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/*
* 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@freaks-unidos.net>
* All rights reserved.
*
* This filter is useful to reject clicks that are not reliable. We
* only care about what happens when we receive DOWN events for the fist time.
* If this filter does not reject the first samples then it will change
* its internal state to "passed" and the remaining samples
* will be passed to the next filter in the chain.
*
* First we collect N samples, then then we sort them. We discard the borders
* (with a window) and then compute the variance of the remaining set.
* If the computed variance is bigger than a threshold, we reject the click.
*
*/
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/sort.h>
#include <linux/ts_filter_variance.h>
static void ts_filter_variance_clear_internal(struct ts_filter_variance *tsfv,
int attempts)
{
tsfv->N = 0;
tsfv->passed = 0;
tsfv->tries_left = attempts;
}
static void ts_filter_variance_clear(struct ts_filter *tsf)
{
struct ts_filter_variance *tsfv = (struct ts_filter_variance *)tsf;
ts_filter_variance_clear_internal(tsfv, tsfv->config->attempts);
if (tsf->next) /* chain */
(tsf->next->api->clear)(tsf->next);
}
static struct ts_filter *ts_filter_variance_create(void *conf, int count_coords)
{
struct ts_filter_variance *tsfv;
int i;
BUG_ON((count_coords < 1) || (count_coords > MAX_TS_FILTER_COORDS));
tsfv = kzalloc(sizeof(struct ts_filter_variance), GFP_KERNEL);
if (!tsfv)
return NULL;
tsfv->config = (struct ts_filter_variance_configuration *)conf;
tsfv->tsf.count_coords = count_coords;
BUG_ON(tsfv->config->attempts <= 0);
tsfv->samples[0] = kmalloc(count_coords * sizeof(int) *
tsfv->config->extent, GFP_KERNEL);
if (!tsfv->samples[0]) {
kfree(tsfv);
return NULL;
}
for (i = 1; i < count_coords; ++i)
tsfv->samples[i] = tsfv->samples[0] + i * tsfv->config->extent;
ts_filter_variance_clear_internal(tsfv, tsfv->config->attempts);
printk(KERN_INFO" Created Variance ts filter len %d depth %d window"
" %d thresh %d\n", tsfv->config->extent,
count_coords, tsfv->config->window,
tsfv->config->threshold);
/* scale the threshold to avoid divisions later */
tsfv->config->threshold *= tsfv->config->extent -
(tsfv->config->window << 1);
return &tsfv->tsf;
}
static void ts_filter_variance_destroy(struct ts_filter *tsf)
{
struct ts_filter_variance *tsfv = (struct ts_filter_variance *)tsf;
kfree(tsfv->samples[0]); /* first guy has pointer from kmalloc */
kfree(tsf);
}
static void ts_filter_variance_scale(struct ts_filter *tsf, int *coords)
{
struct ts_filter_variance *tsfv = (struct ts_filter_variance *)tsf;
if (!tsfv->passed)
return;
if (tsf->next) {
(tsf->next->api->scale)(tsf->next, coords);
} else {
int n;
for (n = 0; n < tsf->count_coords; n++) {
int c = tsfv->samples[n][tsfv->N / 2] +
tsfv->samples[n][tsfv->N / 2 + 1] +
tsfv->samples[n][tsfv->N / 2 - 1];
coords[n] = (c + 2) / 3;
}
}
}
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;
}
/* give us the raw sample data coords, and if we return 1 then you can
* get a filtered coordinate from coords: if we return 0 you didn't
* fill all the filters with samples yet.
*/
static int ts_filter_variance_process(struct ts_filter *tsf, int *coords)
{
struct ts_filter_variance *tsfv = (struct ts_filter_variance *)tsf;
int n;
if (tsfv->passed) { /* chain */
if (tsf->next)
return (tsf->next->api->process)(tsf->next, coords);
return 1;
}
for (n = 0; n < tsf->count_coords; n++)
tsfv->samples[n][tsfv->N] = coords[n];
if (++tsfv->N < tsfv->config->extent)
return 0; /* we meed more samples */
tsfv->passed = 1;
for (n = 0; n < tsfv->tsf.count_coords; n++) {
int i;
int avg = 0;
int variance = 0;
sort(tsfv->samples[n], tsfv->config->extent, sizeof(int),
int_cmp, NULL);
for (i = tsfv->config->window; i < tsfv->config->extent -
tsfv->config->window; ++i)
avg += tsfv->samples[n][i];
avg /= tsfv->config->extent - (tsfv->config->window << 1);
for (i = tsfv->config->window; i < tsfv->config->extent -
tsfv->config->window; ++i) {
int s = tsfv->samples[n][i] - avg;
variance += s * s;
}
if (variance > tsfv->config->threshold) {
tsfv->passed = 0;
break;
}
}
if (tsfv->passed) /* Let's reuse the last sample */
return ts_filter_variance_process(tsf, coords);
if (--tsfv->tries_left) {
ts_filter_variance_clear_internal(tsfv, tsfv->tries_left);
return 0; /* ask for more samples */
}
/* avoid overflow if we are called again without clearing the filter */
ts_filter_variance_clear_internal(tsfv, tsfv->config->attempts);
return -1;
}
struct ts_filter_api ts_filter_variance_api = {
.create = ts_filter_variance_create,
.destroy = ts_filter_variance_destroy,
.clear = ts_filter_variance_clear,
.process = ts_filter_variance_process,
.scale = ts_filter_variance_scale,
};
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