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

[Mark Brown]

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.
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