Add a debugfs interface for sending commands to the OLPC Embedded Controller (EC) and reading the responses. The EC provides functionality for machine identification, battery and AC control, wakeup control, etc. Having a debugfs interface available is useful for EC development and debugging. Based on code by Paul Fox (who also approves of the end result). Signed-off-by: Daniel Drake <dsd@laptop.org> Acked-by: Paul Fox <pgf@laptop.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andres Salomon <dilinger@queued.net> Link: http://lkml.kernel.org/r/20120327150740.667D09D401E@zog.reactivated.net Signed-off-by: Ingo Molnar <mingo@kernel.org>