linux-kernel - Re: [PATCH 1/3] pinctrl: cix: Add pin-controller support for sky1

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Message-ID: <67e58bda-3cac-4689-831a-4e4116a0e19b@kernel.org>
Date: Thu, 28 Aug 2025 20:02:31 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: Gary Yang <gary.yang@...tech.com>, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, cix-kernel-upstream@...tech.com
Subject: Re: [PATCH 1/3] pinctrl: cix: Add pin-controller support for sky1

On 28/08/2025 19:51, Linus Walleij wrote:
> On Wed, Aug 27, 2025 at 11:07 AM Krzysztof Kozlowski <krzk@...nel.org> wrote:
>> On 27/08/2025 04:42, Gary Yang wrote:
> 
>>> +     pinctrl_provide_dummies();
>>> +     dev_info(&pdev->dev, "initialized SKY1 pinctrl driver\n");
>>
>>
>> No, please drop. Drivers should be silent on success.
> 
> I usually think this is a matter of taste.

It's actually coding style:
https://elixir.bootlin.com/linux/v6.15-rc1/source/Documentation/process/coding-style.rst#L913

https://elixir.bootlin.com/linux/v6.15-rc1/source/Documentation/process/debugging/driver_development_debugging_guide.rst#L79

https://lore.kernel.org/all/20191210143706.3928480-6-gregkh@linuxfoundation.org/

> 
> I suppose the reason why a lot of drivers have some "hello world" message
> is that missing probe calls is sometimes an issue.
> 
> If you mistakenly disable the driver in Kconfig (or due to other Kconfig
> changes that just happen ...), how do you know from the dmesg
> what error you made, when comparing it to a successful boot. There
> are no *error* messages from the driver either, just the same silence as
> when it's enabled. With pinctrl, random completely unrelated stuff just
> stops working.
> 
> If you see that the "hello world" from that driver is missing, you know it
> isn't probing, instead of finding it out after combing through the .config
> for the third time.

Any tests for driver success should be checking in sysfs, not in dmesg.
Most of platforms have smaller or bigger tests for that.

> 
> But I know a lot of people are dmesg minimalists, because it's just too
> much information and they just want errors there. It makes sense in a
> way too.
> 
> So as subsystem maintainer I have no hard opinion on it.

Best regards,
Krzysztof