linux-kernel - Re: [alsa-devel] [PATCH v2 3/3] ASoC: TDA7802: Add turn-on diagnostic routine

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Message-ID: <20190802111036.GB5387@sirena.org.uk>
Date:   Fri, 2 Aug 2019 12:10:36 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Thomas Preston <thomas.preston@...ethink.co.uk>
Cc:     Mark Rutland <mark.rutland@....com>, devicetree@...r.kernel.org,
        alsa-devel@...a-project.org,
        Charles Keepax <ckeepax@...nsource.cirrus.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        Kirill Marinushkin <kmarinushkin@...dec.tech>,
        Liam Girdwood <lgirdwood@...il.com>,
        Marco Felsch <m.felsch@...gutronix.de>,
        Annaliese McDermond <nh6z@...z.net>,
        Takashi Iwai <tiwai@...e.com>,
        Paul Cercueil <paul@...pouillou.net>,
        Vinod Koul <vkoul@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Jerome Brunet <jbrunet@...libre.com>,
        linux-kernel@...r.kernel.org,
        Cheng-Yi Chiang <cychiang@...omium.org>
Subject: Re: [alsa-devel] [PATCH v2 3/3] ASoC: TDA7802: Add turn-on
 diagnostic routine

On Fri, Aug 02, 2019 at 09:32:17AM +0100, Thomas Preston wrote:
> On 02/08/2019 00:42, Mark Brown wrote:

> > Yes, that's definitely doable - we've got some other drivers with
> > similar things like calibration triggers exposed that way.

> One problem with using a kcontrol as a trigger for the turn-on diagnostic
> is that the diagnostic routine has a "return value".

You can use a read only control for the readback, or just have it be
triggered by overwriting the readback value.  You can cache the result.

> Hm, maybe a better idea is to have the turn on diagnostic only run on
> device probe (as its name suggests!), and print something to dmesg:

> 	modprobe tda7802 turn_on_diagnostic=1

> 	tda7802-codec i2c-TDA7802:00: Turn on diagnostic 04 04 04 04

> Kirill Marinushkin mentioned this in the first review [0], it just didn't
> really sink in until now!

You could do that too, yeah.  Depends on what this is diagnosing and if
that'd be useful.

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