[alsa-devel] ASoC: multicodec: No matching channels with system with DACs and ADCs on same bus

[Lars-Peter Clausen]

On 11/10/2015 06:12 PM, Caleb Crome wrote:
> Hi again,
>   I have a system that has separate DACs and ADCs, as opposed to
> bidirectional CODECS.
> 
> The ADCs have a snd_soc_dai_driver structure that have a .capture
> field defined with a .rates parameter, and the DACs have a
> snd_soc_dai_driver structure that have a .playback field defined with
> a .rates parameter.
> 
> However, the ADCs have no .playback.rates, and the DACs have no
> .capture.rates. Even though the ADC can record at a given rate and the
> DAC can play at that same rate, the soc_pcm_init_runtime_hw function
> calculates the rates in this loop:
> 
> ------------------------------
>     /* first calculate min/max only for CODECs in the DAI link */
>     for (i = 0; i < rtd->num_codecs; i++) {
>         codec_dai_drv = rtd->codec_dais[i]->driver;
>         if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
>             codec_stream = &codec_dai_drv->playback;
>         else
>             codec_stream = &codec_dai_drv->capture;
>         chan_min = max(chan_min, codec_stream->channels_min);
>         chan_max = min(chan_max, codec_stream->channels_max);
>         rate_min = max(rate_min, codec_stream->rate_min);
>         rate_max = min_not_zero(rate_max, codec_stream->rate_max);
>         formats &= codec_stream->formats;
>         rates = snd_pcm_rate_mask_intersect(codec_stream->rates, rates);
>     }
> ------------------------------
> 
> which can't work out that one side is play only and the other is
> record only, yet they do in fact have matching rates.  So, I get a "no
> matching channels" error.
[...]

Try the latest asoc/for-next kernel. There is a patch[1] that addresses the
issue.

- Lars

[1]
http://git.kernel.org/cgit/linux/kernel/git/broonie/sound.git/commit/sound/soc/soc-pcm.c?h=for-next&id=cde79035c6cf578dd33dfea3e39666efc27cbcf2