On Tue, Sep 09, 2014 at 02:33:42PM -0400, Alan Stern wrote: > On Tue, 9 Sep 2014, Oliver Neukum wrote: > > > On Tue, 2014-09-09 at 13:25 -0400, Alan Stern wrote: > > > 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. > > > > It would reconnect. For a mouse I wouldn't bother, but here we are > > dealing with a laptop's touchscreen. We'd break D3cold for the HC > > permanently and totally. > > Only runtime D3cold would be affected. System suspend would still be > able to use D3cold. > > Also, if the user doesn't care about the touchscreen, you could unbind > it from the driver. Then the kernel would suspend it and power-off the > port before the device could reconnect. Turns out that the hub that the Elan touchscreen is connected to in this particular Samsung laptop (ATIV Book 9 Plus) does not even support port-power switching. Johan -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
