Re: [RFC PATCH 2/4] rust: usb: add usb host interface and endpoint abstractions

[Alan Stern]

On Tue, Jul 14, 2026 at 07:57:21PM +0200, Oliver Neukum wrote:
> On 14.07.26 18:26, Alan Stern wrote:
> > At first I thought that we ought to have such a guarantee.  But in fact
> > we don't, because the user can at any time write to a USB device's
> > bConfigurationValue sysfs attribute even if the device isn't bound to a
> > driver.  This can create interfaces which may then be bound to drivers.
> > I just tried it and it worked.
> > 
> > This wasn't the original intent, but I don't see any good reason to
> > prevent people from doing it.
> 
> I hardly dare ask, but what happens if you unplug the device?

Exactly what you would expect: The interface driver is unbound and the 
device and interface disappear.  This line shows up in the dmesg log (I 
didn't have dynamic debugging turned on):

[406254.947595] usb 3-1: USB disconnect, device number 15

You can try it for yourself; it's an easy experiment to do.  I used a 
USB mouse for the test.

Alan Stern