linux-kernel - Re: [PATCH 3/4] ASoC: codecs: tas5720: add TAS5722 specific volume control

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Message-ID: <20171212120121.GH16323@sirena.org.uk>
Date:   Tue, 12 Dec 2017 12:01:21 +0000
From:   Mark Brown <broonie@...nel.org>
To:     "Andrew F. Davis" <afd@...com>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] ASoC: codecs: tas5720: add TAS5722 specific volume
 control

On Mon, Dec 11, 2017 at 01:01:56PM -0600, Andrew F. Davis wrote:

> The TAS5722 supports modifying volume in 0.25dB steps (as opposed to 0.5dB
> steps on the TAS5720). Introduce a custom mixer control that allows taking
> advantage of this finer output volume granularity.

Don't do this, it's just making things more complicated.  Instead do
what other drivers do and register different sets of controls depending
on which part you're working with.  The normal thing is to have a big
table for all the shared controls that are the same on all variants then
register additional tables during probe with those that vary for the
individul devices.

>  static const struct snd_kcontrol_new tas5720_snd_controls[] = {
>  	SOC_SINGLE_TLV("Speaker Driver Playback Volume",
> -		       TAS5720_VOLUME_CTRL_REG, 0, 0xff, 0, dac_tlv),
> +		       TAS5720_VOLUME_CTRL_REG, 0, 0xff, 0, tas5720_dac_tlv),
> +	SOC_SINGLE_TLV("Speaker Driver Analog Gain", TAS5720_ANALOG_CTRL_REG,
> +		       TAS5720_ANALOG_GAIN_SHIFT, 3, 0, dac_analog_tlv),

As ever all volume controls should end in Volume (like the immediately
adjacent control does).

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