Usage: int ddu_start() , ddu_stop()
Returns: 0 if good status, -1 if bad status.
This routine requires that the process is attached to a fifo
(i.e. called ddu_init). The thus created fifo is in an idle
state and has to be actived before events can be obtained.
The fifo can be made idle by calling ddu_stop().
Switching back and forth between ddu_start(), ddu_stop()
allows a process to become active/inactive within the DD system
without detaching.
NOTE:
While the fifo is NOT active, no events can be retrieved. The
INPUT fifo is always active.