The midi(4) driver supports FIOASYNC, but seems to set the signal
recipient unconditionally to p (the struct proc * argument to
midiioctl) - it doesn't do anything special with FIOSETOWN.

Is this a bug, or could FIOSETOWN be handled somewhere in a common
calling layer so the p passed as argument is the right one? I haven't
chased it down in the code yet.

-Chap