Comment 7 for bug 806032

From the previous findings, I've cooked a shellscript that uses acpi_call to determine the address and ID to write. It relies on the property that the DSDT of Clevo B7130 and Clevo W150HRM declare the base address in the \ASLB field. I've seen other machines hardcoding this value in their DSDT. In that case, look for the field that is possibly named IGDM and copy the address from the placeholder as shown below:

OperationRegion (IGDM, SystemMemory, ADDRESSHERE, 0x2000)

The DSDT can be retrieved using:
sudo apt-get install acpidump iasl
cd $(mktemp -d)
sudo acpidump > acpidump.txt
acpixtract acpidump.txt
iasl -d *.dat
grep IGDM DSDT.dat

Make the attachment executable and execute it with root:
chmod +x cadl_hack_brightness
sudo ./cadl_hack_brightness