linux-kernel - Re: [PATCH 1/3] media: qcom: camss: vfe: Stop spamming logs with version

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Message-ID: <aCw09Vci12txhYj-@hovoldconsulting.com>
Date: Tue, 20 May 2025 09:53:25 +0200
From: Johan Hovold <johan@...nel.org>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
	Robert Foss <rfoss@...nel.org>, Todor Tomov <todor.too@...il.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] media: qcom: camss: vfe: Stop spamming logs with
 version

On Tue, May 20, 2025 at 08:06:22AM +0200, Krzysztof Kozlowski wrote:
> On 30/04/2025 10:33, Krzysztof Kozlowski wrote:
> > On 30/04/2025 10:30, Bryan O'Donoghue wrote:
> >> On 30/04/2025 09:19, Krzysztof Kozlowski wrote:
> >>> If anyone wants to know it and cannot deduce from compatible, then add
> >>> debugfs interface.
> >>
> >> dev_dbg(); isn't too offensive really IMO but if it really bothers you 
> >> switching to debugfs would be fine.
> > 
> > Yes, please. Dmesg should be only contain issues or some useful
> > debugging data. Probe success is not useful. It duplicates sysfs and
> > tracing. Version of hardware - well, I am sure it duplicates the compatible.
> 
> To recall: kernel coding style is also clear here:
> "When drivers are working properly they are quiet,"

That's clear and well known (or should be).

> and kernel debugging guide as well:
> "In almost all cases the debug statements shouldn't be upstreamed, as a
> working driver is supposed to be silent."

But this is a very recent addition and questionable when read in
isolation since debug statements are not printed by default. The
preceding sentences do qualify this:

	Permanent debug statements have to be useful for a developer to
	troubleshoot driver misbehavior. Judging that is a bit more of
	an art than a science...

> So I really do not get why this driver deserved exception. Nevertheless
> I think we agreed that these logs can go away, thus I just sent a v2
> with a bit extended commit msg.

Spamming the logs as the driver currently does is clearly broken and
should be fixed. Keeping a hw version dev_dbg() is generally perfectly
fine, though.

Johan