From: Thomas Preston <thomas.preston@codethink.co.uk>
To: Mark Brown <broonie@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
devicetree@vger.kernel.org, alsa-devel@alsa-project.org,
Charles Keepax <ckeepax@opensource.cirrus.com>,
Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>,
Kirill Marinushkin <kmarinushkin@birdec.tech>,
Liam Girdwood <lgirdwood@gmail.com>,
Marco Felsch <m.felsch@pengutronix.de>,
Annaliese McDermond <nh6z@nh6z.net>,
Takashi Iwai <tiwai@suse.com>,
Paul Cercueil <paul@crapouillou.net>,
Vinod Koul <vkoul@kernel.org>, Rob Herring <robh+dt@kernel.org>,
Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
Jerome Brunet <jbrunet@baylibre.com>,
linux-kernel@vger.kernel.org,
Cheng-Yi Chiang <cychiang@chromium.org>
Subject: Re: [alsa-devel] [PATCH v2 3/3] ASoC: TDA7802: Add turn-on diagnostic routine
Date: Tue, 30 Jul 2019 17:28:11 +0100 [thread overview]
Message-ID: <9b47a360-3b62-b968-b8d5-8639dc4b468d@codethink.co.uk> (raw)
In-Reply-To: <20190730155027.GJ4264@sirena.org.uk>
On 30/07/2019 16:50, Mark Brown wrote:
> 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.
>
Ah right, I understand. So if we run the turn-on diagnostics routine, there's
nothing stopping anyone from interacting with the device in other ways.
I guess there's no way to share that mutex with ALSA? In that case, it doesn't
matter if this mutex is there or not - this feature is incompatible. How
compatible do debugfs interfaces have to be? I was under the impression anything
goes. I would argue that the debugfs is better off for having the mutex so
that no one re-reads "diagnostic" within the 5s poll timeout.
Alternatively, this diagnostic feature could be handled with an external-handler
kcontrol SOC_SINGLE_EXT? I'm not sure if this is an atomic interface either.
What would be acceptable?
next prev parent reply other threads:[~2019-07-30 16:28 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-30 12:09 [PATCH v2 0/3] ASoC: Codecs: Add TDA7802 codec Thomas Preston
2019-07-30 12:09 ` [PATCH v2 1/3] dt-bindings: ASoC: Add TDA7802 amplifier Thomas Preston
2019-07-30 12:27 ` Charles Keepax
2019-07-30 13:12 ` Marco Felsch
2019-07-30 14:12 ` [alsa-devel] " Thomas Preston
2019-07-30 14:33 ` Mark Brown
2019-07-30 14:10 ` Thomas Preston
2019-07-30 12:09 ` [PATCH v2 2/3] ASoC: Add codec driver for ST TDA7802 Thomas Preston
2019-07-30 12:38 ` Charles Keepax
2019-07-30 15:49 ` [alsa-devel] " Thomas Preston
2019-07-30 14:58 ` Mark Brown
2019-07-30 17:26 ` [alsa-devel] " Thomas Preston
2019-07-31 6:06 ` Marco Felsch
2019-07-31 8:57 ` Thomas Preston
2019-07-30 12:09 ` [PATCH v2 3/3] ASoC: TDA7802: Add turn-on diagnostic routine Thomas Preston
2019-07-30 12:41 ` Charles Keepax
2019-07-30 14:04 ` [alsa-devel] " Thomas Preston
2019-07-30 14:18 ` Charles Keepax
2019-07-30 14:20 ` [alsa-devel] " Mark Brown
2019-07-30 15:27 ` Thomas Preston
2019-07-30 14:19 ` Mark Brown
2019-07-30 15:25 ` [alsa-devel] " Thomas Preston
2019-07-30 15:50 ` Mark Brown
2019-07-30 16:28 ` Thomas Preston [this message]
2019-07-31 8:03 ` Charles Keepax
2019-08-01 23:42 ` Mark Brown
2019-08-02 8:32 ` Thomas Preston
2019-08-02 11:10 ` Mark Brown
2019-08-02 14:51 ` Thomas Preston
2019-08-02 17:27 ` Mark Brown
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