$:/sys/bus/usb/devices/6-1/power$ echo "0" > /sys/bus/usb/devices/6-0:1.0/power/state
bash: /sys/bus/usb/devices/6-0:1.0/power/state: Permission denied
Even with all combinations of sudo. It seems this attribute is read only, I have not seen this "permission denied" anywhere else.
Discussion continues in other thread, the one I started.
I am not the original poster, and I was trying to use these commands to do something slightly different- power down usb ports, that have various peripherals attached. This turned out to be impossible to do.