1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Digital Audio (PCM) abstract layer
4 * Copyright (c) by Jaroslav Kysela <perex@perex.cz>
5 */
6
7#include <linux/time.h>
8#include <linux/gcd.h>
9#include <sound/core.h>
10#include <sound/pcm.h>
11#include <sound/timer.h>
12
13#include "pcm_local.h"
14
15/*
16 * Timer functions
17 */
18
19void snd_pcm_timer_resolution_change(struct snd_pcm_substream *substream)
20{
21 unsigned long rate, mult, fsize, l, post;
22 struct snd_pcm_runtime *runtime = substream->runtime;
23
24 mult = 1000000000;
25 rate = runtime->rate;
26 if (snd_BUG_ON(!rate))
27 return;
28 l = gcd(a: mult, b: rate);
29 mult /= l;
30 rate /= l;
31 fsize = runtime->period_size;
32 if (snd_BUG_ON(!fsize))
33 return;
34 l = gcd(a: rate, b: fsize);
35 rate /= l;
36 fsize /= l;
37 post = 1;
38 while ((mult * fsize) / fsize != mult) {
39 mult /= 2;
40 post *= 2;
41 }
42 if (rate == 0) {
43 pcm_err(substream->pcm,
44 "pcm timer resolution out of range (rate = %u, period_size = %lu)\n",
45 runtime->rate, runtime->period_size);
46 runtime->timer_resolution = -1;
47 return;
48 }
49 runtime->timer_resolution = (mult * fsize / rate) * post;
50}
51
52static unsigned long snd_pcm_timer_resolution(struct snd_timer * timer)
53{
54 struct snd_pcm_substream *substream;
55
56 substream = timer->private_data;
57 return substream->runtime ? substream->runtime->timer_resolution : 0;
58}
59
60static int snd_pcm_timer_start(struct snd_timer * timer)
61{
62 struct snd_pcm_substream *substream;
63
64 substream = snd_timer_chip(timer);
65 substream->timer_running = 1;
66 return 0;
67}
68
69static int snd_pcm_timer_stop(struct snd_timer * timer)
70{
71 struct snd_pcm_substream *substream;
72
73 substream = snd_timer_chip(timer);
74 substream->timer_running = 0;
75 return 0;
76}
77
78static const struct snd_timer_hardware snd_pcm_timer =
79{
80 .flags = SNDRV_TIMER_HW_AUTO | SNDRV_TIMER_HW_SLAVE,
81 .resolution = 0,
82 .ticks = 1,
83 .c_resolution = snd_pcm_timer_resolution,
84 .start = snd_pcm_timer_start,
85 .stop = snd_pcm_timer_stop,
86};
87
88/*
89 * Init functions
90 */
91
92static void snd_pcm_timer_free(struct snd_timer *timer)
93{
94 struct snd_pcm_substream *substream = timer->private_data;
95 substream->timer = NULL;
96}
97
98void snd_pcm_timer_init(struct snd_pcm_substream *substream)
99{
100 struct snd_timer_id tid;
101 struct snd_timer *timer;
102
103 tid.dev_sclass = SNDRV_TIMER_SCLASS_NONE;
104 tid.dev_class = SNDRV_TIMER_CLASS_PCM;
105 tid.card = substream->pcm->card->number;
106 tid.device = substream->pcm->device;
107 tid.subdevice = (substream->number << 1) | (substream->stream & 1);
108 if (snd_timer_new(card: substream->pcm->card, id: "PCM", tid: &tid, rtimer: &timer) < 0)
109 return;
110 sprintf(buf: timer->name, fmt: "PCM %s %i-%i-%i",
111 snd_pcm_direction_name(direction: substream->stream),
112 tid.card, tid.device, tid.subdevice);
113 timer->hw = snd_pcm_timer;
114 if (snd_device_register(card: timer->card, device_data: timer) < 0) {
115 snd_device_free(card: timer->card, device_data: timer);
116 return;
117 }
118 timer->private_data = substream;
119 timer->private_free = snd_pcm_timer_free;
120 substream->timer = timer;
121}
122
123void snd_pcm_timer_done(struct snd_pcm_substream *substream)
124{
125 if (substream->timer) {
126 snd_device_free(card: substream->pcm->card, device_data: substream->timer);
127 substream->timer = NULL;
128 }
129}
130

source code of linux/sound/core/pcm_timer.c