linux-kernel - Re: [PATCH v2 1/2] hwmon: (pwm-fan) add option to leave fan on shutdown

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Message-ID: <baaee942-b46c-468b-9f81-3b9c8b1f9ef3@roeck-us.net>
Date: Wed, 30 Oct 2024 08:30:03 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Akinobu Mita <akinobu.mita@...il.com>
Cc: Billy Tsai <billy_tsai@...eedtech.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 Jean Delvare <jdelvare@...e.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Subject: Re: [PATCH v2 1/2] hwmon: (pwm-fan) add option to leave fan on
 shutdown

On 10/30/24 08:18, Akinobu Mita wrote:
> 2024年10月31日(木) 0:02 Guenter Roeck <linux@...ck-us.net>:
>>
>> On 10/30/24 07:55, Akinobu Mita wrote:
>>> 2024年10月29日(火) 11:35 Billy Tsai <billy_tsai@...eedtech.com>:
>>>>
>>>>> This adds an optional property "retain-state-shutdown" as requested by
>>>>> Billy Tsai.
>>>>
>>>>> Billy said:
>>>>>    "Our platform is BMC that will use a PWM-FAN driver to control the fan
>>>>>    on the managed host. In our case, we do not want to stop the fan when
>>>>>    the BMC is reboot, which may cause the temperature of the managed host
>>>>>    not to be lowered."
>>>>
>>>> I confirmed that it works properly.
>>>>
>>>> Reviewed-by: Billy Tsai <billy_tsai@...eedtech.com>
>>>> Tested-by: Billy Tsai <billy_tsai@...eedtech.com>
>>>
>>> Thank you very much for testing.
>>> However, I plan to change this option to device attribute
>>> (/sys/class/hwmon/hwmonX/retain-state-shutdown) instead of the device tree.
>>
>>
>> No, I won't acccept that.
> 
> Oops, I mean /sys/device/platform/pwm-fan.X/retain-state-shutdown
> not /sys/class/hwmon/hwmonX/retain-state-shutdown.

That does not make a difference. It still very much looks like a system property
to me, and making it a device property to be set by userspace just looks like
a workaround to address refusal by dt maintainers to accept the system property.

You'll have to make the case for why this is _not_ a system property for me
to accept it.

Guenter