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