Simple ec script for controlling GPU and CPU fans for acer 3820T/3820TG/3820TZ/3820TGZ laptops

ec_3820t.py

#!/usr/bin/env python
# -*- coding: UTF-8 -*-

CONTROL_AUTO = 0x04
CONTROL_MANUAL = 0x14
FAN_MAX = 0x00
FAN_MIN = 0xFF

READY_TO_WRITE = 0x02
READY_TO_READ = 0x01

SET_WRITE = 0x81
SET_READ  = 0x80

class GPU:
    control = 0x93
    set = 0x94
    get = 0x95

class CPU:
    control = 0x96
    set = 0x97
    get = 0x98

import sys
import os
import time
import struct

if 'max' in sys.argv:
    m = CONTROL_MANUAL
    v = FAN_MAX
elif 'high' in sys.argv:
    m = CONTROL_MANUAL
    v = int(FAN_MIN*0.3)
elif 'medium' in sys.argv:
    m = CONTROL_MANUAL
    v = int(FAN_MIN*0.45)
elif 'low' in sys.argv:
    m = CONTROL_MANUAL
    v = int(FAN_MIN*0.6)
else:
    m = CONTROL_AUTO
    v = None

char_struct = struct.Struct('B')

def char(v):
    return char_struct.pack(v)

def unchar(v):
    return char_struct.unpack(v)[0]

def wait_write(f):
    os.lseek(f, 0x66, os.SEEK_SET)
    while unchar(os.read(f, 1)) & READY_TO_WRITE:
        time.sleep(0.01)
        os.lseek(f, 0x66, os.SEEK_SET)

def write_ec(f, pos, val):
    wait_write(f)
    os.lseek(f, 0x66, os.SEEK_SET)
    os.write(f, char(SET_WRITE))
    wait_write(f)
    os.lseek(f, 0x62, os.SEEK_SET)
    os.write(f, char(pos))
    wait_write(f)
    os.lseek(f, 0x62, os.SEEK_SET)
    os.write(f, char(val))

f = os.open('/dev/port', os.O_RDWR)
for device in (GPU, CPU):
    write_ec(f, device.control, m)
    if not v is None:
        write_ec(f, device.set, v)
os.close(f)