Developing a Custom FreeBSD Driver for Power Button Support

A developer created a custom FreeBSD driver to fix a power button issue on an HP Laptop 15s after standard ACPI configurations failed to respond.

October 22, 2026, 06:00 AM·0 views

Photo: Хабр

The installation of FreeBSD 15.0 on an HP Laptop 15s was completed successfully, with the WiFi card and AMD graphics functioning immediately after setup. The system was configured with the Xorg X11 server and the Xfce4 desktop environment.

A technical issue arose when the power button failed to trigger a system shutdown, despite the shutdown command working correctly. Adjusting the system variable hw.acpi.power_button_state to S5 did not resolve the problem.

Kernel logs showed no ACPI messages during power button interaction, while the button functioned normally under Windows. This led to a two-week debugging process of the FreeBSD kernel and the development of a custom driver for the power button.