ARCTIC Fan Controller Driver Expected To Land In Linux 7.2

A new driver expected to land in the upcoming Linux 7.2 kernel is the ARCTIC Fan Controller driver to allow fan speed monitoring and PWM controls for this upcoming ARCTIC product. Making this new driver all the more exciting is that it was worked on by ARCTIC directly compared to the typical workflow for such desktop/consumer hardware peripherals often being left up to the reverse-engineering, open-source community.

Back in March I wrote about ARCTIC Cooling publishing a fan controller driver for Linux. It's that driver that has now been queued into the Linux hardware monitoring "HWMON" subsystem's hwmon-next Git branch. With it in a "-next" Git branch now, it's then likely to be submitted for the Linux 7.2 merge window happening in mid-June.

The new driver is described by ARCTIC engineer Aureo Serrano de Souza as:

"Add hwmon driver for the ARCTIC Fan Controller, a USB HID device (VID 0x3904, PID 0xF001) with 10 fan channels. Exposes fan speed in RPM (read-only) and PWM duty cycle (0-255, read/write) via sysfs.

The device pushes IN reports at ~1 Hz containing RPM readings. PWM is set via OUT reports; the device applies the new duty cycle and sends back a 2-byte ACK (Report ID 0x02). The driver waits up to 1 s for the ACK using a completion. Measured device latency: max ~563 ms over 500 iterations. PWM control is manual-only: the device never changes duty cycle autonomously."

The C driver in its current form can be found via this commit in hwmon-next.

While ARCTIC does have a 10-port Case Fan Hub product currently, it doesn't have a USB interface and relies just on a single PWM signal for fan control across all ten fans. So it would appear this driver for the ARCTIC Fan Controller is for a new, upcoming product.

Great seeing ARCTIC working on this upstream Linux kernel support in advance of the product launch.