drivers/input/input-mt.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Input Multitouch Library
  *
  * Copyright (c) 2008-2010 Henrik Rydberg
  */

 #include <linux/input/mt.h>
 #include <linux/export.h>
 #include <linux/slab.h>

 #define TRKID_SGN	((TRKID_MAX + 1) >> 1)

 static void copy_abs(struct input_dev *dev, unsigned int dst, unsigned int src)
 {
 	if (dev->absinfo && test_bit(src, dev->absbit)) {
 		dev->absinfo[dst] = dev->absinfo[src];
 		dev->absinfo[dst].fuzz = 0;
 		__set_bit(dst, dev->absbit);
 	}
 }

 /**
  * 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
  * @flags: mt tasks to handle in core
  *
  * 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.
  * Depending on the flags set, it also performs pointer emulation and
  * frame synchronization.
  *
  * 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,
 			unsigned int flags)
 {
 	struct input_mt *mt = dev->mt;
 	int i;

 	if (!num_slots)
 		return 0;
 	if (mt)
 		return mt->num_slots != num_slots ? -EINVAL : 0;

 	mt = kzalloc(struct_size(mt, slots, num_slots), GFP_KERNEL);
 	if (!mt)
 		goto err_mem;

 	mt->num_slots = num_slots;
 	mt->flags = flags;
 	input_set_abs_params(dev, ABS_MT_SLOT, 0, num_slots - 1, 0, 0);
 	input_set_abs_params(dev, ABS_MT_TRACKING_ID, 0, TRKID_MAX, 0, 0);

 	if (flags & (INPUT_MT_POINTER | INPUT_MT_DIRECT)) {
 		__set_bit(EV_KEY, dev->evbit);
 		__set_bit(BTN_TOUCH, dev->keybit);

 		copy_abs(dev, ABS_X, ABS_MT_POSITION_X);
 		copy_abs(dev, ABS_Y, ABS_MT_POSITION_Y);
 		copy_abs(dev, ABS_PRESSURE, ABS_MT_PRESSURE);
 	}
 	if (flags & INPUT_MT_POINTER) {
 		__set_bit(BTN_TOOL_FINGER, dev->keybit);
 		__set_bit(BTN_TOOL_DOUBLETAP, dev->keybit);
 		if (num_slots >= 3)
 			__set_bit(BTN_TOOL_TRIPLETAP, dev->keybit);
 		if (num_slots >= 4)
 			__set_bit(BTN_TOOL_QUADTAP, dev->keybit);
 		if (num_slots >= 5)
 			__set_bit(BTN_TOOL_QUINTTAP, dev->keybit);
 		__set_bit(INPUT_PROP_POINTER, dev->propbit);
 	}
 	if (flags & INPUT_MT_DIRECT)
 		__set_bit(INPUT_PROP_DIRECT, dev->propbit);
 	if (flags & INPUT_MT_SEMI_MT)
 		__set_bit(INPUT_PROP_SEMI_MT, dev->propbit);
 	if (flags & INPUT_MT_TRACK) {
 		unsigned int n2 = num_slots * num_slots;
 		mt->red = kcalloc(n2, sizeof(*mt->red), GFP_KERNEL);
 		if (!mt->red)
 			goto err_mem;
 	}

 	/* Mark slots as 'inactive' */
 	for (i = 0; i < num_slots; i++)
 		input_mt_set_value(&mt->slots[i], ABS_MT_TRACKING_ID, -1);

 	/* Mark slots as 'unused' */
 	mt->frame = 1;

 	dev->mt = mt;
 	return 0;
 err_mem:
 	kfree(mt);
 	return -ENOMEM;
 }
 EXPORT_SYMBOL(input_mt_init_slots);

 /**
  * input_mt_destroy_slots() - frees the MT slots of the input device
  * @dev: input device with allocated MT slots
  *
  * This function is only needed in error path as the input core will
  * automatically free the MT slots when the device is destroyed.
  */
 void input_mt_destroy_slots(struct input_dev *dev)
 {
 	if (dev->mt) {
 		kfree(dev->mt->red);
 		kfree(dev->mt);
 	}
 	dev->mt = NULL;
 }
 EXPORT_SYMBOL(input_mt_destroy_slots);

 /**
  * input_mt_report_slot_state() - report contact state
  * @dev: input device with allocated MT slots
  * @tool_type: the tool type to use in this slot
  * @active: true if contact is active, false otherwise
  *
  * Reports a contact via ABS_MT_TRACKING_ID, and optionally
  * ABS_MT_TOOL_TYPE. If active is true and the slot is currently
  * inactive, or if the tool type is changed, a new tracking id is
  * assigned to the slot. The tool type is only reported if the
  * corresponding absbit field is set.
  *
  * Returns true if contact is active.
  */
 bool input_mt_report_slot_state(struct input_dev *dev,
 				unsigned int tool_type, bool active)
 {
 	struct input_mt *mt = dev->mt;
 	struct input_mt_slot *slot;
 	int id;

 	if (!mt)
 		return false;

 	slot = &mt->slots[mt->slot];
 	slot->frame = mt->frame;

 	if (!active) {
 		input_event(dev, EV_ABS, ABS_MT_TRACKING_ID, -1);
 		return false;
 	}

 	id = input_mt_get_value(slot, ABS_MT_TRACKING_ID);
 	if (id < 0)
 		id = input_mt_new_trkid(mt);

 	input_event(dev, EV_ABS, ABS_MT_TRACKING_ID, id);
 	input_event(dev, EV_ABS, ABS_MT_TOOL_TYPE, tool_type);

 	return true;
 }
 EXPORT_SYMBOL(input_mt_report_slot_state);

 /**
  * input_mt_report_finger_count() - report contact count
  * @dev: input device with allocated MT slots
  * @count: the number of contacts
  *
  * Reports the contact count via BTN_TOOL_FINGER, BTN_TOOL_DOUBLETAP,
  * BTN_TOOL_TRIPLETAP and BTN_TOOL_QUADTAP.
  *
  * The input core ensures only the KEY events already setup for
  * this device will produce output.
  */
 void input_mt_report_finger_count(struct input_dev *dev, int count)
 {
 	input_event(dev, EV_KEY, BTN_TOOL_FINGER, count == 1);
 	input_event(dev, EV_KEY, BTN_TOOL_DOUBLETAP, count == 2);
 	input_event(dev, EV_KEY, BTN_TOOL_TRIPLETAP, count == 3);
 	input_event(dev, EV_KEY, BTN_TOOL_QUADTAP, count == 4);
 	input_event(dev, EV_KEY, BTN_TOOL_QUINTTAP, count == 5);
 }
 EXPORT_SYMBOL(input_mt_report_finger_count);

 /**
  * input_mt_report_pointer_emulation() - common pointer emulation
  * @dev: input device with allocated MT slots
  * @use_count: report number of active contacts as finger count
  *
  * Performs legacy pointer emulation via BTN_TOUCH, ABS_X, ABS_Y and
  * ABS_PRESSURE. Touchpad finger count is emulated if use_count is true.
  *
  * The input core ensures only the KEY and ABS axes already setup for
  * this device will produce output.
  */
 void input_mt_report_pointer_emulation(struct input_dev *dev, bool use_count)
 {
 	struct input_mt *mt = dev->mt;
 	struct input_mt_slot *oldest;
 	int oldid, count, i;

 	if (!mt)
 		return;

 	oldest = NULL;
 	oldid = mt->trkid;
 	count = 0;

 	for (i = 0; i < mt->num_slots; ++i) {
 		struct input_mt_slot *ps = &mt->slots[i];
 		int id = input_mt_get_value(ps, ABS_MT_TRACKING_ID);

 		if (id < 0)
 			continue;
 		if ((id - oldid) & TRKID_SGN) {
 			oldest = ps;
 			oldid = id;
 		}
 		count++;
 	}

 	input_event(dev, EV_KEY, BTN_TOUCH, count > 0);

 	if (use_count) {
 		if (count == 0 &&
 		    !test_bit(ABS_MT_DISTANCE, dev->absbit) &&
 		    test_bit(ABS_DISTANCE, dev->absbit) &&
 		    input_abs_get_val(dev, ABS_DISTANCE) != 0) {
 			/*
 			 * Force reporting BTN_TOOL_FINGER for devices that
 			 * only report general hover (and not per-contact
 			 * distance) when contact is in proximity but not
 			 * on the surface.
 			 */
 			count = 1;
 		}

 		input_mt_report_finger_count(dev, count);
 	}

 	if (oldest) {
 		int x = input_mt_get_value(oldest, ABS_MT_POSITION_X);
 		int y = input_mt_get_value(oldest, ABS_MT_POSITION_Y);

 		input_event(dev, EV_ABS, ABS_X, x);
 		input_event(dev, EV_ABS, ABS_Y, y);

 		if (test_bit(ABS_MT_PRESSURE, dev->absbit)) {
 			int p = input_mt_get_value(oldest, ABS_MT_PRESSURE);
 			input_event(dev, EV_ABS, ABS_PRESSURE, p);
 		}
 	} else {
 		if (test_bit(ABS_MT_PRESSURE, dev->absbit))
 			input_event(dev, EV_ABS, ABS_PRESSURE, 0);
 	}
 }
 EXPORT_SYMBOL(input_mt_report_pointer_emulation);

 static void __input_mt_drop_unused(struct input_dev *dev, struct input_mt *mt)
 {
 	int i;

 	for (i = 0; i < mt->num_slots; i++) {
 		if (!input_mt_is_used(mt, &mt->slots[i])) {
 			input_mt_slot(dev, i);
 			input_event(dev, EV_ABS, ABS_MT_TRACKING_ID, -1);
 		}
 	}
 }

 /**
  * input_mt_drop_unused() - Inactivate slots not seen in this frame
  * @dev: input device with allocated MT slots
  *
  * Lift all slots not seen since the last call to this function.
  */
 void input_mt_drop_unused(struct input_dev *dev)
 {
 	struct input_mt *mt = dev->mt;

 	if (mt) {
 		__input_mt_drop_unused(dev, mt);
 		mt->frame++;
 	}
 }
 EXPORT_SYMBOL(input_mt_drop_unused);

 /**
  * input_mt_sync_frame() - synchronize mt frame
  * @dev: input device with allocated MT slots
  *
  * Close the frame and prepare the internal state for a new one.
  * Depending on the flags, marks unused slots as inactive and performs
  * pointer emulation.
  */
 void input_mt_sync_frame(struct input_dev *dev)
 {
 	struct input_mt *mt = dev->mt;
 	bool use_count = false;

 	if (!mt)
 		return;

 	if (mt->flags & INPUT_MT_DROP_UNUSED)
 		__input_mt_drop_unused(dev, mt);

 	if ((mt->flags & INPUT_MT_POINTER) && !(mt->flags & INPUT_MT_SEMI_MT))
 		use_count = true;

 	input_mt_report_pointer_emulation(dev, use_count);

 	mt->frame++;
 }
 EXPORT_SYMBOL(input_mt_sync_frame);

 static int adjust_dual(int *begin, int step, int *end, int eq, int mu)
 {
 	int f, *p, s, c;

 	if (begin == end)
 		return 0;

 	f = *begin;
 	p = begin + step;
 	s = p == end ? f + 1 : *p;

 	for (; p != end; p += step)
 		if (*p < f)
 			s = f, f = *p;
 		else if (*p < s)
 			s = *p;

 	c = (f + s + 1) / 2;
 	if (c == 0 || (c > mu && (!eq || mu > 0)))
 		return 0;
 	/* Improve convergence for positive matrices by penalizing overcovers */
 	if (s < 0 && mu <= 0)
 		c *= 2;

 	for (p = begin; p != end; p += step)
 		*p -= c;

 	return (c < s && s <= 0) || (f >= 0 && f < c);
 }

 static void find_reduced_matrix(int *w, int nr, int nc, int nrc, int mu)
 {
 	int i, k, sum;

 	for (k = 0; k < nrc; k++) {
 		for (i = 0; i < nr; i++)
 			adjust_dual(w + i, nr, w + i + nrc, nr <= nc, mu);
 		sum = 0;
 		for (i = 0; i < nrc; i += nr)
 			sum += adjust_dual(w + i, 1, w + i + nr, nc <= nr, mu);
 		if (!sum)
 			break;
 	}
 }

 static int input_mt_set_matrix(struct input_mt *mt,
 			       const struct input_mt_pos *pos, int num_pos,
 			       int mu)
 {
 	const struct input_mt_pos *p;
 	struct input_mt_slot *s;
 	int *w = mt->red;
 	int x, y;

 	for (s = mt->slots; s != mt->slots + mt->num_slots; s++) {
 		if (!input_mt_is_active(s))
 			continue;
 		x = input_mt_get_value(s, ABS_MT_POSITION_X);
 		y = input_mt_get_value(s, ABS_MT_POSITION_Y);
 		for (p = pos; p != pos + num_pos; p++) {
 			int dx = x - p->x, dy = y - p->y;
 			*w++ = dx * dx + dy * dy - mu;
 		}
 	}

 	return w - mt->red;
 }

 static void input_mt_set_slots(struct input_mt *mt,
 			       int *slots, int num_pos)
 {
 	struct input_mt_slot *s;
 	int *w = mt->red, j;

 	for (j = 0; j != num_pos; j++)
 		slots[j] = -1;

 	for (s = mt->slots; s != mt->slots + mt->num_slots; s++) {
 		if (!input_mt_is_active(s))
 			continue;

 		for (j = 0; j != num_pos; j++) {
 			if (w[j] < 0) {
 				slots[j] = s - mt->slots;
 				break;
 			}
 		}

 		w += num_pos;
 	}

 	for (s = mt->slots; s != mt->slots + mt->num_slots; s++) {
 		if (input_mt_is_active(s))
 			continue;

 		for (j = 0; j != num_pos; j++) {
 			if (slots[j] < 0) {
 				slots[j] = s - mt->slots;
 				break;
 			}
 		}
 	}
 }

 /**
  * input_mt_assign_slots() - perform a best-match assignment
  * @dev: input device with allocated MT slots
  * @slots: the slot assignment to be filled
  * @pos: the position array to match
  * @num_pos: number of positions
  * @dmax: maximum ABS_MT_POSITION displacement (zero for infinite)
  *
  * Performs a best match against the current contacts and returns
  * the slot assignment list. New contacts are assigned to unused
  * slots.
  *
  * The assignments are balanced so that all coordinate displacements are
  * below the euclidian distance dmax. If no such assignment can be found,
  * some contacts are assigned to unused slots.
  *
  * Returns zero on success, or negative error in case of failure.
  */
 int input_mt_assign_slots(struct input_dev *dev, int *slots,
 			  const struct input_mt_pos *pos, int num_pos,
 			  int dmax)
 {
 	struct input_mt *mt = dev->mt;
 	int mu = 2 * dmax * dmax;
 	int nrc;

 	if (!mt || !mt->red)
 		return -ENXIO;
 	if (num_pos > mt->num_slots)
 		return -EINVAL;
 	if (num_pos < 1)
 		return 0;

 	nrc = input_mt_set_matrix(mt, pos, num_pos, mu);
 	find_reduced_matrix(mt->red, num_pos, nrc / num_pos, nrc, mu);
 	input_mt_set_slots(mt, slots, num_pos);

 	return 0;
 }
 EXPORT_SYMBOL(input_mt_assign_slots);

 /**
  * input_mt_get_slot_by_key() - return slot matching key
  * @dev: input device with allocated MT slots
  * @key: the key of the sought slot
  *
  * Returns the slot of the given key, if it exists, otherwise
  * set the key on the first unused slot and return.
  *
  * If no available slot can be found, -1 is returned.
  * Note that for this function to work properly, input_mt_sync_frame() has
  * to be called at each frame.
  */
 int input_mt_get_slot_by_key(struct input_dev *dev, int key)
 {
 	struct input_mt *mt = dev->mt;
 	struct input_mt_slot *s;

 	if (!mt)
 		return -1;

 	for (s = mt->slots; s != mt->slots + mt->num_slots; s++)
 		if (input_mt_is_active(s) && s->key == key)
 			return s - mt->slots;

 	for (s = mt->slots; s != mt->slots + mt->num_slots; s++)
 		if (!input_mt_is_active(s) && !input_mt_is_used(mt, s)) {
 			s->key = key;
 			return s - mt->slots;
 		}

 	return -1;
 }
 EXPORT_SYMBOL(input_mt_get_slot_by_key);
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Input Multitouch Library
	*
	* Copyright (c) 2008-2010 Henrik Rydberg
	*/

	#include <linux/input/mt.h>
	#include <linux/export.h>
	#include <linux/slab.h>

	#define TRKID_SGN ((TRKID_MAX + 1) >> 1)

	static void copy_abs(struct input_dev *dev, unsigned int dst, unsigned int src)
	{
	if (dev->absinfo && test_bit(src, dev->absbit)) {
	dev->absinfo[dst] = dev->absinfo[src];
	dev->absinfo[dst].fuzz = 0;
	__set_bit(dst, dev->absbit);
	}
	}

	/**
	* 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
	* @flags: mt tasks to handle in core
	*
	* 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.
	* Depending on the flags set, it also performs pointer emulation and
	* frame synchronization.
	*
	* 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,
	unsigned int flags)
	{
	struct input_mt *mt = dev->mt;
	int i;

	if (!num_slots)
	return 0;
	if (mt)
	return mt->num_slots != num_slots ? -EINVAL : 0;

	mt = kzalloc(struct_size(mt, slots, num_slots), GFP_KERNEL);
	if (!mt)
	goto err_mem;

	mt->num_slots = num_slots;
	mt->flags = flags;
	input_set_abs_params(dev, ABS_MT_SLOT, 0, num_slots - 1, 0, 0);
	input_set_abs_params(dev, ABS_MT_TRACKING_ID, 0, TRKID_MAX, 0, 0);

	if (flags & (INPUT_MT_POINTER \| INPUT_MT_DIRECT)) {
	__set_bit(EV_KEY, dev->evbit);
	__set_bit(BTN_TOUCH, dev->keybit);

	copy_abs(dev, ABS_X, ABS_MT_POSITION_X);
	copy_abs(dev, ABS_Y, ABS_MT_POSITION_Y);
	copy_abs(dev, ABS_PRESSURE, ABS_MT_PRESSURE);
	}
	if (flags & INPUT_MT_POINTER) {
	__set_bit(BTN_TOOL_FINGER, dev->keybit);
	__set_bit(BTN_TOOL_DOUBLETAP, dev->keybit);
	if (num_slots >= 3)
	__set_bit(BTN_TOOL_TRIPLETAP, dev->keybit);
	if (num_slots >= 4)
	__set_bit(BTN_TOOL_QUADTAP, dev->keybit);
	if (num_slots >= 5)
	__set_bit(BTN_TOOL_QUINTTAP, dev->keybit);
	__set_bit(INPUT_PROP_POINTER, dev->propbit);
	}
	if (flags & INPUT_MT_DIRECT)
	__set_bit(INPUT_PROP_DIRECT, dev->propbit);
	if (flags & INPUT_MT_SEMI_MT)
	__set_bit(INPUT_PROP_SEMI_MT, dev->propbit);
	if (flags & INPUT_MT_TRACK) {
	unsigned int n2 = num_slots * num_slots;
	mt->red = kcalloc(n2, sizeof(*mt->red), GFP_KERNEL);
	if (!mt->red)
	goto err_mem;
	}

	/* Mark slots as 'inactive' */
	for (i = 0; i < num_slots; i++)
	input_mt_set_value(&mt->slots[i], ABS_MT_TRACKING_ID, -1);

	/* Mark slots as 'unused' */
	mt->frame = 1;

	dev->mt = mt;
	return 0;
	err_mem:
	kfree(mt);
	return -ENOMEM;
	}
	EXPORT_SYMBOL(input_mt_init_slots);

	/**
	* input_mt_destroy_slots() - frees the MT slots of the input device
	* @dev: input device with allocated MT slots
	*
	* This function is only needed in error path as the input core will
	* automatically free the MT slots when the device is destroyed.
	*/
	void input_mt_destroy_slots(struct input_dev *dev)
	{
	if (dev->mt) {
	kfree(dev->mt->red);
	kfree(dev->mt);
	}
	dev->mt = NULL;
	}
	EXPORT_SYMBOL(input_mt_destroy_slots);

	/**
	* input_mt_report_slot_state() - report contact state
	* @dev: input device with allocated MT slots
	* @tool_type: the tool type to use in this slot
	* @active: true if contact is active, false otherwise
	*
	* Reports a contact via ABS_MT_TRACKING_ID, and optionally
	* ABS_MT_TOOL_TYPE. If active is true and the slot is currently
	* inactive, or if the tool type is changed, a new tracking id is
	* assigned to the slot. The tool type is only reported if the
	* corresponding absbit field is set.
	*
	* Returns true if contact is active.
	*/
	bool input_mt_report_slot_state(struct input_dev *dev,
	unsigned int tool_type, bool active)
	{
	struct input_mt *mt = dev->mt;
	struct input_mt_slot *slot;
	int id;

	if (!mt)
	return false;

	slot = &mt->slots[mt->slot];
	slot->frame = mt->frame;

	if (!active) {
	input_event(dev, EV_ABS, ABS_MT_TRACKING_ID, -1);
	return false;
	}

	id = input_mt_get_value(slot, ABS_MT_TRACKING_ID);
	if (id < 0)
	id = input_mt_new_trkid(mt);

	input_event(dev, EV_ABS, ABS_MT_TRACKING_ID, id);
	input_event(dev, EV_ABS, ABS_MT_TOOL_TYPE, tool_type);

	return true;
	}
	EXPORT_SYMBOL(input_mt_report_slot_state);

	/**
	* input_mt_report_finger_count() - report contact count
	* @dev: input device with allocated MT slots
	* @count: the number of contacts
	*
	* Reports the contact count via BTN_TOOL_FINGER, BTN_TOOL_DOUBLETAP,
	* BTN_TOOL_TRIPLETAP and BTN_TOOL_QUADTAP.
	*
	* The input core ensures only the KEY events already setup for
	* this device will produce output.
	*/
	void input_mt_report_finger_count(struct input_dev *dev, int count)
	{
	input_event(dev, EV_KEY, BTN_TOOL_FINGER, count == 1);
	input_event(dev, EV_KEY, BTN_TOOL_DOUBLETAP, count == 2);
	input_event(dev, EV_KEY, BTN_TOOL_TRIPLETAP, count == 3);
	input_event(dev, EV_KEY, BTN_TOOL_QUADTAP, count == 4);
	input_event(dev, EV_KEY, BTN_TOOL_QUINTTAP, count == 5);
	}
	EXPORT_SYMBOL(input_mt_report_finger_count);

	/**
	* input_mt_report_pointer_emulation() - common pointer emulation
	* @dev: input device with allocated MT slots
	* @use_count: report number of active contacts as finger count
	*
	* Performs legacy pointer emulation via BTN_TOUCH, ABS_X, ABS_Y and
	* ABS_PRESSURE. Touchpad finger count is emulated if use_count is true.
	*
	* The input core ensures only the KEY and ABS axes already setup for
	* this device will produce output.
	*/
	void input_mt_report_pointer_emulation(struct input_dev *dev, bool use_count)
	{
	struct input_mt *mt = dev->mt;
	struct input_mt_slot *oldest;
	int oldid, count, i;

	if (!mt)
	return;

	oldest = NULL;
	oldid = mt->trkid;
	count = 0;

	for (i = 0; i < mt->num_slots; ++i) {
	struct input_mt_slot *ps = &mt->slots[i];
	int id = input_mt_get_value(ps, ABS_MT_TRACKING_ID);

	if (id < 0)
	continue;
	if ((id - oldid) & TRKID_SGN) {
	oldest = ps;
	oldid = id;
	}
	count++;
	}

	input_event(dev, EV_KEY, BTN_TOUCH, count > 0);

	if (use_count) {
	if (count == 0 &&
	!test_bit(ABS_MT_DISTANCE, dev->absbit) &&
	test_bit(ABS_DISTANCE, dev->absbit) &&
	input_abs_get_val(dev, ABS_DISTANCE) != 0) {
	/*
	* Force reporting BTN_TOOL_FINGER for devices that
	* only report general hover (and not per-contact
	* distance) when contact is in proximity but not
	* on the surface.
	*/
	count = 1;
	}

	input_mt_report_finger_count(dev, count);
	}

	if (oldest) {
	int x = input_mt_get_value(oldest, ABS_MT_POSITION_X);
	int y = input_mt_get_value(oldest, ABS_MT_POSITION_Y);

	input_event(dev, EV_ABS, ABS_X, x);
	input_event(dev, EV_ABS, ABS_Y, y);

	if (test_bit(ABS_MT_PRESSURE, dev->absbit)) {
	int p = input_mt_get_value(oldest, ABS_MT_PRESSURE);
	input_event(dev, EV_ABS, ABS_PRESSURE, p);
	}
	} else {
	if (test_bit(ABS_MT_PRESSURE, dev->absbit))
	input_event(dev, EV_ABS, ABS_PRESSURE, 0);
	}
	}
	EXPORT_SYMBOL(input_mt_report_pointer_emulation);

	static void __input_mt_drop_unused(struct input_dev dev, struct input_mt mt)
	{
	int i;

	for (i = 0; i < mt->num_slots; i++) {
	if (!input_mt_is_used(mt, &mt->slots[i])) {
	input_mt_slot(dev, i);
	input_event(dev, EV_ABS, ABS_MT_TRACKING_ID, -1);
	}
	}
	}

	/**
	* input_mt_drop_unused() - Inactivate slots not seen in this frame
	* @dev: input device with allocated MT slots
	*
	* Lift all slots not seen since the last call to this function.
	*/
	void input_mt_drop_unused(struct input_dev *dev)
	{
	struct input_mt *mt = dev->mt;

	if (mt) {
	__input_mt_drop_unused(dev, mt);
	mt->frame++;
	}
	}
	EXPORT_SYMBOL(input_mt_drop_unused);

	/**
	* input_mt_sync_frame() - synchronize mt frame
	* @dev: input device with allocated MT slots
	*
	* Close the frame and prepare the internal state for a new one.
	* Depending on the flags, marks unused slots as inactive and performs
	* pointer emulation.
	*/
	void input_mt_sync_frame(struct input_dev *dev)
	{
	struct input_mt *mt = dev->mt;
	bool use_count = false;

	if (!mt)
	return;

	if (mt->flags & INPUT_MT_DROP_UNUSED)
	__input_mt_drop_unused(dev, mt);

	if ((mt->flags & INPUT_MT_POINTER) && !(mt->flags & INPUT_MT_SEMI_MT))
	use_count = true;

	input_mt_report_pointer_emulation(dev, use_count);

	mt->frame++;
	}
	EXPORT_SYMBOL(input_mt_sync_frame);

	static int adjust_dual(int begin, int step, int end, int eq, int mu)
	{
	int f, *p, s, c;

	if (begin == end)
	return 0;

	f = *begin;
	p = begin + step;
	s = p == end ? f + 1 : *p;

	for (; p != end; p += step)
	if (*p < f)
	s = f, f = *p;
	else if (*p < s)
	s = *p;

	c = (f + s + 1) / 2;
	if (c == 0 \|\| (c > mu && (!eq \|\| mu > 0)))
	return 0;
	/* Improve convergence for positive matrices by penalizing overcovers */
	if (s < 0 && mu <= 0)
	c *= 2;

	for (p = begin; p != end; p += step)
	*p -= c;

	return (c < s && s <= 0) \|\| (f >= 0 && f < c);
	}

	static void find_reduced_matrix(int *w, int nr, int nc, int nrc, int mu)
	{
	int i, k, sum;

	for (k = 0; k < nrc; k++) {
	for (i = 0; i < nr; i++)
	adjust_dual(w + i, nr, w + i + nrc, nr <= nc, mu);
	sum = 0;
	for (i = 0; i < nrc; i += nr)
	sum += adjust_dual(w + i, 1, w + i + nr, nc <= nr, mu);
	if (!sum)
	break;
	}
	}

	static int input_mt_set_matrix(struct input_mt *mt,
	const struct input_mt_pos *pos, int num_pos,
	int mu)
	{
	const struct input_mt_pos *p;
	struct input_mt_slot *s;
	int *w = mt->red;
	int x, y;

	for (s = mt->slots; s != mt->slots + mt->num_slots; s++) {
	if (!input_mt_is_active(s))
	continue;
	x = input_mt_get_value(s, ABS_MT_POSITION_X);
	y = input_mt_get_value(s, ABS_MT_POSITION_Y);
	for (p = pos; p != pos + num_pos; p++) {
	int dx = x - p->x, dy = y - p->y;
	w++ = dx dx + dy * dy - mu;
	}
	}

	return w - mt->red;
	}

	static void input_mt_set_slots(struct input_mt *mt,
	int *slots, int num_pos)
	{
	struct input_mt_slot *s;
	int *w = mt->red, j;

	for (j = 0; j != num_pos; j++)
	slots[j] = -1;

	for (s = mt->slots; s != mt->slots + mt->num_slots; s++) {
	if (!input_mt_is_active(s))
	continue;

	for (j = 0; j != num_pos; j++) {
	if (w[j] < 0) {
	slots[j] = s - mt->slots;
	break;
	}
	}

	w += num_pos;
	}

	for (s = mt->slots; s != mt->slots + mt->num_slots; s++) {
	if (input_mt_is_active(s))
	continue;

	for (j = 0; j != num_pos; j++) {
	if (slots[j] < 0) {
	slots[j] = s - mt->slots;
	break;
	}
	}
	}
	}

	/**
	* input_mt_assign_slots() - perform a best-match assignment
	* @dev: input device with allocated MT slots
	* @slots: the slot assignment to be filled
	* @pos: the position array to match
	* @num_pos: number of positions
	* @dmax: maximum ABS_MT_POSITION displacement (zero for infinite)
	*
	* Performs a best match against the current contacts and returns
	* the slot assignment list. New contacts are assigned to unused
	* slots.
	*
	* The assignments are balanced so that all coordinate displacements are
	* below the euclidian distance dmax. If no such assignment can be found,
	* some contacts are assigned to unused slots.
	*
	* Returns zero on success, or negative error in case of failure.
	*/
	int input_mt_assign_slots(struct input_dev dev, int slots,
	const struct input_mt_pos *pos, int num_pos,
	int dmax)
	{
	struct input_mt *mt = dev->mt;
	int mu = 2 * dmax * dmax;
	int nrc;

	if (!mt \|\| !mt->red)
	return -ENXIO;
	if (num_pos > mt->num_slots)
	return -EINVAL;
	if (num_pos < 1)
	return 0;

	nrc = input_mt_set_matrix(mt, pos, num_pos, mu);
	find_reduced_matrix(mt->red, num_pos, nrc / num_pos, nrc, mu);
	input_mt_set_slots(mt, slots, num_pos);

	return 0;
	}
	EXPORT_SYMBOL(input_mt_assign_slots);

	/**
	* input_mt_get_slot_by_key() - return slot matching key
	* @dev: input device with allocated MT slots
	* @key: the key of the sought slot
	*
	* Returns the slot of the given key, if it exists, otherwise
	* set the key on the first unused slot and return.
	*
	* If no available slot can be found, -1 is returned.
	* Note that for this function to work properly, input_mt_sync_frame() has
	* to be called at each frame.
	*/
	int input_mt_get_slot_by_key(struct input_dev *dev, int key)
	{
	struct input_mt *mt = dev->mt;
	struct input_mt_slot *s;

	if (!mt)
	return -1;

	for (s = mt->slots; s != mt->slots + mt->num_slots; s++)
	if (input_mt_is_active(s) && s->key == key)
	return s - mt->slots;

	for (s = mt->slots; s != mt->slots + mt->num_slots; s++)
	if (!input_mt_is_active(s) && !input_mt_is_used(mt, s)) {
	s->key = key;
	return s - mt->slots;
	}

	return -1;
	}
	EXPORT_SYMBOL(input_mt_get_slot_by_key);