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pcm: add pcm_get_params API

This enables the capabilities of any given PCM to be queried.

Created with input from Priyesh Bisla and Gabriel Beddingfield.
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1 parent 2c3a8e2 commit 43544884f44313176621f57b370b4ba114fe5b8c Simon Wilson committed Oct 31, 2012
Showing with 170 additions and 0 deletions.
  1. +26 −0 include/tinyalsa/asoundlib.h
  2. +144 −0 pcm.c
@@ -98,6 +98,23 @@ struct pcm_config {
unsigned int silence_threshold;
};
+/* PCM parameters */
+enum pcm_param
+{
+ PCM_PARAM_SAMPLE_BITS,
+ PCM_PARAM_FRAME_BITS,
+ PCM_PARAM_CHANNELS,
+ PCM_PARAM_RATE,
+ PCM_PARAM_PERIOD_TIME,
+ PCM_PARAM_PERIOD_SIZE,
+ PCM_PARAM_PERIOD_BYTES,
+ PCM_PARAM_PERIODS,
+ PCM_PARAM_BUFFER_TIME,
+ PCM_PARAM_BUFFER_SIZE,
+ PCM_PARAM_BUFFER_BYTES,
+ PCM_PARAM_TICK_TIME,
+};
+
/* Mixer control types */
enum mixer_ctl_type {
MIXER_CTL_TYPE_BOOL,
@@ -117,6 +134,15 @@ struct pcm *pcm_open(unsigned int card, unsigned int device,
int pcm_close(struct pcm *pcm);
int pcm_is_ready(struct pcm *pcm);
+/* Obtain the parameters for a PCM */
+struct pcm_params *pcm_params_get(unsigned int card, unsigned int device,
+ unsigned int flags);
+void pcm_params_free(struct pcm_params *pcm_params);
+unsigned int pcm_params_get_min(struct pcm_params *pcm_params,
+ enum pcm_param param);
+unsigned int pcm_params_get_max(struct pcm_params *pcm_params,
+ enum pcm_param param);
+
/* Set and get config */
int pcm_get_config(struct pcm *pcm, struct pcm_config *config);
int pcm_set_config(struct pcm *pcm, struct pcm_config *config);
View
144 pcm.c
@@ -93,6 +93,24 @@ static void param_set_min(struct snd_pcm_hw_params *p, int n, unsigned int val)
}
}
+static unsigned int param_get_min(struct snd_pcm_hw_params *p, int n)
+{
+ if (param_is_interval(n)) {
+ struct snd_interval *i = param_to_interval(p, n);
+ return i->min;
+ }
+ return 0;
+}
+
+static unsigned int param_get_max(struct snd_pcm_hw_params *p, int n)
+{
+ if (param_is_interval(n)) {
+ struct snd_interval *i = param_to_interval(p, n);
+ return i->max;
+ }
+ return 0;
+}
+
static void param_set_int(struct snd_pcm_hw_params *p, int n, unsigned int val)
{
if (param_is_interval(n)) {
@@ -130,6 +148,9 @@ static void param_init(struct snd_pcm_hw_params *p)
i->min = 0;
i->max = ~0;
}
+ p->rmask = ~0U;
+ p->cmask = 0;
+ p->info = ~0U;
}
#define PCM_ERROR_MAX 128
@@ -423,6 +444,129 @@ static struct pcm bad_pcm = {
.fd = -1,
};
+struct pcm_params *pcm_params_get(unsigned int card, unsigned int device,
+ unsigned int flags)
+{
+ struct snd_pcm_hw_params *params;
+ char fn[256];
+ int fd;
+
+ snprintf(fn, sizeof(fn), "/dev/snd/pcmC%uD%u%c", card, device,
+ flags & PCM_IN ? 'c' : 'p');
+
+ fd = open(fn, O_RDWR);
+ if (fd < 0) {
+ fprintf(stderr, "cannot open device '%s'\n", fn);
+ goto err_open;
+ }
+
+ params = calloc(1, sizeof(struct snd_pcm_hw_params));
+ if (!params)
+ goto err_calloc;
+
+ param_init(params);
+ if (ioctl(fd, SNDRV_PCM_IOCTL_HW_REFINE, params)) {
+ fprintf(stderr, "SNDRV_PCM_IOCTL_HW_REFINE error (%d)\n", errno);
+ goto err_hw_refine;
+ }
+
+ close(fd);
+
+ return (struct pcm_params *)params;
+
+err_hw_refine:
+ free(params);
+err_calloc:
+ close(fd);
+err_open:
+ return NULL;
+}
+
+void pcm_params_free(struct pcm_params *pcm_params)
+{
+ struct snd_pcm_hw_params *params = (struct snd_pcm_hw_params *)pcm_params;
+
+ if (params)
+ free(params);
+}
+
+static int pcm_param_to_alsa(enum pcm_param param)
+{
+ switch (param) {
+ case PCM_PARAM_SAMPLE_BITS:
+ return SNDRV_PCM_HW_PARAM_SAMPLE_BITS;
+ break;
+ case PCM_PARAM_FRAME_BITS:
+ return SNDRV_PCM_HW_PARAM_FRAME_BITS;
+ break;
+ case PCM_PARAM_CHANNELS:
+ return SNDRV_PCM_HW_PARAM_CHANNELS;
+ break;
+ case PCM_PARAM_RATE:
+ return SNDRV_PCM_HW_PARAM_RATE;
+ break;
+ case PCM_PARAM_PERIOD_TIME:
+ return SNDRV_PCM_HW_PARAM_PERIOD_TIME;
+ break;
+ case PCM_PARAM_PERIOD_SIZE:
+ return SNDRV_PCM_HW_PARAM_PERIOD_SIZE;
+ break;
+ case PCM_PARAM_PERIOD_BYTES:
+ return SNDRV_PCM_HW_PARAM_PERIOD_BYTES;
+ break;
+ case PCM_PARAM_PERIODS:
+ return SNDRV_PCM_HW_PARAM_PERIODS;
+ break;
+ case PCM_PARAM_BUFFER_TIME:
+ return SNDRV_PCM_HW_PARAM_BUFFER_TIME;
+ break;
+ case PCM_PARAM_BUFFER_SIZE:
+ return SNDRV_PCM_HW_PARAM_BUFFER_SIZE;
+ break;
+ case PCM_PARAM_BUFFER_BYTES:
+ return SNDRV_PCM_HW_PARAM_BUFFER_BYTES;
+ break;
+ case PCM_PARAM_TICK_TIME:
+ return SNDRV_PCM_HW_PARAM_TICK_TIME;
+ break;
+
+ default:
+ return -1;
+ }
+}
+
+unsigned int pcm_params_get_min(struct pcm_params *pcm_params,
+ enum pcm_param param)
+{
+ struct snd_pcm_hw_params *params = (struct snd_pcm_hw_params *)pcm_params;
+ int p;
+
+ if (!params)
+ return 0;
+
+ p = pcm_param_to_alsa(param);
+ if (p < 0)
+ return 0;
+
+ return param_get_min(params, p);
+}
+
+unsigned int pcm_params_get_max(struct pcm_params *pcm_params,
+ enum pcm_param param)
+{
+ struct snd_pcm_hw_params *params = (struct snd_pcm_hw_params *)pcm_params;
+ int p;
+
+ if (!params)
+ return 0;
+
+ p = pcm_param_to_alsa(param);
+ if (p < 0)
+ return 0;
+
+ return param_get_max(params, p);
+}
+
int pcm_close(struct pcm *pcm)
{
if (pcm == &bad_pcm)

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