You need to have the kernel headers (e.g. linux-header-generic) installed for the kernel you're compiling for. You also need the build tools (build-essential or similar).
- git clone git://github.com/patjak/mba6x_bl
- cd mba6x_bl
- make
- sudo make install
- sudo depmod -a
Note: You no longer need to specify mba6x_bl as your backlight device in /etc/X11/xorg.conf. This is now handled automatically by promoting the driver above the ACPI backlight interface.
At this point you can load the module
sudo modprobe mba6x_bl
Then restart X (usually log in / log out will do the trick). The module should automatically load on next boot on any MacBook Air 6,x.
You can either follow the long route https://wiki.kubuntu.org/Kernel/Dev/DKMSPackaging, or
download a pre-made .deb file from http://miek.nl/downloads/2014/mba6xbl-dkms_0.0.3_all.deb,
which can be installed with dpkg -i.
https://help.ubuntu.com/community/MacBookAir6-2/Trusty#Backlight
An Arch Linux prepared package can be found at https://aur.archlinux.org/packages/mba6x_bl-dkms/