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Commit 7c1a8789 authored by Henrik Rydberg's avatar Henrik Rydberg
Browse files

Input: MT - Add in-kernel tracking 



With the INPUT_MT_TRACK flag set, the function input_mt_assign_slots()
can be used to match a new set of contacts against the currently used
slots. The algorithm used is based on Lagrange relaxation, and performs
very well in practice; slower than mtdev for a few corner cases, but
faster in most commonly occuring cases.

Tested-by: default avatarBenjamin Tissoires <benjamin.tissoires@enac.fr>
Acked-by: default avatarDmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: default avatarHenrik Rydberg <rydberg@euromail.se>
parent 55e49089

drivers/input/input-mt.c

+142 −2
Original line number Diff line number Diff line
@@ -46,7 +46,7 @@ int input_mt_init_slots(struct input_dev *dev, unsigned int num_slots, 


	mt = kzalloc(sizeof(*mt) + num_slots * sizeof(*mt->slots), GFP_KERNEL);

	if (!mt)

		return -ENOMEM;

		goto err_mem;



	mt->num_slots = num_slots;

	mt->flags = flags;
@@ -74,6 +74,12 @@ int input_mt_init_slots(struct input_dev *dev, unsigned int num_slots, 
	}

	if (flags & INPUT_MT_DIRECT)

		__set_bit(INPUT_PROP_DIRECT, 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 'unused' */

	for (i = 0; i < num_slots; i++)
@@ -81,6 +87,9 @@ int input_mt_init_slots(struct input_dev *dev, unsigned int num_slots, 


	dev->mt = mt;

	return 0;

err_mem:

	kfree(mt);

	return -ENOMEM;

}

EXPORT_SYMBOL(input_mt_init_slots);
@@ -93,7 +102,10 @@ EXPORT_SYMBOL(input_mt_init_slots); 
 */

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);
@@ -243,3 +255,131 @@ void input_mt_sync_frame(struct input_dev *dev) 
	mt->frame++;

}

EXPORT_SYMBOL(input_mt_sync_frame);



static int adjust_dual(int *begin, int step, int *end, int eq)

{

	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 > 0 && !eq))

		return 0;

	if (s < 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 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);

		sum = 0;

		for (i = 0; i < nrc; i += nr)

			sum += adjust_dual(w + i, 1, w + i + nr, nc <= nr);

		if (!sum)

			break;

	}

}



static int input_mt_set_matrix(struct input_mt *mt,

			       const struct input_mt_pos *pos, int num_pos)

{

	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;

		}

	}



	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, *p;



	for (p = slots; p != slots + num_pos; p++)

		*p = -1;



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

		if (!input_mt_is_active(s))

			continue;

		for (p = slots; p != slots + num_pos; p++)

			if (*w++ < 0)

				*p = s - mt->slots;

	}



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

		if (input_mt_is_active(s))

			continue;

		for (p = slots; p != slots + num_pos; p++)

			if (*p < 0) {

				*p = 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

 *

 * Performs a best match against the current contacts and returns

 * the slot assignment list. New 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)

{

	struct input_mt *mt = dev->mt;

	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);

	find_reduced_matrix(mt->red, num_pos, nrc / num_pos, nrc);

	input_mt_set_slots(mt, slots, num_pos);



	return 0;

}

EXPORT_SYMBOL(input_mt_assign_slots);

include/linux/input/mt.h

+21 −0
Original line number Diff line number Diff line
@@ -18,6 +18,8 @@ 
#define INPUT_MT_POINTER	0x0001	/* pointer device, e.g. trackpad */

#define INPUT_MT_DIRECT		0x0002	/* direct device, e.g. touchscreen */

#define INPUT_MT_DROP_UNUSED	0x0004	/* drop contacts not seen in frame */

#define INPUT_MT_TRACK		0x0008	/* use in-kernel tracking */



/**

 * struct input_mt_slot - represents the state of an input MT slot

 * @abs: holds current values of ABS_MT axes for this slot
@@ -35,6 +37,7 @@ struct input_mt_slot { 
 * @slot: MT slot currently being transmitted

 * @flags: input_mt operation flags

 * @frame: increases every time input_mt_sync_frame() is called

 * @red: reduced cost matrix for in-kernel tracking

 * @slots: array of slots holding current values of tracked contacts

 */

struct input_mt {
@@ -43,6 +46,7 @@ struct input_mt { 
	int slot;

	unsigned int flags;

	unsigned int frame;

	int *red;

	struct input_mt_slot slots[];

};
@@ -58,6 +62,11 @@ static inline int input_mt_get_value(const struct input_mt_slot *slot, 
	return slot->abs[code - ABS_MT_FIRST];

}



static inline bool input_mt_is_active(const struct input_mt_slot *slot)

{

	return input_mt_get_value(slot, ABS_MT_TRACKING_ID) >= 0;

}



int input_mt_init_slots(struct input_dev *dev, unsigned int num_slots,

			unsigned int flags);

void input_mt_destroy_slots(struct input_dev *dev);
@@ -90,4 +99,16 @@ void input_mt_report_pointer_emulation(struct input_dev *dev, bool use_count); 


void input_mt_sync_frame(struct input_dev *dev);



/**

 * struct input_mt_pos - contact position

 * @x: horizontal coordinate

 * @y: vertical coordinate

 */

struct input_mt_pos {

	s16 x, y;

};



int input_mt_assign_slots(struct input_dev *dev, int *slots,

			  const struct input_mt_pos *pos, int num_pos);



#endif