drivers/media/rc/ir-rc5-decoder.c

   1 /* ir-rc5-decoder.c - handle RC5(x) IR Pulse/Space protocol
   2  *
   3  * Copyright (C) 2010 by Mauro Carvalho Chehab
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation version 2 of the License.
   8  *
   9  *  This program is distributed in the hope that it will be useful,
  10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  *  GNU General Public License for more details.
  13  */
  14
  15 /*
  16  * This code handles 14 bits RC5 protocols and 20 bits RC5x protocols.
  17  * There are other variants that use a different number of bits.
  18  * This is currently unsupported.
  19  * It considers a carrier of 36 kHz, with a total of 14/20 bits, where
  20  * the first two bits are start bits, and a third one is a filing bit
  21  */
  22
  23 #include "rc-core-priv.h"
  24 #include <linux/module.h>
  25
  26 #define RC5_NBITS               14
  27 #define RC5X_NBITS              20
  28 #define CHECK_RC5X_NBITS        8
  29 #define RC5_UNIT                888888 /* ns */
  30 #define RC5_BIT_START           (1 * RC5_UNIT)
  31 #define RC5_BIT_END             (1 * RC5_UNIT)
  32 #define RC5X_SPACE              (4 * RC5_UNIT)
  33
  34 enum rc5_state {
  35         STATE_INACTIVE,
  36         STATE_BIT_START,
  37         STATE_BIT_END,
  38         STATE_CHECK_RC5X,
  39         STATE_FINISHED,
  40 };
  41
  42 /**
  43  * ir_rc5_decode() - Decode one RC-5 pulse or space
  44  * @dev:        the struct rc_dev descriptor of the device
  45  * @ev:         the struct ir_raw_event descriptor of the pulse/space
  46  *
  47  * This function returns -EINVAL if the pulse violates the state machine
  48  */
  49 static int ir_rc5_decode(struct rc_dev *dev, struct ir_raw_event ev)
  50 {
  51         struct rc5_dec *data = &dev->raw->rc5;
  52         u8 toggle;
  53         u32 scancode;
  54
  55         if (!rc_protocols_enabled(dev, RC_BIT_RC5 | RC_BIT_RC5X))
  56                 return 0;
  57
  58         if (!is_timing_event(ev)) {
  59                 if (ev.reset)
  60                         data->state = STATE_INACTIVE;
  61                 return 0;
  62         }
  63
  64         if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
  65                 goto out;
  66
  67 again:
  68         IR_dprintk(2, "RC5(x) decode started at state %i (%uus %s)\n",
  69                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
  70
  71         if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
  72                 return 0;
  73
  74         switch (data->state) {
  75
  76         case STATE_INACTIVE:
  77                 if (!ev.pulse)
  78                         break;
  79
  80                 data->state = STATE_BIT_START;
  81                 data->count = 1;
  82                 /* We just need enough bits to get to STATE_CHECK_RC5X */
  83                 data->wanted_bits = RC5X_NBITS;
  84                 decrease_duration(&ev, RC5_BIT_START);
  85                 goto again;
  86
  87         case STATE_BIT_START:
  88                 if (!eq_margin(ev.duration, RC5_BIT_START, RC5_UNIT / 2))
  89                         break;
  90
  91                 data->bits <<= 1;
  92                 if (!ev.pulse)
  93                         data->bits |= 1;
  94                 data->count++;
  95                 data->state = STATE_BIT_END;
  96                 return 0;
  97
  98         case STATE_BIT_END:
  99                 if (!is_transition(&ev, &dev->raw->prev_ev))
 100                         break;
 101
 102                 if (data->count == data->wanted_bits)
 103                         data->state = STATE_FINISHED;
 104                 else if (data->count == CHECK_RC5X_NBITS)
 105                         data->state = STATE_CHECK_RC5X;
 106                 else
 107                         data->state = STATE_BIT_START;
 108
 109                 decrease_duration(&ev, RC5_BIT_END);
 110                 goto again;
 111
 112         case STATE_CHECK_RC5X:
 113                 if (!ev.pulse && geq_margin(ev.duration, RC5X_SPACE, RC5_UNIT / 2)) {
 114                         /* RC5X */
 115                         data->wanted_bits = RC5X_NBITS;
 116                         decrease_duration(&ev, RC5X_SPACE);
 117                 } else {
 118                         /* RC5 */
 119                         data->wanted_bits = RC5_NBITS;
 120                 }
 121                 data->state = STATE_BIT_START;
 122                 goto again;
 123
 124         case STATE_FINISHED:
 125                 if (ev.pulse)
 126                         break;
 127
 128                 if (data->wanted_bits == RC5X_NBITS) {
 129                         /* RC5X */
 130                         u8 xdata, command, system;
 131                         if (!rc_protocols_enabled(dev, RC_BIT_RC5X)) {
 132                                 data->state = STATE_INACTIVE;
 133                                 return 0;
 134                         }
 135                         xdata    = (data->bits & 0x0003F) >> 0;
 136                         command  = (data->bits & 0x00FC0) >> 6;
 137                         system   = (data->bits & 0x1F000) >> 12;
 138                         toggle   = (data->bits & 0x20000) ? 1 : 0;
 139                         command += (data->bits & 0x01000) ? 0 : 0x40;
 140                         scancode = system << 16 | command << 8 | xdata;
 141
 142                         IR_dprintk(1, "RC5X scancode 0x%06x (toggle: %u)\n",
 143                                    scancode, toggle);
 144
 145                 } else {
 146                         /* RC5 */
 147                         u8 command, system;
 148                         if (!rc_protocols_enabled(dev, RC_BIT_RC5)) {
 149                                 data->state = STATE_INACTIVE;
 150                                 return 0;
 151                         }
 152                         command  = (data->bits & 0x0003F) >> 0;
 153                         system   = (data->bits & 0x007C0) >> 6;
 154                         toggle   = (data->bits & 0x00800) ? 1 : 0;
 155                         command += (data->bits & 0x01000) ? 0 : 0x40;
 156                         scancode = system << 8 | command;
 157
 158                         IR_dprintk(1, "RC5 scancode 0x%04x (toggle: %u)\n",
 159                                    scancode, toggle);
 160                 }
 161
 162                 rc_keydown(dev, scancode, toggle);
 163                 data->state = STATE_INACTIVE;
 164                 return 0;
 165         }
 166
 167 out:
 168         IR_dprintk(1, "RC5(x) decode failed at state %i (%uus %s)\n",
 169                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 170         data->state = STATE_INACTIVE;
 171         return -EINVAL;
 172 }
 173
 174 static struct ir_raw_handler rc5_handler = {
 175         .protocols      = RC_BIT_RC5 | RC_BIT_RC5X,
 176         .decode         = ir_rc5_decode,
 177 };
 178
 179 static int __init ir_rc5_decode_init(void)
 180 {
 181         ir_raw_handler_register(&rc5_handler);
 182
 183         printk(KERN_INFO "IR RC5(x) protocol handler initialized\n");
 184         return 0;
 185 }
 186
 187 static void __exit ir_rc5_decode_exit(void)
 188 {
 189         ir_raw_handler_unregister(&rc5_handler);
 190 }
 191
 192 module_init(ir_rc5_decode_init);
 193 module_exit(ir_rc5_decode_exit);
 194
 195 MODULE_LICENSE("GPL");
 196 MODULE_AUTHOR("Mauro Carvalho Chehab");
 197 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 198 MODULE_DESCRIPTION("RC5(x) IR protocol decoder");