Querying USB device's bInterfaceNumber

Ping pinglinux at gmail.com
Tue Nov 3 14:35:04 PST 2009

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 :).

> > Once it comes to xorg, the device is mapped onto two logical ports.  I
> need
> > a way to tell which logical port is for touch and which one is for
> > penabled.
> Can't you get that from the different descriptors?

I am testing a way to resolve this issue.  Hopefully it doesn't need to make
a change either in the kernel or in X server.

Thank you both for discussing the problem with me.  That is the best help I

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