[ltp] power to the usb port while laptop is off

[Henrique de Moraes Holschuh]

On Sun, 03 May 2009, Volker Krueger wrote:
> I have the following question: My X200s seems to have a bios setting  
> which keeps the usb port powered even if the laptop is in a low-power  
> state or switched off.

This can happen, yes.  And Linux is currently _broken_ in that it
cannot tell the thinkpad to power down the USB port using the ACPI
power resources provided by IBM and Lenovo for a *LONG* time now.  It
is being worked on (I hope), but it is not that easy to fix due to
other kernel concerns.

But the above only applies to power to the USB port during
suspend-to-RAM.

> Is this understanding correct?

You'll have to test.  It might make sense to have a setting to keep
the USB port powered up during S3 and S4 sleep, but not shutdown.
Powered USB ports after shutdown are a BIOS or EC firmware bug.

> I keep having problems with my laptop: I think I remember that before my  
> motherboard got changed, the usb port was indeed powered. However now,  
> after the change, the usb port is only powered if the laptop is running,  
> no matter how the bios is set.

System board (aka planar card, aka motherboard) change implies a BIOS
update.  Check if you don't need to update yet again.  That said,
check if the BIOS option is not controlling what happens while the
laptop is sleeping.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh