text: // 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;
  		dev->absbit[BIT_WORD(dst)] |= BIT_MASK(dst);
  	}
  }
  
  /**
   * 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);
  