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

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Message-ID: <20190730155027.GJ4264@sirena.org.uk>
Date:   Tue, 30 Jul 2019 16:50:27 +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>,
        Cheng-Yi Chiang <cychiang@...omium.org>,
        Marco Felsch <m.felsch@...gutronix.de>,
        Takashi Iwai <tiwai@...e.com>,
        Annaliese McDermond <nh6z@...z.net>,
        Liam Girdwood <lgirdwood@...il.com>,
        Paul Cercueil <paul@...pouillou.net>,
        Vinod Koul <vkoul@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        linux-kernel@...r.kernel.org, Jerome Brunet <jbrunet@...libre.com>
Subject: Re: [alsa-devel] [PATCH v2 3/3] ASoC: TDA7802: Add turn-on
 diagnostic routine

On Tue, Jul 30, 2019 at 04:25:56PM +0100, Thomas Preston wrote:
> On 30/07/2019 15:19, Mark Brown wrote:

> > It is unclear what this mutex usefully protects, it only gets taken when
> > writing to the debugfs file to trigger this diagnostic mode but doesn't
> > do anything to control interactions with any other code path in the
> > driver.

> If another process reads the debugfs node "diagnostic" while the turn-on 
> diagnostic mode is running, this mutex prevents the second process
> restarting the diagnostics.

> This is redundant if debugfs reads are atomic, but I don't think they are.

Like I say it's not just debugfs though, there's the standard driver
interface too.

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