Re: [hwmon-next PATCH v4 3/4] hwmon: (adt7470) Expose fan control via PWM framework
From: Guenter Roeck
Date: Wed Jul 29 2026 - 10:44:12 EST
On 7/29/26 04:49, Uwe Kleine-König wrote:
On Tue, Jul 28, 2026 at 10:56:04PM -0700, Guenter Roeck wrote:It is my call to make, and my call is either-or to avoid confusion.
On 7/28/26 21:46, Luiz Angelo Daros de Luca wrote:
The ADT7470 features four PWM outputs designed to control fans.
Previously, these were only accessible through the legacy hwmon
sysfs interface.
Expose the ADT7470 fan control lines through the generic PWM framework.
This allows generic PWM consumers described in Device Tree, such as
"pwm-fan", to use the device through the "#pwm-cells" property. This is
particularly necessary for boards where the ADT7470 external temperature
sensors are not populated and the chip is used strictly as a fan
controller (e.g., Edgecore ECS-2100-52T switches). In such setups,
delegating control to the generic PWM subsystem allows the kernel's
thermal framework to manage the fans based on unrelated temperature
zones, such as internal SoC sensors.
When a PWM consumer applies a new PWM state, the driver automatically
switches the corresponding PWM channel to manual mode so that the
requested duty cycle takes effect. The duty cycle specified by the PWM
framework is internally converted to the 0-255 scale expected by the
hardware registers.
The legacy sysfs interface remains unaffected and operates in parallel.
No, I won't accept this. It has to be either or. A pwm channel modeled as pwm
subsystem channel must not be visible via hwmon attributes.
I didn't look in detail, but maybe my red line is a bit more lax. IMHO
it's not OK to be able to modify a setting that results from pushing
hwmon knobs using PWM operations or vice-versa. Switching between
exclusive use at runtime is IMHO ok.
Thanks,
Guenter