Analyzing the DSDT DSL
By looking at the DSL file, we find the registers we are interested in:
Field (RAM, ByteAcc, Lock, Preserve)
{
[...]
Offset (0x93),
, 4,
FSH1, 1,
Offset (0x94),
FSW1, 8,
FAN1, 8,
, 4,
FSH2, 1,
Offset (0x97),
FSW2, 8,
FAN2, 8
[...]
}
Calculating the register addresses
- FSW1 = Offset(0x94) = 0x94 = 148
- FAN1 = Offset(0x94) + (8 / 8) = 0x95 = 149
- FSH1 = Offset(0x93) = 0x93 = 147
Finding the WriteRegister
We try to set the fan speed using FAN1 and FSW1:
sudo ec_probe write 148 0
sudo ec_probe write 148 50
sudo ec_probe write 148 100
sudo ec_probe write 149 0
sudo ec_probe write 149 50
sudo ec_probe write 149 100
None of these changed the fan speed, so it's likely that we need to set another register. Luckily, we have FSH1 which is one bit long.
We read the FSH1 register:
sudo ec_probe read 147
Output: 4 (0x04)
This (0x04) is the state where manual fan control is disabled
Field (RAM, ByteAcc, Lock, Preserve)
{
[...]
Offset (0x93),
, 4,
FSH1, 1,
}
We see that FSH1 starts at bit 4, so the desired value to set manual control is: 1 << 4 = 16
We add the original value 4 and 16 and get 20. This is probably our value for enabling manual fan control.
sudo ec_probe write 147 20
Write to the FSW1 register
sudo ec_probe write 148 0
sudo ec_probe write 148 50
sudo ec_probe write 148 100
sudo ec_probe write 148 150
sudo ec_probe write 148 200
sudo ec_probe write 148 250
The fan speed changed.
Result: FSW1 is our WriteRegister, FAN1 is the ReadRegister, FSH1 will be use in RegisterWriteConfigurations
Finding the MinSpeedValue / MaxSpeedValue
How MinSpeedValue and MaxSpeedValue are discovered is not described here.
See the description for the HP 620 configuration file: Finding the ReadRegister values and Finding the WriteRegister values.
Writing the configuration file
- 149 (FAN1) is the ReadRegister.
- 148 (FSW1) is the WriteRegister.
- 147 (FSH1) is used inside RegisterWriteConfigurations.
- 255 is the MinSpeedValue.
- 91 is the MaxSpeedValue.
- IndependentReadMinMaxValues is false, since FAN1 and FSW1 share the same range.
See the configuration file on GitHub