[PATCH libinput 0/3] Restore capability events

[Peter Hutterer]

Short summary: we had capability events in libinput which worked essentially
like wayland's capability events. They were kicked out (by me) because by
the time we get a device from the kernel it is static and won't change
anymore. So capabilities make sense on the protocol where pointers may get
added or removed, but they don't in libinput because the devices we have are
static.

Fast forward to trying to add tablet support. One of the plans we have is to
provide merged devices, i.e. one struct libinput_device for a logical
device, even if that device is exposed as multiple evdev device nodes. This
would affect the tablets that can have up to three nodes: one for the tools,
one for the pad and one for touch.

To enable this we need a device be able to add/remove capabilities since we
need to initialize a device based on the first event node and then add the
interfaces when the second event node is seen by libinput.

Cheers,
  Peter