output: Add output class document

Signed-off-by: Luming Yu <Luming.yu@intel.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>

diff --git a/Documentation/video-output.txt b/Documentation/video-output.txt
new file mode 100644 (file)
index 0000000..e517011
--- /dev/null
+++ b/Documentation/video-output.txt
@@ -0,0 +1,34 @@
+
+               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
+