Re: 'Phys:' field for keyboards (and other input devices)

[Vojtech P. <vo...@su...>]

On Fri, Sep 27, 2002 at 09:34:31PM +1000, Brad Hards wrote:

> On Fri, 27 Sep 2002 21:12, Vojtech Pavlik wrote:
> > > If so, then what is EVIOCGUNIQ for?
> >
> > It's an identifier that a device may or may not have, and if there is
> > one, it must be universally (*) unique for this devices bus, vendor and
> > device id. Like USB storage UUID. It may be a serial number. Not that
> > many input devices have it, but the possibility is there.
> >
> > (*) - in whole universe, not just the system. Also it must not ever change.

> So it must be a property of the device, not a property of the system 
> configuration.

Exactly.

> And it is broken, at least on USB. We're reporting the same on both EVIOCGPHYS 
> and EVIOGUNIQ - the path.

Hmm, It doesn't seem so to me:

hid-core sets UNIQ to be

	usb_string(dev, dev->descriptor.iSerialNumber, hid->uniq, 64)

and PHYS to be

	usb_make_path(dev, buf, 64);
        snprintf(hid->phys, 64, "%s/input%d", buf, intf->altsetting[0].bInterfaceNumber);

Others usually don't set UNIQ and only set PHYS as they don't have an
unique identifier.

-- 
Vojtech Pavlik
SuSE Labs