Querying USB device's bInterfaceNumber

Greg KH greg at kroah.com
Tue Nov 3 14:42:03 PST 2009

On Tue, Nov 03, 2009 at 02:35:04PM -0800, Ping wrote:
> On Tue, Nov 3, 2009 at 2:08 PM, Greg KH <greg at kroah.com> wrote:
> > On Tue, Nov 03, 2009 at 12:19:54PM -0800, Ping wrote:
> > > These questions make me feel the kernel driver may need some work.
> >  Anyway,
> > > let me share what I have now before we can figure out a better solution:
> > >
> > > Wacom supports both penabled and touch digitizers.  The older tablets
> > > doesn't have touch.  So, there is no problem there.  The newer tablets
> > have
> > > both pen and touch through the same physical USB port. They are definded
> > in
> > > separate HID descriptors with the same vendor id and product id.  So, for
> > > kernel, I think, it is one physical device.
> >
> > Yes, but it should show up as 2 different hid devices, right?
> >
> Will that help?  Wacom devices are not processed by HID.  We told hid-core.c
> to ignore all Wacom devices. That is why I said "I am in control" (I know I
> am not in control. I am most likely in the middle of nowhere :).

Heh, ah, that makes more sense now.

So you need to intrepret the hid report yourself in your driver and
export 2 devices to userspace which your xorg driver should then be able
to determine which is which by some type of identifier in them (not the
interface number, use the type of the device somehow.)


greg k-h

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