Re: [rft]power management for usbtouch

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Mon, Jun 30, 2008 at 12:16:13PM -0400, Alan Stern wrote:
> On Mon, 30 Jun 2008, Dmitry Torokhov wrote:
> 
> > > My feeling is that we will leave manual suspension in the kernel.  The
> > > code passed to the USB driver's suspend method will be changed so that
> > > the method can tell whether it is being called for a system sleep vs.
> > > an autosuspend vs. a manual suspend.
> > > 
> > 
> > Ok, I see... So what does a device do when it is suspended and a
> > request comes in? Does it automatically resume and service the request
> > (and potentially goes back to sleep)? Does it queue the request for
> > later? Ignore it? Is it a system-wide policy or up to the device
> > [class]?
> 
> What sort of request do you mean?  If a device is suspended, it _can't_ 
> receive any data (requests or otherwise) over the USB bus.
> 
> If a device receives data over some other channel (like a mouse getting
> a button click) while it is suspended, its behavior depends on the
> settings at the time it was suspended.  If remote wakeup was disabled
> then the device does essentially nothing (maybe it remembers the data
> for later, maybe not).  If remote wakeup was enabled then the device
> should send a wakeup request to the host.
> 

I was talking about system-initiated requests... Setting LED on a keyboard,
setting rate on a mouse, uploading a force-feedback effect, writing a
sector on a disk, etc...

-- 
Dmitry