Suspend USB power to a laptop cooling pad when going to suspend mode

Question

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:

• http://stackoverflow.com/questions/4702216/controlling-a-usb-power-supply-on-off-with-linux

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

• http://www.mjmwired.net/kernel/Documentation/usb/power-management.txt

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?

Answer 1

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