Re: [alsa-devel] [PATCH] ASoC: fsl_asrc: add protection for the asrc of older version

On Fri, Mar 01, 2019 at 06:55:25AM +0000, S.j. Wang wrote:

...

Alternatively, I feel instead of error-out at here, should we add a HW constraint or at least fence it off at the beginning of the hw_params()? This is actually nothing specific to the pair-request function but a hardware constraint.

How about add constraint in startup? static int fsl_asrc_dai_startup(struct snd_pcm_substream *substream, struct snd_soc_dai *dai) { struct fsl_asrc *asrc_priv = snd_soc_dai_get_drvdata(dai);

   if (asrc_priv->channel_bits == 3) {
           snd_pcm_hw_constraint_step(substream->runtime, 0,
                                      SNDRV_PCM_HW_PARAM_CHANNELS, 2);
   }

   return 0;

}

Yes, that's definitely good - the general idea is that we should never need to return an error from hw_params() as the constraints code will have filtered out any invalid configurations before they get that far.