On Wed, Aug 30, 2017 at 08:36:23AM +0200, Lukas Wunner wrote: > On Tue, Aug 29, 2017 at 05:51:38PM +0200, Greg Kroah-Hartman wrote: > > On Tue, Aug 29, 2017 at 05:34:56PM +0200, Lukas Wunner wrote: > > > On Tue, Aug 29, 2017 at 04:47:25PM +0200, Greg Kroah-Hartman wrote: > > > > On Tue, Aug 29, 2017 at 03:38:52PM +0200, Lukas Wunner wrote: > > > Is 0xffffffff not a valid value to be stored in and read from mmio space? > > > > For a specific register, doubtful > > Well, "doubtful" means you don't know for sure. > > It's fine to check for "all ones" as a heuristic if that's not a valid > value for the register read, however a hotplug notification is a > *definitive* indication the hardware is gone. > > I you seem to prefer forgoing a *definitive* indication for a mere > heuristic, that doesn't make sense from my point of view. I still don't know what you are arguing about here. The _driver_ knows if a specific read allows all ones as a valid return value. If it isn't, then the driver knows the device is now gone. It's that simple, don't do that type of check if all ones is a valid read. And that's not what is happening here anyway, so again, what is this discussion about? Unless there's something specific we can do here for the xhci driver, I think this thread is dead until someone determines what is going wrong with the hardware the original reporter posted about. greg k-h
