title: linux inter driver communication
body: <p>on a raspberry pi I want to be able to use a rotary encoder as volume control.
  the best way I can see to do that would be using the rotary_encoder module to read the encoder, set it up as a relative axis (so would get +1 or -1 events) and then make a driver to interpret that to create volume up or volume down keypresses.</p>
  
  <p>however I'm struggling to get my head around interrupts and drivers, so my driver would have to register itself as able to provide EV_KEY events, which I think I've got handled, but I'm unsure how I can catch and act on events from the other driver?</p>
  
  <p>I figured I would have to poll the /dev/input/event object created by the other driver, but I can't seem to find a guide on how to do this?</p>
  
  <p>is this the best way to go? is there a way i can actually catch interrupts created by the other driver feeding events into the input system?</p>