qemu-stormcrow should be launched as a daemon first. `cargo run` in a terminal, or write a systemd service, or spawn it in the background from a script, or whatever. It does not self-daemonize.
-A USB device with a (=Vendor ID=, =Product ID=) pair is registered for a running libvirt VM via D-Bus:
+A USB device with a (`Vendor ID`, `Product ID`) pair is registered for a running libvirt VM via D-Bus:
$ dbus-send --type=method_call --print-reply --dest=com.stormcrow.device /device com.stormcrow.device.Add string:<VM> string:<VID> string:<PID>