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

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Date:   Mon, 15 Jan 2018 16:41:34 +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, Jan 15, 2018 at 08:50:09AM -0600, Andrew F. Davis wrote:
> On 12/12/2017 06:01 AM, Mark Brown wrote:
> > 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.

> That is what we are doing here, the reason for the custom mixer control
> is that the controlled bits span two registers in a odd way that is not
> supported by the standard handlers.

That's not clear from the commit message, it sounds like you're
introducing an an extra control rather than replacing the one that's
currently there.  

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

> This was done so this table exactly matches the existing table. If you
> would like me to change this then I can, and can do it for the other
> table as well, up to you.

Of course fixes for bugs in existing code are welcome.

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