Some tablets have BTN_TOOL_PEN (and others) but never actually send the events. We should emulate those internally when we see BTN_TOUCH or a nonzero pressure, as well as enabling the proximity out quirk automatically on those devices.
has evemu recordings for an aiptek tablet that doesn't send those tool events.
See series starting here:
Author: Peter Hutterer <firstname.lastname@example.org>
Date: Tue Feb 6 14:22:01 2018 +1000
tablet: fake a BTN_TOOL_PEN on the first event if needed