linux-kernel - Re: [PATCH v2 1/3] ASoC: wm8782: Handle maximum audio rate at runtime

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Message-ID: <ZQLR50CAzr0VDpeh@titan>
Date:   Thu, 14 Sep 2023 19:27:03 +1000
From:   John Watts <contact@...kia.org>
To:     Charles Keepax <ckeepax@...nsource.cirrus.com>
Cc:     alsa-devel@...a-project.org, Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, patches@...nsource.cirrus.com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] ASoC: wm8782: Handle maximum audio rate at runtime

On Thu, Sep 14, 2023 at 09:21:07AM +0000, Charles Keepax wrote:
> On Thu, Sep 14, 2023 at 03:15:50AM +1000, John Watts wrote:
> > The wm8782 supports up to 192kHz audio when pins are set correctly.
> > Instead of hardcoding which rates are supported enable them all
> > then refer to a max_rate variable at runtime.
> > 
> > Signed-off-by: John Watts <contact@...kia.org>
> > ---
> > +static int wm8782_dai_hw_params(struct snd_pcm_substream *component,
> > +			    struct snd_pcm_hw_params *params,
> > +			    struct snd_soc_dai *dai)
> > +{
> > +	struct wm8782_priv *priv =
> > +		snd_soc_component_get_drvdata(dai->component);
> > +
> > +	if (params_rate(params) > priv->max_rate)
> > +		return -EINVAL;
> > +
> > +	return 0;
> > +}
> 
> We should be setting this as a constraint in startup, rather
> than returning an error in hw_params. That will let user-space
> know the supported rates and allow it to resample if necessary.

How do you do this? The struct with the rate is statically defined.

> 
> Thanks,
> Charles

John.