(Specifically, the bitmask reported by /proc/bus/inputs/devices corresponds to BTN_STYLUS2 | BTN_STYLUS | BTN_TOOL_FINGER | BTN_TOOL_AIRBRUSH | BTN_TOOL_BRUSH | BTN_TOOL_RUBBER | BTN_DIGI | BTN_EXTRA | BTN_SIDE | BTN_MIDDLE | BTN_RIGHT | BTN_LEFT)
[BTN_TOOL_PEN also being an alias for BTN_DIGI, and BTN_LEFT for BTN_MOUSE]
(Specifically, the bitmask reported by /proc/bus/ inputs/ devices corresponds to BTN_STYLUS2 | BTN_STYLUS | BTN_TOOL_FINGER | BTN_TOOL_AIRBRUSH | BTN_TOOL_BRUSH | BTN_TOOL_RUBBER | BTN_DIGI | BTN_EXTRA | BTN_SIDE | BTN_MIDDLE | BTN_RIGHT | BTN_LEFT)
[BTN_TOOL_PEN also being an alias for BTN_DIGI, and BTN_LEFT for BTN_MOUSE]