linux-kernel - Re: [PATCH v2 2/2] dt-bindings: hwmon: pwm-fan: add retain-state-shutdown property

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Message-ID: <e4985609-0642-4ff4-b074-8c5a34f88a24@kernel.org>
Date: Wed, 30 Oct 2024 16:18:19 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Akinobu Mita <akinobu.mita@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
 devicetree@...r.kernel.org, Jean Delvare <jdelvare@...e.com>,
 Guenter Roeck <linux@...ck-us.net>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Billy Tsai <billy_tsai@...eedtech.com>
Subject: Re: [PATCH v2 2/2] dt-bindings: hwmon: pwm-fan: add
 retain-state-shutdown property

On 28/10/2024 15:57, Akinobu Mita wrote:
>>>>
>>>> You described the desired Linux feature or behavior, not the actual
>>>> hardware. The bindings are about the latter, so instead you need to
>>>> rephrase the property and its description to match actual hardware
>>>> capabilities/features/configuration etc.
>>>
>>> Is this description okay?
>>> (Reused the description of retain-state-shutdown in leds-gpio.yaml)
>>>
>>> description:
>>>   Retain the state of the PWM on shutdown. Useful in BMC systems, for
>>>   example, when the BMC is rebooted while the host remains up, the fan
>>>   will not stop.
>>
>> Nothing improved in the property. You still say what the system should
>> do. This is user-space choice, not DT.
> 
> It seems better to implement it as a device attribute.

I don't know about that. To repeat: if you say what system is supposed
to be doing, it is a policy. Describe the hardware and its configuration
and maybe this would be suitable for DT.

Best regards,
Krzysztof