Video Output Switcher Control
  		~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  		2006 luming.yu@intel.com
  
  The output sysfs class driver provides an abstract video output layer that
  can be used to hook platform specific methods to enable/disable video output
  device through common sysfs interface. For example, on my IBM ThinkPad T42
  laptop, The ACPI video driver registered its output devices and read/write
  method for 'state' with output sysfs class. The user interface under sysfs is:
  
  linux:/sys/class/video_output # tree .
  .
  |-- CRT0
  |   |-- device -> ../../../devices/pci0000:00/0000:00:01.0
  |   |-- state
  |   |-- subsystem -> ../../../class/video_output
  |   `-- uevent
  |-- DVI0
  |   |-- device -> ../../../devices/pci0000:00/0000:00:01.0
  |   |-- state
  |   |-- subsystem -> ../../../class/video_output
  |   `-- uevent
  |-- LCD0
  |   |-- device -> ../../../devices/pci0000:00/0000:00:01.0
  |   |-- state
  |   |-- subsystem -> ../../../class/video_output
  |   `-- uevent
  `-- TV0
     |-- device -> ../../../devices/pci0000:00/0000:00:01.0
     |-- state
     |-- subsystem -> ../../../class/video_output
     `-- uevent