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When I suspend the laptop, the USB devices are left on. I don't mind this in general, however I'd like to be able to turn off the cooling pad under it. I tried the things outlined in the following:

however this doesn't work anymore in Linux 3.0.0. I read the kernel docs:

and tried this (also outlined here - http://www.thinkwiki.org/wiki/How_to_reduce_power_consumption):

for i in /sys/bus/usb/devices/*/power/autosuspend; do echo 1|sudo tee $i; done 
for i in /sys/bus/usb/devices/*/power/level; do echo auto|sudo tee $i; done

I can confirm this works properly for some devices - e.g. my USB keyboard auto-suspends as expected. However, some devices do not - e.g. my USB touchpad, USB hub it's connected to and the cooler are left with power.

My questions:

  • Why are devices behaving differently? Does this mean that it's up to each of the devices to decide whether to suspend?
  • Is there a way to determine whether a device will go into suspend mode?
  • Finally, is there a way to force a device to power down?
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1 Answer

The reason for that can be hardware related and nothing to do with software.

Some motherboards now a days have an option to allow some of the USB ports to be always powered no matter the state of the computer: if its plugged in / batery connected, there is power on that USB connector.

That feature can be easily identifiable by the different symbol on the USB port and some computer makers have also an option on the BIOS to enable/disable that feature

enter image description here

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Thanks Bruno. I don't think I remember seeing such an option - it's one of those 3-option laptop BIOSes, but I can definitively check that. However, assuming there's no BIOS option, is there a way to determine what is the hard-wired default and / or make it power down? –  icyrock.com Jan 30 '12 at 0:24
    
You can check the symbol of the USB plug, normally powered USB ports have a small lightning symbol on the port it self, sort of like this. –  Bruno Pereira Jan 30 '12 at 0:32
    
Interesting! Is this true for laptops and desktops? It seems none of my ports are like this. Again, it's a laptop, so it might just be that it was a space constraint. On the other hand, I mentioned in my post that I can actually power down my keyboard, which is on the same (external) USB hub as my touchpad. I could not power down either the touchpad or the USB hub itself. –  icyrock.com Jan 30 '12 at 0:38
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