Simple fan controller in Python using Linux hwmon sensors and liquidctl

pyfanctrl.py

#!/usr/bin/env python

import sys
import json
import time
import subprocess
import statistics

"""
    { "sensor_low": 35, "sensor_high": 40, "fan_level": 30 },
    { "sensor_low": 39, "sensor_high": 43, "fan_level": 40 },
    { "sensor_low": 42, "sensor_high": 47, "fan_level": 50 },
    { "sensor_low": 46, "sensor_high": 50, "fan_level": 80 },
    { "sensor_low": 49, "sensor_high": 52, "fan_level": 100 },
"""

KMODULE = "it87"
CHIP = "it8686-isa-0a60"
SENSOR = "EC_TEMP"
THRESHOLDS = [
    { "sensor_low": 35, "sensor_high": 40, "fan_level": 30 },
    { "sensor_low": 39, "sensor_high": 43, "fan_level": 75 },
    { "sensor_low": 42, "sensor_high": 52, "fan_level": 100 },
]
HISTORY = list()
ROLLING_COUNT=10
FAN_LEVEL = THRESHOLDS[0]["fan_level"]
SAMPLING_FREQUENCY = 6
GAMEMODE_MAX = True


def gamemode_active():
    p = subprocess.run(['ps', 'ax'], stdout=subprocess.PIPE)
    return b"gamemoderun" in p.stdout


def get_sensor_data():
    p = subprocess.run(['sensors', '-j', CHIP], stdout=subprocess.PIPE)
    return json.loads(p.stdout)


def set_fan_level(level):
    print(f"Set fan level to {level}")
    subprocess.run(['liquidctl', 'set', 'fans', 'speed', str(level)])


def get_sensor_sample():
    sensor_data = get_sensor_data()[CHIP][SENSOR]
    for key, value in sensor_data.items():
        if key.endswith("_input"):
            return value

    raise RuntimeError(f"Unable to locate sensor data value for sensor {SENSOR} on chip {CHIP}")

print(f"Loading kernel module '{KMODULE}'")
subprocess.run(['modprobe', KMODULE])

set_fan_level(THRESHOLDS[0]["fan_level"])

while True:
    # Flush stdout stream for more responsive logging
    sys.stdout.flush()

    # Sleep X seconds between samplings
    time.sleep(SAMPLING_FREQUENCY)

    # If enabled, set fans to max when gamemode is active
    if GAMEMODE_MAX and gamemode_active():
        if FAN_LEVEL != 100:
            print("Setting fans to max while gamemode is active")
            set_fan_level(FAN_LEVEL := 100)
        continue            

    # Read the current value and record it
    sensor_value = get_sensor_sample()
    HISTORY.append(sensor_value)

    # Make sure we keep only as many data points as we care to average
    if len(HISTORY) > ROLLING_COUNT:
        HISTORY.pop(0)
    else:
        continue

    # Calculate the rolling average
    rolling_average = statistics.mean(HISTORY)
    level_up = False

    # Decide if we need to change the fan level
    for threshold in THRESHOLDS:
        if level_up or (FAN_LEVEL > threshold["fan_level"] and rolling_average < threshold["sensor_low"]):
            FAN_LEVEL = threshold["fan_level"]
            set_fan_level(FAN_LEVEL)
            print(f"Fan level: {FAN_LEVEL}")
            print(f"Sensor rolling avg: {rolling_average}")
            break
        elif FAN_LEVEL == threshold["fan_level"] and rolling_average > threshold["sensor_high"]:
            level_up = True

I wrote this for my own setup. The pump and 4 fans are plugged into a Corsair Commander Core XT, which liquidctl can support on Linux. I have a water temperature sensor at the outlet of the pump. That is the sensor being measured to make fan/pump speed decisions.

If it's useful to someone else, cool. Otherwise, this is just out here to be archived in case I reinstall and forget to copy it off my system.