Re: [PATCH] Input: Add ioctl to block suspend while event queue is not empty.

On Thu, Feb 16, 2012 at 11:31:06PM +0100, Rafael J. Wysocki wrote:

Can you actually select what keys may wake up the system from sleep
(I mean "real sleep", when the whole system is entirely off except for wakeup
devices)?

Yes, that's often possible.  In suspend mode you can get a two stage
process where the wakeup itself is triggered by simply looking for any
electrical activity on a set of pins.  This generates a wakeup and an
interrupt for the keypad which then powers up the actual keypad circuit
and looks to see what the keypress was.  The Samsung keypad driver in
mainline does this in runtime PM, while no key is pressed the keypad
controller is in suspend mode.