linux-kernel - Re: [PATCH v3 2/3] hwrng: add Rockchip SoC hwrng driver

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Date: Sat, 22 Jun 2024 12:29:33 +0200
From: Dragan Simic <dsimic@...jaro.org>
To: Uwe Kleine-König <ukleinek@...nel.org>
Cc: Krzysztof Kozlowski <krzk@...nel.org>, Daniel Golle
 <daniel@...rotopia.org>, Aurelien Jarno <aurelien@...el32.net>, Olivia
 Mackall <olivia@...enic.com>, Herbert Xu <herbert@...dor.apana.org.au>, Rob
 Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor
 Dooley <conor+dt@...nel.org>, Heiko Stuebner <heiko@...ech.de>, Philipp
 Zabel <p.zabel@...gutronix.de>, Sebastian Reichel
 <sebastian.reichel@...labora.com>, Anand Moon <linux.amoon@...il.com>,
 Sascha Hauer <s.hauer@...gutronix.de>, Martin Kaiser <martin@...ser.cx>, Ard
 Biesheuvel <ardb@...nel.org>, linux-crypto@...r.kernel.org,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] hwrng: add Rockchip SoC hwrng driver

Hello Uwe,

On 2024-06-22 00:16, Uwe Kleine-König wrote:
> On 6/21/24 20:13, Dragan Simic wrote:
>> On 2024-06-21 11:57, Krzysztof Kozlowski wrote:
>>> On 21/06/2024 03:25, Daniel Golle wrote:
>>>> From: Aurelien Jarno <aurelien@...el32.net>
>> 
>> [snip]
>> 
>>>> +    pm_runtime_set_autosuspend_delay(dev, 
>>>> RK_RNG_AUTOSUSPEND_DELAY);
>>>> +    pm_runtime_use_autosuspend(dev);
>>>> +    pm_runtime_enable(dev);
>>>> +
>>>> +    ret = devm_hwrng_register(dev, &rk_rng->rng);
>>>> +    if (ret)
>>>> +        return dev_err_probe(&pdev->dev, ret, "Failed to register 
>>>> Rockchip hwrng\n");
>>>> +
>>>> +    dev_info(&pdev->dev, "Registered Rockchip hwrng\n");
>>> 
>>> Drop, driver should be silent on success.
>> 
>> I respectfully disagree.  Many drivers print a single line upon
>> successful probing, which I find very useful.  In this particular
>> case, it's even more useful, because some people may be concerned
>> about the use of hardware TRNGs, so we should actually make sure
>> to announce it.
> 
> I agree to Krzysztof here. From the POV of a driver author, your own
> driver is very important and while you write it, it really interests
> *you* if the driver is successfully probed. However from a system
> perspective these are annoying: There are easily >50 devices[1] on a
> system, if all of these print a message in probe, you have little 
> chance
> to see the relevant messages. Even if every driver author thinks their
> work is a special snow flake that is worth announcing, in practice 
> users
> only care about your driver if there is a problem. Additionally each
> message takes time and so delays the boot process. Additionally each
> message takes place in the printk ring buffer and so edges out earlier
> messages that might be more important.

Well, I don't find those messages annoying, for the drivers I've had
nothing to do with.  Also, in my experience, 99.9% of users don't care
about the kernel messages at all, be it everything hunky-dory, or be
it something really wrong somewhere.

> So +1 for dropping the dev_info() or at least using dev_debug() for it.
> 
> Best regards
> Uwe
> 
> [1] On my laptop if have:
> 
> 	$ find /sys/devices -name driver | wc -l
> 	87
> 
>     On a Raspberrypi it yields 66.