  Timer functions
  29  */
  30
  31 /* Greatest common divisor */
  32 static unsigned long gcd(unsigned long a, unsigned long b)
  33 {
  34         unsigned long r;
  35         if (a < b) {
  36                 r = a;
  37                 a = b;
  38                 b = r;
  39         }
  40         while ((r = a % b) != 0) {
  41                 a = b;
  42                 b = r;
  43         }
  44         return b;
  45 }
  46
  47 void snd_pcm_timer_resolution_change(struct snd_pcm_substream *substream)
  48 {
  49         unsigned long rate, mult, fsize, l, post;
  50         struct snd_pcm_runtime *runtime = substream->runtime;
  51
  52         mult = 1000000000;
  53         rate = runtime->rate;
  54         if (snd_BUG_ON(!rate))
  55                 return;
  56         l = gcd(mult, rate);
  57         mult /= l;
  58         rate /= l;
  59         fsize = runtime->period_size;
  60         if (snd_BUG_ON(!fsize))
  61                 return;
  62         l = gcd(rate, fsize);
  63         rate /= l;
  64         fsize /= l;
  65         post = 1;
  66         while ((mult * fsize) / fsize != mult) {
  67                 mult /= 2;
  68                 post *= 2;
  69         }
  70         if (rate == 0) {
  71                 snd_printk(KERN_ERR "pcm timer resolution out of range (rate = %u, period_size = %lu)\n", runtime->rate, runtime->period_size);
  72                 runtime->timer_resolution = -1;
  73                 return;
  74         }
  75         runtime->timer_resolution = (mult * fsize / rate) * post;
  76 }
  77
  78 static unsigned long snd_pcm_timer_resolution(struct snd_timer * timer)
  79 {
  80         struct snd_pcm_substream *substream;
  81
  82         substream = timer->private_data;
  83         return substream->runtime ? substream->runtime->timer_resolution : 0;
  84 }
  85
  86 static int snd_pcm_timer_start(struct snd_timer * timer)
  87 {
  88         struct snd_pcm_substream *substream;
  89
  90         substream = snd_timer_chip(timer);
  91         substream->timer_running = 1;
  92         return 0;
  93 }
  94
  95 static int snd_pcm_timer_stop(struct snd_timer * timer)
  96 {
  97         struct snd_pcm_substream *substream;
  98
  99         substream = snd_timer_chip(timer);
 100         substream->timer_running = 0;
 101         return 0;
 102 }
 103
 104 static struct snd_timer_hardware snd_pcm_timer =
 105 {
 106         .flags =        SNDRV_TIMER_HW_AUTO | SNDRV_TIMER_HW_SLAVE,
 107         .resolution =   0,
 108         .ticks =        1,
 109         .c_resolution = snd_pcm_timer_resolution,
 110         .start =        snd_pcm_timer_start,
 111         .stop =         snd_pcm_timer_stop,
 112 };
 113
 114 /*
 115  *  Init functions
 116  */
 117
 118 static void snd_pcm_timer_free(struct snd_timer *timer)
 119 {
 120         struct snd_pcm_substream *substream = timer->private_data;
 121         substream->timer = NULL;
 122 }
 123
 124 void snd_pcm_timer_init(struct snd_pcm_substream *substream)
 125 {
 126         struct snd_timer_id tid;
 127         struct snd_timer *timer;
 128
 129         tid.dev_sclass = SNDRV_TIMER_SCLASS_NONE;
 130         tid.dev_class = SNDRV_TIMER_CLASS_PCM;
 131         tid.card = substream->pcm->card->number;
 132         tid.device = substream->pcm->device;
 133         tid.subdevice = (substream->number << 1) | (substream->stream & 1);
 134         if (snd_timer_new(substream->pcm->card, "PCM", &tid, &timer) < 0)
 135                 return;
 136         sprintf(timer->name, "PCM %s %i-%i-%i",
 137                         substream->stream == SNDRV_PCM_STREAM_CAPTURE ?
 138                                 "capture" : "playback",
 139                         tid.card, tid.device, tid.subdevice);
 140         timer->hw = snd_pcm_timer;
 141         if (snd_device_register(timer->card, timer) < 0) {
 142                 snd_device_free(timer->card, timer);
 143                 return;
 144         }
 145         timer->private_data = substream;
 146         timer->private_free = snd_pcm_timer_free;
 147         substream->timer = timer;
 148 }
 149
 150 void snd_pcm_timer_done(struct snd_pcm_substream *substream)
 151 {
 152         if (substream->timer) {
 153                 snd_device_free(substream->pcm->card, substream->timer);
 154                 substream->timer = NULL;
 155         }
 156 }