linux-kernel - Re: [PATCH 2/2] ASoC: add tda7419 audio processor driver

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Message-ID: <20180309152912.GF5252@sirena.org.uk>
Date:   Fri, 9 Mar 2018 15:29:12 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Matt Porter <mporter@...sulko.com>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.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 2/2] ASoC: add tda7419 audio processor driver

On Fri, Mar 09, 2018 at 09:35:48AM -0500, Matt Porter wrote:
> On Wed, Feb 28, 2018 at 11:00:38AM +0000, Mark Brown wrote:
> > On Tue, Feb 27, 2018 at 05:51:28PM -0500, Matt Porter wrote:

> > > +static struct snd_kcontrol_new tda7419_controls[] = {
> > > +SOC_ENUM("Main Source Select", soc_enum_main_src_sel),

> > Should this be a DAPM route?

> Ultimately yes. I initially took the path of ignoring DAPM support in
> interests of getting some clean done. Is it ok to merge DAPM support
> later or do you prefer just having it in the intitial driver? For
> routes, it'll include Main/Second source selects, the Rear Source
> switch, and Mix enable at least.

You definitely shouldn't be implementing things that should be in DAPM
as non-DAPM controls.

> > > +	regmap_write(tda7419->regmap, TDA7419_ATTENUATOR_SUB_REG, 0xe0);

> > This looks like it's setting default volumes - just leave those at the
> > chip defaults and let userspace handle setting them, what works for one
> > board may be totally inappropriate on another board and using the chip
> > default means we've got some fixed thing we don't need to discuss.

> This is actually setting the default/cache to the first mute value due
> to the assumption in my implementation of the tda7419-specific get/set
> for these registers. It simplified the code a bit to have these
> initialized like this. e.g. for the attenuator group of registers,
> x11xxxxx are all mute values, so 0xe0 is setting these regs to that
> first mute value to simplify things. I'll take another look at
> eliminating this. As it is, it does not change the fact that the actual
> reset value of 0xff is also mute from a user POV.

If it is useful it definitely needs a comment explaining what's
happening and that there's no practical change to the configuration.  It
would be nicer to be robust against the device getting a wider range of
values in the register but that seems plausible.

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