Apple Gmux Driver

modulename: apple-gmux.ko

configname: CONFIG_APPLE_GMUX

Linux Kernel Configuration
└─>Device Drivers
└─>X86 Platform Specific Device Drivers
└─>PCI support
└─>Plug and Play support
└─>Apple Gmux Driver
In linux kernel since version 3.1 (release Date: 2011-10-24)  
This driver provides support for the gmux device found on many
Apple laptops, which controls the display mux for the hybrid
graphics as well as the backlight. Currently only backlight
control is supported by the driver.

source code:
drivers/platform/x86/apple-gmux.c