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Subject[PATCH v3 09/20] Input: MT - Add in-kernel tracking
Date
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.

Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
---
drivers/input/input-mt.c | 144 ++++++++++++++++++++++++++++++++++++++++++++++-
include/linux/input/mt.h | 21 +++++++
2 files changed, 163 insertions(+), 2 deletions(-)

diff --git a/drivers/input/input-mt.c b/drivers/input/input-mt.c
index 769c76d..2acf693 100644
--- a/drivers/input/input-mt.c
+++ b/drivers/input/input-mt.c
@@ -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)
{
- kfree(dev->mt);
+ if (dev->mt) {
+ kfree(dev->mt->red);
+ kfree(dev->mt);
+ }
dev->mt = NULL;
dev->slot = 0;
}
@@ -244,3 +256,131 @@ 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);
diff --git a/include/linux/input/mt.h b/include/linux/input/mt.h
index a11d485..10bb77c 100644
--- a/include/linux/input/mt.h
+++ b/include/linux/input/mt.h
@@ -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
@@ -34,6 +36,7 @@ struct input_mt_slot {
* @num_slots: number of MT slots the device uses
* @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 {
@@ -41,6 +44,7 @@ struct input_mt {
int num_slots;
unsigned int flags;
unsigned int frame;
+ int *red;
struct input_mt_slot slots[];
};

@@ -56,6 +60,11 @@ 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);
@@ -88,4 +97,16 @@ 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
--
1.7.12


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