Re: [RFC]Johan's patch for touchscreens and port power off

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On Tue, 9 Sep 2014, Alan Stern wrote:

> On Tue, 9 Sep 2014, Oliver Neukum wrote:
> 
> > On Tue, 2014-09-09 at 11:23 -0400, Alan Stern wrote:
> > > On Tue, 9 Sep 2014, Oliver Neukum wrote:
> > > 
> > > > Hi,
> > > > 
> > > > Johan's patch means that for the affected touchscreen the port
> > > > can never be powered off. It seems to me that this needs a special
> > > > flag. What do you think?
> > > 
> > > Why can't the port be powered off?
> > 
> > needs_remote_wakeup is permanently set.
> 
> That's okay, then.  We never power-down a port if the attached device 
> is enabled for remote wakeup.  See the last few lines in 
> usb_port_suspend() in hub.c.

Sorry, I misunderstood.  You meant that the port can't be powered off 
because remote wakeup is enabled, but the driver doesn't really need 
remote wakeup even though it sets the needs_remote_wakeup flag.

In other words, you want to power-off the port, but are prevented from
doing so by the fact that the device disconnects itself from the bus if 
it is suspended without remote wakeup.

My feeling is that this is not worth the effort.  Leave the port 
powered on.  Or let the device disconnect itself and then power-off the 
port.

Alan Stern

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