Definitely:

- Find an actual PS/2 mouse, plug it into the adaptor, make sure
  the mouse port still works while marsond is running. It *should*
  since it's a separate device under /dev/input, but it's better to
  know than to assume. I have an old Kensington PS/2 trackball
  in a box somewhere...

Maybe:

- If anyone ever finds another adaptor that has the Enter key
  issue, with a different USB vendor and product ID, add another
  udev rule for it.

- Actual realtime scheduling (maybe). sched(7). Not sure it's
  needed (nice -20 seems OK even while compiling mame with -j5), and it
  might interfere with stuff like JACK. Plus, it would bloat the
  daemon (have to link with -lrt).

- Use a log file instead of stderr, so we can have error/warning messages
  after detaching from the tty. Probably not going to need this,
  users can use -vf for troubleshooting.

- Options to set the virtual device name and vendor/product IDs. Would
  anyone ever need this? KISS principle says wait & see.