title: Can't power-down USB device
body: <p>Here's my problem:
  <code>
  mint power # uname -a
  Linux mint 3.13.0-24-generic #46-Ubuntu SMP Thu Apr 10 19:11:08 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
  mint power # pwd
  /sys/bus/usb/devices/usb5/5-2/power
  mint power # cat autosuspend autosuspend_delay_ms control level persist 
  1
  1000
  auto
  auto
  1
  mint power # echo on &gt;level
  mint power # echo off &gt;level
  bash: echo: write error: Invalid argument
  mint power # echo suspend &gt;level
  bash: echo: write error: Invalid argument
  mint power #
  </code></p>
  
  <p>Why can't I power-off the USB device? Clearly the hardware has the capability!</p>