drivers/input/touchscreen/ts_filter_median.c

   1 /*
   2  * This program is free software; you can redistribute it and/or modify
   3  * it under the terms of the GNU General Public License as published by
   4  * the Free Software Foundation; either version 2 of the License, or
   5  * (at your option) any later version.
   6  *
   7  * This program is distributed in the hope that it will be useful,
   8  * but WITHOUT ANY WARRANTY; without even the implied warranty of
   9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10  * GNU General Public License for more details.
  11  *
  12  * You should have received a copy of the GNU General Public License
  13  * along with this program; if not, write to the Free Software
  14  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  15  *
  16  * Copyright (c) 2008 Andy Green <andy@openmoko.com>
  17  *
  18  *
  19  * Median averaging stuff.  We sort incoming raw samples into an array of
  20  * MEDIAN_SIZE length, discarding the oldest sample each time once we are full.
  21  * We then return the sum of the middle three samples for X and Y.  It means
  22  * the final result must be divided by (3 * scaling factor) to correct for
  23  * avoiding the repeated /3.
  24  *
  25  * This strongly rejects brief excursions away from a central point that is
  26  * sticky in time compared to the excursion duration.
  27  *
  28  * Thanks to Dale Schumacher (who wrote some example code) and Carl-Daniel
  29  * Halifinger who pointed out this would be a good method.
  30  */
  31
  32 #include <linux/errno.h>
  33 #include <linux/kernel.h>
  34 #include <linux/slab.h>
  35 #include "ts_filter_median.h"
  36
  37 static void ts_filter_median_insert(int *p, int sample, int count)
  38 {
  39         int n;
  40
  41         /* search through what we got so far to find where to put sample */
  42         for (n = 0; n < count; n++)
  43                  /* we met somebody bigger than us? */
  44                 if (sample < p[n]) {
  45                         /* starting from the end, push bigger guys down one */
  46                         for (count--; count >= n; count--)
  47                                 p[count + 1] = p[count];
  48                         p[n] = sample; /* and put us in place of first bigger */
  49                         return;
  50                 }
  51
  52         p[count] = sample; /* nobody was bigger than us, add us on the end */
  53 }
  54
  55 static void ts_filter_median_del(int *p, int value, int count)
  56 {
  57         int index;
  58
  59         for (index = 0; index < count; index++)
  60                 if (p[index] == value) {
  61                         for (; index < count; index++)
  62                                 p[index] = p[index + 1];
  63                         return;
  64                 }
  65 }
  66
  67
  68 static void ts_filter_median_clear_internal(struct ts_filter *tsf)
  69 {
  70         struct ts_filter_median *tsfm = (struct ts_filter_median *)tsf;
  71
  72         tsfm->pos = 0;
  73         tsfm->valid = 0;
  74
  75 }
  76 static void ts_filter_median_clear(struct ts_filter *tsf)
  77 {
  78         ts_filter_median_clear_internal(tsf);
  79
  80         if (tsf->next) /* chain */
  81                 (tsf->next->api->clear)(tsf->next);
  82 }
  83
  84 static struct ts_filter *ts_filter_median_create(struct platform_device *pdev,
  85                                                  void *conf, int count_coords)
  86 {
  87         int *p;
  88         int n;
  89         struct ts_filter_median *tsfm = kzalloc(sizeof(struct ts_filter_median),
  90                                                                     GFP_KERNEL);
  91
  92         if (!tsfm)
  93                 return NULL;
  94
  95         tsfm->config = (struct ts_filter_median_configuration *)conf;
  96         BUG_ON((count_coords < 1) || (count_coords > MAX_TS_FILTER_COORDS));
  97         tsfm->tsf.count_coords = count_coords;
  98
  99         tsfm->config->midpoint = (tsfm->config->extent >> 1) + 1;
 100
 101         p = kmalloc(2 * count_coords * sizeof(int) * (tsfm->config->extent + 1),
 102                                                                     GFP_KERNEL);
 103         if (!p) {
 104                 kfree(tsfm);
 105                 return NULL;
 106         }
 107
 108         for (n = 0; n < count_coords; n++) {
 109                 tsfm->sort[n] = p;
 110                 p += tsfm->config->extent + 1;
 111                 tsfm->fifo[n] = p;
 112                 p += tsfm->config->extent + 1;
 113         }
 114
 115         ts_filter_median_clear_internal(&tsfm->tsf);
 116
 117         printk(KERN_INFO"  Created Median ts filter len %d depth %d dec %d\n",
 118                tsfm->config->extent, count_coords,
 119                tsfm->config->decimation_threshold);
 120
 121         return &tsfm->tsf;
 122 }
 123
 124 static void ts_filter_median_destroy(struct platform_device *pdev,
 125                                      struct ts_filter *tsf)
 126 {
 127         struct ts_filter_median *tsfm = (struct ts_filter_median *)tsf;
 128
 129         kfree(tsfm->sort[0]); /* first guy has pointer from kmalloc */
 130         kfree(tsf);
 131 }
 132
 133 static void ts_filter_median_scale(struct ts_filter *tsf, int *coords)
 134 {
 135         int n;
 136
 137         for (n = 0; n < tsf->count_coords; n++)
 138                 coords[n] = (coords[n] + 2) / 3;
 139
 140         if (tsf->next) /* chain */
 141                 (tsf->next->api->scale)(tsf->next, coords);
 142 }
 143
 144 /*
 145  * Give us the raw sample data coords, and if we return 1 then you can
 146  * get a filtered coordinate from coords. If we return 0 you didn't
 147  * fill all the filters with samples yet.
 148  */
 149
 150 static int ts_filter_median_process(struct ts_filter *tsf, int *coords)
 151 {
 152         struct ts_filter_median *tsfm = (struct ts_filter_median *)tsf;
 153         int n;
 154         int movement = 1;
 155
 156         for (n = 0; n < tsf->count_coords; n++) {
 157                 /* grab copy in insertion order to remove when oldest */
 158                 tsfm->fifo[n][tsfm->pos] = coords[n];
 159                 /* insert these samples in sorted order in the median arrays */
 160                 ts_filter_median_insert(tsfm->sort[n], coords[n], tsfm->valid);
 161         }
 162         /* move us on in the fifo */
 163         if (++tsfm->pos == (tsfm->config->extent + 1))
 164                 tsfm->pos = 0;
 165
 166         /* we have finished a median sampling? */
 167         if (++tsfm->valid != tsfm->config->extent)
 168                 return 0; /* no valid sample to use */
 169
 170         /* discard the oldest sample in median sorted array */
 171         tsfm->valid--;
 172
 173         /*
 174          * Sum the middle 3 in the median sorted arrays. We don't divide back
 175          * down which increases the sum resolution by a factor of 3 until the
 176          * scale API is called.
 177          */
 178         for (n = 0; n < tsfm->tsf.count_coords; n++)
 179                 /* perform the deletion of the oldest sample */
 180                 ts_filter_median_del(tsfm->sort[n], tsfm->fifo[n][tsfm->pos],
 181                                                                    tsfm->valid);
 182
 183         tsfm->decimation_count--;
 184         if (tsfm->decimation_count >= 0)
 185                 return 0;
 186
 187         for (n = 0; n < tsfm->tsf.count_coords; n++) {
 188                 /* give the coordinate result from summing median 3 */
 189                 coords[n] = tsfm->sort[n][tsfm->config->midpoint - 1] +
 190                             tsfm->sort[n][tsfm->config->midpoint] +
 191                             tsfm->sort[n][tsfm->config->midpoint + 1]
 192                         ;
 193
 194                 movement += abs(tsfm->last_issued[n] - coords[n]);
 195         }
 196
 197         if (movement > tsfm->config->decimation_threshold) /* fast */
 198                 tsfm->decimation_count = tsfm->config->decimation_above;
 199         else
 200                 tsfm->decimation_count = tsfm->config->decimation_below;
 201
 202         memcpy(&tsfm->last_issued[0], coords,
 203                tsfm->tsf.count_coords * sizeof(int));
 204
 205         if (tsf->next) /* chain */
 206                 return (tsf->next->api->process)(tsf->next, coords);
 207
 208         return 1;
 209 }
 210
 211 struct ts_filter_api ts_filter_median_api = {
 212         .create = ts_filter_median_create,
 213         .destroy = ts_filter_median_destroy,
 214         .clear = ts_filter_median_clear,
 215         .process = ts_filter_median_process,
 216         .scale = ts_filter_median_scale,
 217 };