[PATCH 2/5] Add group filter

[Nelson]

From: Nelson Castillo <arhuaco@xxxxxxxxxxxxxxxxx>

This filter is useful to reject samples that are not reliable.
We consider that a sample is not reliable if it deviates from the Majority.

Signed-off-by: Nelson Castillo <arhuaco@xxxxxxxxxxxxxxxxx>
---

 drivers/input/touchscreen/Kconfig           |   12 +
 drivers/input/touchscreen/Makefile          |    1 
 drivers/input/touchscreen/ts_filter_group.c |  221 +++++++++++++++++++++++++++
 include/linux/ts_filter_group.h             |   39 +++++
 4 files changed, 273 insertions(+), 0 deletions(-)
 create mode 100644 drivers/input/touchscreen/ts_filter_group.c
 create mode 100644 include/linux/ts_filter_group.h

diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
index aed3eb0..09f55dd 100644
--- a/drivers/input/touchscreen/Kconfig
+++ b/drivers/input/touchscreen/Kconfig
@@ -19,6 +19,18 @@ menuconfig TOUCHSCREEN_FILTER
 	  can be combined in any order in your machine init and the parameters
 	  for them can also be set there.
 
+if TOUCHSCREEN_FILTER
+
+config TOUCHSCREEN_FILTER_GROUP
+	bool "Group Touchscreen Filter"
+	depends on INPUT_TOUCHSCREEN && TOUCHSCREEN_FILTER
+	default Y
+	help
+	  Say Y here if you want to use the Group touchscreen filter, it
+	  avoids using atypical samples.
+
+endif
+
 config TOUCHSCREEN_ADS7846
 	tristate "ADS7846/TSC2046 and ADS7843 based touchscreens"
 	depends on SPI_MASTER
diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
index 74ab26f..9ccb21a 100644
--- a/drivers/input/touchscreen/Makefile
+++ b/drivers/input/touchscreen/Makefile
@@ -32,3 +32,4 @@ wm97xx-ts-$(CONFIG_TOUCHSCREEN_WM9712)	+= wm9712.o
 wm97xx-ts-$(CONFIG_TOUCHSCREEN_WM9713)	+= wm9713.o
 obj-$(CONFIG_TOUCHSCREEN_WM97XX_MAINSTONE)	+= mainstone-wm97xx.o
 obj-$(CONFIG_TOUCHSCREEN_FILTER)	+= ts_filter.o
+obj-$(CONFIG_TOUCHSCREEN_FILTER_GROUP)	+= ts_filter_group.o
diff --git a/drivers/input/touchscreen/ts_filter_group.c b/drivers/input/touchscreen/ts_filter_group.c
new file mode 100644
index 0000000..73e3625
--- /dev/null
+++ b/drivers/input/touchscreen/ts_filter_group.c
@@ -0,0 +1,221 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ * Copyright (C) 2008 by Openmoko, Inc.
+ * Author: Nelson Castillo <arhuaco@xxxxxxxxxxxxxxxxx>
+ * All rights reserved.
+ *
+ * This filter is useful to reject samples that are not reliable. We consider
+ * that a sample is not reliable if it deviates form the Majority.
+ *
+ * 1) We collect S samples.
+ *
+ * 2) For each dimension:
+ *
+ *  - We sort the points.
+ *  - Points that are "close enough" are considered to be in the same set.
+ *  - We choose the set with more elements. If more than "threshold"
+ *    points are in this set we use the first and the last point of the set
+ *    to define the valid range for this dimension [min, max], otherwise we
+ *    discard all the points and go to step 1.
+ *
+ * 3) We consider the unsorted S samples and try to feed them to the next
+ *    filter in the chain. If one of the points of each sample
+ *    is not in the allowed range for its dimension, we discard the sample.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/sort.h>
+#include <linux/ts_filter_group.h>
+
+static void ts_filter_group_clear_internal(struct ts_filter_group *tsfg,
+					   int attempts)
+{
+	tsfg->N = 0;
+	tsfg->tries_left = attempts;
+}
+
+static void ts_filter_group_clear(struct ts_filter *tsf)
+{
+	struct ts_filter_group *tsfg = (struct ts_filter_group *)tsf;
+
+	ts_filter_group_clear_internal(tsfg, tsfg->config->attempts);
+
+	if (tsf->next) /* chain */
+		(tsf->next->api->clear)(tsf->next);
+}
+
+static struct ts_filter *ts_filter_group_create(struct platform_device *pdev,
+						void *conf, int count_coords)
+{
+	struct ts_filter_group *tsfg;
+	int i;
+
+	BUG_ON((count_coords < 1) || (count_coords > MAX_TS_FILTER_COORDS));
+
+	tsfg = kzalloc(sizeof(struct ts_filter_group), GFP_KERNEL);
+	if (!tsfg)
+		return NULL;
+
+	tsfg->config = (struct ts_filter_group_configuration *)conf;
+	tsfg->tsf.count_coords = count_coords;
+
+	BUG_ON(tsfg->config->attempts <= 0);
+
+	tsfg->samples[0] = kmalloc((2 + count_coords) * sizeof(int) *
+				   tsfg->config->extent, GFP_KERNEL);
+	if (!tsfg->samples[0]) {
+		kfree(tsfg);
+		return NULL;
+	}
+	for (i = 1; i < count_coords; ++i)
+		tsfg->samples[i] = tsfg->samples[0] + i * tsfg->config->extent;
+	tsfg->sorted_samples = tsfg->samples[0] + count_coords *
+			       tsfg->config->extent;
+	tsfg->group_size = tsfg->samples[0] + (1 + count_coords) *
+			       tsfg->config->extent;
+
+	ts_filter_group_clear_internal(tsfg, tsfg->config->attempts);
+
+	printk(KERN_INFO"  Created group ts filter len %d depth %d close %d "
+			"thresh %d\n", tsfg->config->extent, count_coords,
+			tsfg->config->close_enough, tsfg->config->threshold);
+
+	return &tsfg->tsf;
+}
+
+static void ts_filter_group_destroy(struct platform_device *pdev,
+				    struct ts_filter *tsf)
+{
+	struct ts_filter_group *tsfg = (struct ts_filter_group *)tsf;
+
+	kfree(tsfg->samples[0]); /* first guy has pointer from kmalloc */
+	kfree(tsf);
+}
+
+static void ts_filter_group_scale(struct ts_filter *tsf, int *coords)
+{
+	if (tsf->next)
+		(tsf->next->api->scale)(tsf->next, coords);
+}
+
+static int int_cmp(const void *_a, const void *_b)
+{
+	const int *a = _a;
+	const int *b = _b;
+
+	if (*a > *b)
+		return 1;
+	if (*a < *b)
+		return -1;
+	return 0;
+}
+
+static int ts_filter_group_process(struct ts_filter *tsf, int *coords)
+{
+	struct ts_filter_group *tsfg = (struct ts_filter_group *)tsf;
+	int n;
+	int i;
+	int ret = 0; /* ask for more samples by default */
+
+	BUG_ON(tsfg->N >= tsfg->config->extent);
+
+	for (n = 0; n < tsf->count_coords; n++)
+		tsfg->samples[n][tsfg->N] = coords[n];
+
+	if (++tsfg->N < tsfg->config->extent)
+		return 0;	/* we meed more samples */
+
+	for (n = 0; n < tsfg->tsf.count_coords; n++) {
+		int *v = tsfg->sorted_samples;
+		int ngroups = 0;
+		int best_size;
+		int best_idx = 0;
+		int idx = 0;
+
+		memcpy(v, tsfg->samples[n], tsfg->N * sizeof(int));
+		sort(v, tsfg->N, sizeof(int), int_cmp, NULL);
+
+		tsfg->group_size[0] = 1;
+		for (i = 1; i < tsfg->N; ++i) {
+			if (v[i] - v[i - 1] <= tsfg->config->close_enough)
+				tsfg->group_size[ngroups]++;
+			else
+				tsfg->group_size[++ngroups] = 1;
+		}
+		ngroups++;
+
+		best_size = tsfg->group_size[0];
+		for (i = 1; i < ngroups; i++) {
+			idx += tsfg->group_size[i - 1];
+			if (best_size < tsfg->group_size[i]) {
+				best_size = tsfg->group_size[i];
+				best_idx = idx;
+			}
+		}
+
+		if (best_size < tsfg->config->threshold) {
+			/* this set is not good enough for us */
+			if (--tsfg->tries_left) {
+				ts_filter_group_clear_internal
+					(tsfg, tsfg->tries_left);
+				return 0; /* ask for more samples */
+			}
+			return -1; /* we give up */
+		}
+
+		tsfg->range_min[n] = v[best_idx];
+		tsfg->range_max[n] = v[best_idx + best_size - 1];
+	}
+
+	for (i = 0; i < tsfg->N; ++i) {
+		int r;
+
+		for (n = 0; n < tsfg->tsf.count_coords; ++n) {
+			coords[n] = tsfg->samples[n][i];
+			if (coords[n] < tsfg->range_min[n] ||
+			    coords[n] > tsfg->range_max[n])
+				break;
+		}
+
+		if (n != tsfg->tsf.count_coords) /* sample not OK */
+			continue;
+
+		if (tsf->next) {
+			r = (tsf->next->api->process)(tsf->next, coords);
+			if (r)  {
+				ret = r;
+				break;
+			}
+		} else if (i == tsfg->N - 1) {
+			ret = 1;
+		}
+	}
+
+	ts_filter_group_clear_internal(tsfg, tsfg->config->attempts);
+
+	return ret;
+}
+
+struct ts_filter_api ts_filter_group_api = {
+	.create = ts_filter_group_create,
+	.destroy = ts_filter_group_destroy,
+	.clear = ts_filter_group_clear,
+	.process = ts_filter_group_process,
+	.scale = ts_filter_group_scale,
+};
+
diff --git a/include/linux/ts_filter_group.h b/include/linux/ts_filter_group.h
new file mode 100644
index 0000000..1e74c8d
--- /dev/null
+++ b/include/linux/ts_filter_group.h
@@ -0,0 +1,39 @@
+#ifndef __TS_FILTER_GROUP_H__
+#define __TS_FILTER_GROUP_H__
+
+#include <linux/ts_filter.h>
+
+/*
+ * Touchscreen group filter.
+ *
+ * Copyright (C) 2008 by Openmoko, Inc.
+ * Author: Nelson Castillo <arhuaco@xxxxxxxxxxxxxxxxx>
+ *
+ */
+
+struct ts_filter_group_configuration {
+	int extent;
+	int close_enough;
+	int threshold;
+	int attempts;
+};
+
+struct ts_filter_group {
+	struct ts_filter tsf;
+	struct ts_filter_group_configuration *config;
+
+	int N;		/* How many samples we have */
+	int *samples[MAX_TS_FILTER_COORDS];	/* the samples, our input */
+
+	int *group_size;	/* used for temporal computations */
+	int *sorted_samples;	/* used for temporal computations */
+
+	int range_max[MAX_TS_FILTER_COORDS];	/* max computed ranges */
+	int range_min[MAX_TS_FILTER_COORDS];	/* min computed ranges */
+
+	int tries_left;		/* We finish if we don't get enough samples */
+};
+
+extern struct ts_filter_api ts_filter_group_api;
+
+#endif

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