原型
/**
* input_mt_init_slots() - initialize MT input slots
* @dev: input device supporting MT events and finger tracking
* @num_slots: number of slots used by the device
*
* This function allocates all necessary memory for MT slot handling
* in the input device, prepares the ABS_MT_SLOT and
* ABS_MT_TRACKING_ID events for use and sets up appropriate buffers.
* May be called repeatedly. Returns -EINVAL if attempting to
* reinitialize with a different number of slots.
*/
int input_mt_init_slots(struct input_dev *dev, unsigned int num_slots);