qubes-core-admin-linux/udev/udev-qubes-usb.rules

# Expose all USB devices (except block) via xenstore

# Handle only USB devices
SUBSYSTEM!="usb", GOTO="qubes_usb_end"

ACTION=="add", IMPORT{program}="/usr/lib/qubes/udev-usb-add-change"
ACTION=="change", IMPORT{program}="/usr/lib/qubes/udev-usb-add-change"
ACTION=="remove", RUN+="/usr/lib/qubes/udev-usb-remove"

LABEL="qubes_usb_end"