In order to support very low power operation, the XO laptop uses a
secondary Display CONtroller, or DCON. This secondary controller
is present in the video pipeline between the primary display
controller (integrate into the processor or chipset) and the LCD
panel. It allows the main processor/display controller to be
completely powered off while still retaining an image on the display.
This controller is only available on OLPC platforms. Unless you have
one of these platforms, you will want to say 'N'.

source code:

drivers/staging/olpc_dcon/