From 448c7f3830ca283e485aa943279acea6bde8b270 Mon Sep 17 00:00:00 2001 From: Henrik Rydberg Date: Sun, 1 Feb 2015 11:25:14 -0800 Subject: Input: MT - add support for balanced slot assignment Some devices are not fast enough to differentiate between a fast-moving contact and a new contact. This problem cannot be fully resolved because information is truly missing, but it is possible to safe-guard against obvious mistakes by restricting movement with a maximum displacement. The new problem formulation for dmax > 0 cannot benefit from the speedup for positive definite matrices, but since the convergence is faster, the result is about the same. For a handful of contacts, the latency difference is truly negligible. Suggested-by: Benjamin Tissoires Tested-by: Benjamin Tissoires Signed-off-by: Henrik Rydberg Signed-off-by: Dmitry Torokhov --- drivers/input/input-mt.c | 31 ++++++++++++++++++++----------- 1 file changed, 20 insertions(+), 11 deletions(-) (limited to 'drivers/input/input-mt.c') diff --git a/drivers/input/input-mt.c b/drivers/input/input-mt.c index fbe29fcb15c5..cb150a1dbaff 100644 --- a/drivers/input/input-mt.c +++ b/drivers/input/input-mt.c @@ -293,7 +293,7 @@ void input_mt_sync_frame(struct input_dev *dev) } EXPORT_SYMBOL(input_mt_sync_frame); -static int adjust_dual(int *begin, int step, int *end, int eq) +static int adjust_dual(int *begin, int step, int *end, int eq, int mu) { int f, *p, s, c; @@ -311,9 +311,10 @@ static int adjust_dual(int *begin, int step, int *end, int eq) s = *p; c = (f + s + 1) / 2; - if (c == 0 || (c > 0 && !eq)) + if (c == 0 || (c > mu && (!eq || mu > 0))) return 0; - if (s < 0) + /* Improve convergence for positive matrices by penalizing overcovers */ + if (s < 0 && mu <= 0) c *= 2; for (p = begin; p != end; p += step) @@ -322,23 +323,24 @@ static int adjust_dual(int *begin, int step, int *end, int eq) return (c < s && s <= 0) || (f >= 0 && f < c); } -static void find_reduced_matrix(int *w, int nr, int nc, int nrc) +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); + 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); + 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) + const struct input_mt_pos *pos, int num_pos, + int mu) { const struct input_mt_pos *p; struct input_mt_slot *s; @@ -352,7 +354,7 @@ static int input_mt_set_matrix(struct input_mt *mt, 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; + *w++ = dx * dx + dy * dy - mu; } } @@ -393,17 +395,24 @@ static void input_mt_set_slots(struct input_mt *mt, * @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) + 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) @@ -413,8 +422,8 @@ int input_mt_assign_slots(struct input_dev *dev, int *slots, 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); + 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; -- cgit