usb suspend (was Re: So, what's the status on the recent patches here?)

[Pavel Machek <pavel@ucw.cz>]

Hi!

> > > The idea of the patches is that they will autosuspend a USB hub when it
> > > has no active (i.e., unsuspended) children, and autosuspending a root hub
> > > stops the USB controller from doing DMA.  However, non-hub devices are not
> > > yet automatically suspended, so you will have to suspend the fingerprint
> > > scanner by hand.
> > 
> > That is okay, I can do that. It saves 2 hours of battery life on my
> > machine...
> 
> Come to think of it, you don't need the autosuspend patches to turn these 
> devices off.  You can do it right now with your existing kernel, although 
> it's a little easier with -mm.  (The reason is that -mm contains a 
> development patch which ties a USB device's interfaces to the device 
> itself; suspending the device will automatically suspend all its 
> interfaces, and likewise resuming the device will automatically resume all 
> its interfaces.  With a vanilla kernel you must manually suspend the 
> interfaces before you can suspend the device and manually resume them 
> after resuming the device.)
> 
> Anyway, you can use the deprecated 
> 
> 	echo -n 2 >/sys/devices/.../power/state
> 
> mechanism to suspend all the USB interfaces, devices, and controllers you 
> want -- provided you work your way up from the bottom of the device tree.  
> The autosuspend patch just makes it simpler, since it takes care of 
> suspending and resuming all the hubs for you.

Thanks! That works great and gets my power consumption into reasonable
range.. plus allows fan to actually stop.
									Pavel

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