[alsa-devel] ASoC : question about custom rate

Matt Flax flatmax at flatmax.org
Tue Sep 9 10:43:36 CEST 2014


Hi there,

I have an ASIC running on an ASoC with a custom rate @ 18750 Hz.
I would like ALSA to report the correct rate.

If I do nothing, then the following reports 16000 Hz :
cat /proc/asound/card0/pcm0c/sub0/hw_params

I have verified that the hardware is running at the expected 18750 Hz.
I am wondering what/where is the correct place to setup the actual rate ?

I am trying to set the rates at startup like so but ALSA will not work 
with the driver when I do this :

static int implant_startup(struct snd_pcm_substream *substream, struct 
snd_soc_dai *dai)
{
     snd_pcm_hw_constraint_minmax(substream->runtime, 
SNDRV_PCM_HW_PARAM_RATE, 18750, 18750);
     snd_pcm_hw_constraint_minmax(substream->runtime, 
SNDRV_PCM_HW_PARAM_CHANNELS, 2, 2);
     snd_pcm_hw_constraint_minmax(substream->runtime, 
SNDRV_PCM_HW_PARAM_SAMPLE_BITS, 16, 16);

     return 0;
}

static const struct snd_soc_dai_ops implant_dai_ops = {
     .set_fmt    = implant_set_dai_fmt,
     .startup = implant_startup,
};

thanks
Matt


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