Correct. "Apps use serial" hijacks the serial port away from the player application and allows other applications to open it. "notify=1" exposes the /proc/notify interface, and "suppress_notify=1" prevents the player from outputting track information to the port. Thinking about it, you probably don't need "suppress_notify=1" once "Apps use serial" is set - all the player serial output is being redirected to /dev/null anyway.