> That's not true. USB devices can be identified uniquely by physical
> path -- see "lsusb -t". For a wired down device, you can figure out
> which one it is as long as you always solder it to the same spot.
That's the problem. It is not always soldered at the same spot,
if at all, from one board to another similar board. Some parts of
the kernel have no choice but to know differences between such similar
boards already (such as what GPIO is connected to what LED, or what
key, or what IRQ signal, etc). Duplicating part of that knowledge in
user space would increase maintenance costs, and there is no good way
to identify such boards from user space in the first place.