linux-kernel - Re: [PATCH v4 2/3] hwrng: add Rockchip SoC hwrng driver

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Date: Sun, 23 Jun 2024 11:46:25 +0200
From: Uwe Kleine-König <ukleinek@...ian.org>
To: 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>,
 Sascha Hauer <s.hauer@...gutronix.de>, Dragan Simic <dsimic@...jaro.org>,
 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 v4 2/3] hwrng: add Rockchip SoC hwrng driver

Hello Krzysztof,

On 6/23/24 09:00, Krzysztof Kozlowski wrote:
> On 23/06/2024 05:33, Daniel Golle wrote:
>> +
>> +	pm_runtime_set_autosuspend_delay(dev, RK_RNG_AUTOSUSPEND_DELAY);
>> +	pm_runtime_use_autosuspend(dev);
>> +	devm_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_dbg(&pdev->dev, "Registered Rockchip hwrng\n");
> 
> Drop, it is not useful at all. Srsly, we had already long enough talk,
 > [...]

And in this long talk using dev_dbg() was one of the suggestions for a 
compromise. For me this is ok.

> There is no single benefit of such debug statement. sysfs already
> provides you this information. Simple entry/exit  is provided by
> tracing. You duplicate existing interfaces without any benefit, because
> this prints nothing more.

There might be a (small) value if you want to know when during boot the 
device becomes available. So having a dev_dbg() that can be enabled 
dynamically (assuming DYNAMIC_DEBUG=y) and isn't in the way otherwise 
might be justified. IMHO a dev_dbg is lightweight enough that *I* won't 
continue the discussion.

Best regards
Uwe