On Tue, 2014-09-09 at 12:53 -0400, 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.
Yes, that is the problem. I need to be more verbose. I am sorry.
These devices have a firmware bug. Actually several, but only one
is relevant here.
If they are suspended without remote wakeup they crash and
disconnect/reconnect as soon as they have data to deliver.
So we cannot suspend them without remote wakeup. Yet we would
very much like to power them down, for example when the laptop's
lid is closed.
I think the only way to do that is to tell usbcore to honour
needs_remote_wakeup for suspend but not power off by means
of an additional flag.
Regards
Oliver
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