Verify that bus sockets are present.
# ls /sys/kernel/debug/usbmon
-1s 1t 1u 2s 2t 2u 3s 3t 3u 4s 4t 4u
+0s 0t 0u 1s 1t 1u 2s 2t 2u 3s 3t 3u 4s 4t 4u
#
+Now you can choose to either use the sockets numbered '0' (to capture packets on
+all buses), and skip to step #3, or find the bus used by your device with step #2.
+
2. Find which bus connects to the desired device
Run "cat /proc/bus/usb/devices", and find the T-line which corresponds to
# cat /sys/kernel/debug/usbmon/3u > /tmp/1.mon.out
+to listen on a single bus, otherwise, to listen on all buses, type:
+
+# cat /sys/kernel/debug/usbmon/0u > /tmp/1.mon.out
+
This process will be reading until killed. Naturally, the output can be
redirected to a desirable location. This is preferred, because it is going
to be quite long.