dell-fanctl

Adaptive fan controller for Dell laptops. Automatically switches between quiet and gaming fan curves based on CPU load and temperature — no manual intervention needed.

Uses the dell_smm_hwmon kernel module for direct PWM fan control. Tested on the Latitude 5400 but should work on any Dell laptop that exposes pwm1 via dell_smm_hwmon.

How it works

dell-fanctl monitors CPU utilization by reading /proc/stat every 3 seconds and reads CPU package temperature from coretemp. It maintains two PWM curves — quiet and gaming — and interpolates fan speed based on the active curve and current temperature.

Hysteresis prevents thrashing:

• Gaming mode engages after 12 seconds of sustained >55% CPU
• Quiet mode re-engages after 30 seconds of sustained <25% CPU
• Counter decay (not hard reset) absorbs transient spikes and dips

The asymmetry is deliberate — ramp up fast to protect thermals, ramp down slow to survive loading screens.

Temperature-driven PWM:

• Quiet curve: fan off below 50C, ramps to full at 85C
• Gaming curve: fan starts at 40C, full blast at 72C

On shutdown, PWM is set to 0 (BIOS auto control restored).

Components

File	Purpose
dell-fanctl	Adaptive fan daemon (Python 3, zero deps)
dell-fanctl-tray	System tray applet (GTK3 + AppIndicator3)

The tray applet shows a purple Q in quiet mode and a blue G in gaming mode. Right-click for manual override — forced profile sticks until CPU load naturally triggers the opposite transition.

Requirements

• A Dell laptop with dell_smm_hwmon kernel module and pwm1 control
• Python 3.10+
• python3-gobject + libappindicator-gtk3 (for tray applet only)

Install

git clone <this-repo>
cd dell-fanctl
sudo ./install.sh
sudo systemctl start dell-fanctl

The installer:

1. Copies binaries to /usr/local/bin/
2. Configures dell_smm_hwmon with restricted=0 force=1 via modprobe
3. Installs and enables the systemd service
4. Sets up tray applet autostart

Immutable distros (Bazzite, Silverblue, etc.)

All files go to /usr/local/ and /etc/, which persist across updates. No packages to layer — the daemon is pure Python stdlib and the tray uses pre-installed GTK3 bindings.

PWM Curves

Edit the CURVE_QUIET and CURVE_GAMING lists in /usr/local/bin/dell-fanctl to adjust the temperature-to-PWM mapping. Each entry is (temp_celsius, pwm_value) with linear interpolation between points.

Note: Most Dell laptops map PWM values to a few discrete fan speed steps rather than linear RPM. Test with different values to find the effective steps for your model.

Checking your Dell's compatibility

# Load the module
sudo modprobe dell_smm_hwmon restricted=0 force=1

# Find the hwmon device
for d in /sys/class/hwmon/hwmon*; do
    [ "$(cat $d/name 2>/dev/null)" = "dell_smm" ] && echo "$d" && break
done

# Check for PWM control
ls /sys/class/hwmon/hwmon*/pwm1 2>/dev/null

# Test a write (sets fan to ~50%)
echo 128 | sudo tee /sys/class/hwmon/hwmon*/pwm1

# Restore BIOS control
echo 0 | sudo tee /sys/class/hwmon/hwmon*/pwm1

Uninstall

sudo ./uninstall.sh

License

MIT