Represents the state of an input mt slot
struct input_mt_slot {
  int abs[ABS_MT_LAST - ABS_MT_FIRST + 1];
  unsigned int frame;
  unsigned int key;
};
        abs[ABS_MT_LAST - ABS_MT_FIRST + 1]
holds current values of ABS_MT axes for this slot
frame
last frame at which input_mt_report_slot_state was called
key
optional driver designation of this slot