Re: [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:

quoted

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.