Querying USB device's bInterfaceNumber

Greg KH greg at kroah.com
Tue Nov 3 14:08:10 PST 2009

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?

> 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?


greg k-h

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