drivers/media/rc/ir-rc6-decoder.c

   1 /* ir-rc6-decoder.c - A decoder for the RC6 IR protocol
   2  *
   3  * Copyright (C) 2010 by David Härdeman <david@hardeman.nu>
   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 #include "rc-core-priv.h"
  16
  17 /*
  18  * This decoder currently supports:
  19  * RC6-0-16     (standard toggle bit in header)
  20  * RC6-6A-24    (no toggle bit)
  21  * RC6-6A-32    (MCE version with toggle bit in body)
  22  */
  23
  24 #define RC6_UNIT                444444  /* us */
  25 #define RC6_HEADER_NBITS        4       /* not including toggle bit */
  26 #define RC6_0_NBITS             16
  27 #define RC6_6A_SMALL_NBITS      24
  28 #define RC6_6A_LARGE_NBITS      32
  29 #define RC6_PREFIX_PULSE        (6 * RC6_UNIT)
  30 #define RC6_PREFIX_SPACE        (2 * RC6_UNIT)
  31 #define RC6_BIT_START           (1 * RC6_UNIT)
  32 #define RC6_BIT_END             (1 * RC6_UNIT)
  33 #define RC6_TOGGLE_START        (2 * RC6_UNIT)
  34 #define RC6_TOGGLE_END          (2 * RC6_UNIT)
  35 #define RC6_MODE_MASK           0x07    /* for the header bits */
  36 #define RC6_STARTBIT_MASK       0x08    /* for the header bits */
  37 #define RC6_6A_MCE_TOGGLE_MASK  0x8000  /* for the body bits */
  38
  39 enum rc6_mode {
  40         RC6_MODE_0,
  41         RC6_MODE_6A,
  42         RC6_MODE_UNKNOWN,
  43 };
  44
  45 enum rc6_state {
  46         STATE_INACTIVE,
  47         STATE_PREFIX_SPACE,
  48         STATE_HEADER_BIT_START,
  49         STATE_HEADER_BIT_END,
  50         STATE_TOGGLE_START,
  51         STATE_TOGGLE_END,
  52         STATE_BODY_BIT_START,
  53         STATE_BODY_BIT_END,
  54         STATE_FINISHED,
  55 };
  56
  57 static enum rc6_mode rc6_mode(struct rc6_dec *data)
  58 {
  59         switch (data->header & RC6_MODE_MASK) {
  60         case 0:
  61                 return RC6_MODE_0;
  62         case 6:
  63                 if (!data->toggle)
  64                         return RC6_MODE_6A;
  65                 /* fall through */
  66         default:
  67                 return RC6_MODE_UNKNOWN;
  68         }
  69 }
  70
  71 /**
  72  * ir_rc6_decode() - Decode one RC6 pulse or space
  73  * @dev:        the struct rc_dev descriptor of the device
  74  * @ev:         the struct ir_raw_event descriptor of the pulse/space
  75  *
  76  * This function returns -EINVAL if the pulse violates the state machine
  77  */
  78 static int ir_rc6_decode(struct rc_dev *dev, struct ir_raw_event ev)
  79 {
  80         struct rc6_dec *data = &dev->raw->rc6;
  81         u32 scancode;
  82         u8 toggle;
  83
  84         if (!(dev->raw->enabled_protocols & RC_TYPE_RC6))
  85                 return 0;
  86
  87         if (!is_timing_event(ev)) {
  88                 if (ev.reset)
  89                         data->state = STATE_INACTIVE;
  90                 return 0;
  91         }
  92
  93         if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
  94                 goto out;
  95
  96 again:
  97         IR_dprintk(2, "RC6 decode started at state %i (%uus %s)\n",
  98                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
  99
 100         if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
 101                 return 0;
 102
 103         switch (data->state) {
 104
 105         case STATE_INACTIVE:
 106                 if (!ev.pulse)
 107                         break;
 108
 109                 /* Note: larger margin on first pulse since each RC6_UNIT
 110                    is quite short and some hardware takes some time to
 111                    adjust to the signal */
 112                 if (!eq_margin(ev.duration, RC6_PREFIX_PULSE, RC6_UNIT))
 113                         break;
 114
 115                 data->state = STATE_PREFIX_SPACE;
 116                 data->count = 0;
 117                 return 0;
 118
 119         case STATE_PREFIX_SPACE:
 120                 if (ev.pulse)
 121                         break;
 122
 123                 if (!eq_margin(ev.duration, RC6_PREFIX_SPACE, RC6_UNIT / 2))
 124                         break;
 125
 126                 data->state = STATE_HEADER_BIT_START;
 127                 return 0;
 128
 129         case STATE_HEADER_BIT_START:
 130                 if (!eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2))
 131                         break;
 132
 133                 data->header <<= 1;
 134                 if (ev.pulse)
 135                         data->header |= 1;
 136                 data->count++;
 137                 data->state = STATE_HEADER_BIT_END;
 138                 return 0;
 139
 140         case STATE_HEADER_BIT_END:
 141                 if (!is_transition(&ev, &dev->raw->prev_ev))
 142                         break;
 143
 144                 if (data->count == RC6_HEADER_NBITS)
 145                         data->state = STATE_TOGGLE_START;
 146                 else
 147                         data->state = STATE_HEADER_BIT_START;
 148
 149                 decrease_duration(&ev, RC6_BIT_END);
 150                 goto again;
 151
 152         case STATE_TOGGLE_START:
 153                 if (!eq_margin(ev.duration, RC6_TOGGLE_START, RC6_UNIT / 2))
 154                         break;
 155
 156                 data->toggle = ev.pulse;
 157                 data->state = STATE_TOGGLE_END;
 158                 return 0;
 159
 160         case STATE_TOGGLE_END:
 161                 if (!is_transition(&ev, &dev->raw->prev_ev) ||
 162                     !geq_margin(ev.duration, RC6_TOGGLE_END, RC6_UNIT / 2))
 163                         break;
 164
 165                 if (!(data->header & RC6_STARTBIT_MASK)) {
 166                         IR_dprintk(1, "RC6 invalid start bit\n");
 167                         break;
 168                 }
 169
 170                 data->state = STATE_BODY_BIT_START;
 171                 decrease_duration(&ev, RC6_TOGGLE_END);
 172                 data->count = 0;
 173
 174                 switch (rc6_mode(data)) {
 175                 case RC6_MODE_0:
 176                         data->wanted_bits = RC6_0_NBITS;
 177                         break;
 178                 case RC6_MODE_6A:
 179                         /* This might look weird, but we basically
 180                            check the value of the first body bit to
 181                            determine the number of bits in mode 6A */
 182                         if ((!ev.pulse && !geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2)) ||
 183                             geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
 184                                 data->wanted_bits = RC6_6A_LARGE_NBITS;
 185                         else
 186                                 data->wanted_bits = RC6_6A_SMALL_NBITS;
 187                         break;
 188                 default:
 189                         IR_dprintk(1, "RC6 unknown mode\n");
 190                         goto out;
 191                 }
 192                 goto again;
 193
 194         case STATE_BODY_BIT_START:
 195                 if (!eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2))
 196                         break;
 197
 198                 data->body <<= 1;
 199                 if (ev.pulse)
 200                         data->body |= 1;
 201                 data->count++;
 202                 data->state = STATE_BODY_BIT_END;
 203                 return 0;
 204
 205         case STATE_BODY_BIT_END:
 206                 if (!is_transition(&ev, &dev->raw->prev_ev))
 207                         break;
 208
 209                 if (data->count == data->wanted_bits)
 210                         data->state = STATE_FINISHED;
 211                 else
 212                         data->state = STATE_BODY_BIT_START;
 213
 214                 decrease_duration(&ev, RC6_BIT_END);
 215                 goto again;
 216
 217         case STATE_FINISHED:
 218                 if (ev.pulse)
 219                         break;
 220
 221                 switch (rc6_mode(data)) {
 222                 case RC6_MODE_0:
 223                         scancode = data->body & 0xffff;
 224                         toggle = data->toggle;
 225                         IR_dprintk(1, "RC6(0) scancode 0x%04x (toggle: %u)\n",
 226                                    scancode, toggle);
 227                         break;
 228                 case RC6_MODE_6A:
 229                         if (data->wanted_bits == RC6_6A_LARGE_NBITS) {
 230                                 toggle = data->body & RC6_6A_MCE_TOGGLE_MASK ? 1 : 0;
 231                                 scancode = data->body & ~RC6_6A_MCE_TOGGLE_MASK;
 232                         } else {
 233                                 toggle = 0;
 234                                 scancode = data->body & 0xffffff;
 235                         }
 236
 237                         IR_dprintk(1, "RC6(6A) scancode 0x%08x (toggle: %u)\n",
 238                                    scancode, toggle);
 239                         break;
 240                 default:
 241                         IR_dprintk(1, "RC6 unknown mode\n");
 242                         goto out;
 243                 }
 244
 245                 rc_keydown(dev, scancode, toggle);
 246                 data->state = STATE_INACTIVE;
 247                 return 0;
 248         }
 249
 250 out:
 251         IR_dprintk(1, "RC6 decode failed at state %i (%uus %s)\n",
 252                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 253         data->state = STATE_INACTIVE;
 254         return -EINVAL;
 255 }
 256
 257 static struct ir_raw_handler rc6_handler = {
 258         .protocols      = RC_TYPE_RC6,
 259         .decode         = ir_rc6_decode,
 260 };
 261
 262 static int __init ir_rc6_decode_init(void)
 263 {
 264         ir_raw_handler_register(&rc6_handler);
 265
 266         printk(KERN_INFO "IR RC6 protocol handler initialized\n");
 267         return 0;
 268 }
 269
 270 static void __exit ir_rc6_decode_exit(void)
 271 {
 272         ir_raw_handler_unregister(&rc6_handler);
 273 }
 274
 275 module_init(ir_rc6_decode_init);
 276 module_exit(ir_rc6_decode_exit);
 277
 278 MODULE_LICENSE("GPL");
 279 MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
 280 MODULE_DESCRIPTION("RC6 IR protocol decoder");