linux-kernel - Re: [PATCH] hwmon: (aquacomputer_d5next) Set fan to direct PWM mode when writing value

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Message-ID: <718f0dd9-121a-4885-8976-aaafa7c44f2d@roeck-us.net>
Date: Sat, 17 Feb 2024 10:24:50 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Aleksa Savic <savicaleksa83@...il.com>, linux-hwmon@...r.kernel.org
Cc: Jack Doan <me@...kdoan.com>, Jean Delvare <jdelvare@...e.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hwmon: (aquacomputer_d5next) Set fan to direct PWM mode
 when writing value

On 2/17/24 10:15, Aleksa Savic wrote:
> When setting a PWM value for a fan channel, ensure that the device
> is actually in direct PWM value mode, as it could be in PID, curve or
> fan following mode from previous user configurations. The byte
> signifying the channel mode is just behind the offset for the value.
> Otherwise, setting PWM speed might result in a no-op from the point
> of the user.
> 

You can require that a device is in manual mode when setting pwm
modes, and return an error if it isn't. However, changing the mode
to manual automatically when a pwm value is written is not acceptable.

Guenter