users of libinput need some sort of mechanism to tell whether a device is a mouse, touchpad, trackball, etc., in addition to the current capability sets. the need for this is primarily triggered by the GUI config tools to categorise device configuration (e.g. GNOME has a mouse/touchpad configuration tool split) main question here is whether a device can have a single tag only, or whether we allow for multiple tags for mixed devices (which would allow defining tags a lot narrower). If multiple tags are allowed, then that could also be used to tag a device as e.g. intern/external
Does libinput "split" kernel devices? For example, would an external ThinkPad keyboard, or combined keyboard/touchpad device be one or two libinput devices? If it doesn't split them, a bitfield would be better.
no, libinput just takes the kernel device as it is and sets the matching capabilities. lesson learned from X where splitting devices caused a couple of drawbacks, so the capabilities-based approach is much better.
Closing this as WONTFIX. Every situation we have come up with so far was better solved without this, specifically by checking what sets of configuration options or keys/buttons are available. We also provide a handle to the udev device which let's the caller query information about it and then make decisions based on the context needed. libinput sits too low and has too little context to make the right decision here, any tagging system is likely going to fall short and require the caller to have a separate tagging system on top of it.
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