Track number of current device

Hi,
this seems easy but I can't find a solution:

How do you ask the lom to give me the track number (or name) where a m4l device currently sits in? I don't want this to be done with the "view selected_track" but in the background.

For example: I would have a device that only prints the track number on startup. I have 8 tracks and drag the device on each of them. On startup it would say:

print: hi i am track 1
print: hi i am track 2
...
print: hi i am track n

much obliged for any help
stephen