Comment # 14 on bug 967490 from Oliver Neukum

(In reply to Thomas Mitterfellner from comment #13)
> Unfortunately, it will take a little while until I can test this on the
> machine itself, BUT: I'm pretty sure
> /sys/bus/usb/devices/$DEVICE/power/level does not exist as you can see from
> the output of
> 
> for i in /sys/bus/usb/devices/1-6:1.0/power/* ; do echo -n "$i: " ; cat $i ;
> done
> 
> I posted above, i.e. the only files residing there are:
> 
> async, runtime_active_kids, runtime_enabled, runtime_status, and
> runtime_usage.

You are looking into the wrong directory. Possibly you are looking at the
device, not at the interface.

> That said, I could of course try the two echo commands. OTOH, I just read
> here https://www.kernel.org/doc/Documentation/usb/power-management.txt that
> power/level is deprecated since kernel 2.6.35, so I should probably try this
> with power/control?

It doesn't matter which file you use. Please test.