Re: USB: add check to detect host controller hardware removal

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On 2023-11-03 16:42:18 [-0400], Alan Stern wrote:
> > I see. Don't over complicate or "correct" things here. What should work
> > is that the removal callback can be called at any time and things
> > continue work. That means it will purge all queues, cancel all requests,
> > timers, whatever and free all resources associated with the driver/
> > device.
> 
> The driver _does_ work under those circumstances -- provided the
> hardware is still present and accessible.

In that case I don't see a problem.

> > If it comes to PCI-hotplug you have to have a so called PCI-hotplug
> > slot. This "slot" will let the OS know if the hardware has been removed
> > or added. If you don't have such a thing you have to maintain the state
> > yourself by using the "remove" and "rescan" sysfs files of the PCI slot.
> > 
> > I'm not aware of any requirement for a PCI-driver to check if its device
> > has been removed.
> 
> That's the problem: The driver doesn't really support PCI-hotplug.
> The code that Meng Li wants to change was sort of a half-baked way to
> add such support.

This sounds half-baked. Just remove the device from sysfs and then
physically plug the card. It is going to end in mess if every driver
gets some "hotplug" support.

> Alan Stern

Sebastian