When using a combo touchscreen/tablet (with pen input), the kernel does not always provide an arbitration between the touch and the pen. This is the case for N-trig devices which are following the HID spec (found on the MS Surface 3 for instance). Libinput should disable at least the corresponding touch when the pen of the same group is in proximity. We could also be smart and disable only the touch points under the palm if the stylus reports the Tilt (which gives us an indication if the user is left handed or right handed).
Notes from a conversation today: use the touchscreen and tablet size to associate the two devices together, even if they're not the same physical device. e.g. the Lenovo Yoga has an elantech screen but a wacom tablet.
Closing this for now. We don't have access to those devices anymore and until someone actually complains that this is needed we don't need to keep the bug open.
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