pub fn try_take_audio_lease() -> Option<Cd>Expand description
Take the drive for audio only if it is free right now, in one step: the
controller token if the lease was granted, None if a read is in flight.
Nothing is left pending and the read is not aborted, so a read submitted
afterwards is never parked behind a lease granted later. See
Engine::try_audio_lease; end the lease with release_audio_lease.