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 #include <linux/module.h>
  17
  18 /*
  19  * This decoder currently supports:
  20  * RC6-0-16     (standard toggle bit in header)
  21  * RC6-6A-20    (no toggle bit)
  22  * RC6-6A-24    (no toggle bit)
  23  * RC6-6A-32    (MCE version with toggle bit in body)
  24  */
  25
  26 #define RC6_UNIT                444444  /* nanosecs */
  27 #define RC6_HEADER_NBITS        4       /* not including toggle bit */
  28 #define RC6_0_NBITS             16
  29 #define RC6_6A_32_NBITS         32
  30 #define RC6_6A_NBITS            128     /* Variable 8..128 */
  31 #define RC6_PREFIX_PULSE        (6 * RC6_UNIT)
  32 #define RC6_PREFIX_SPACE        (2 * RC6_UNIT)
  33 #define RC6_BIT_START           (1 * RC6_UNIT)
  34 #define RC6_BIT_END             (1 * RC6_UNIT)
  35 #define RC6_TOGGLE_START        (2 * RC6_UNIT)
  36 #define RC6_TOGGLE_END          (2 * RC6_UNIT)
  37 #define RC6_SUFFIX_SPACE        (6 * RC6_UNIT)
  38 #define RC6_MODE_MASK           0x07    /* for the header bits */
  39 #define RC6_STARTBIT_MASK       0x08    /* for the header bits */
  40 #define RC6_6A_MCE_TOGGLE_MASK  0x8000  /* for the body bits */
  41 #define RC6_6A_LCC_MASK         0xffff0000 /* RC6-6A-32 long customer code mask */
  42 #define RC6_6A_MCE_CC           0x800f0000 /* MCE customer code */
  43 #ifndef CHAR_BIT
  44 #define CHAR_BIT 8      /* Normally in <limits.h> */
  45 #endif
  46
  47 enum rc6_mode {
  48         RC6_MODE_0,
  49         RC6_MODE_6A,
  50         RC6_MODE_UNKNOWN,
  51 };
  52
  53 enum rc6_state {
  54         STATE_INACTIVE,
  55         STATE_PREFIX_SPACE,
  56         STATE_HEADER_BIT_START,
  57         STATE_HEADER_BIT_END,
  58         STATE_TOGGLE_START,
  59         STATE_TOGGLE_END,
  60         STATE_BODY_BIT_START,
  61         STATE_BODY_BIT_END,
  62         STATE_FINISHED,
  63 };
  64
  65 static enum rc6_mode rc6_mode(struct rc6_dec *data)
  66 {
  67         switch (data->header & RC6_MODE_MASK) {
  68         case 0:
  69                 return RC6_MODE_0;
  70         case 6:
  71                 if (!data->toggle)
  72                         return RC6_MODE_6A;
  73                 /* fall through */
  74         default:
  75                 return RC6_MODE_UNKNOWN;
  76         }
  77 }
  78
  79 /**
  80  * ir_rc6_decode() - Decode one RC6 pulse or space
  81  * @dev:        the struct rc_dev descriptor of the device
  82  * @ev:         the struct ir_raw_event descriptor of the pulse/space
  83  *
  84  * This function returns -EINVAL if the pulse violates the state machine
  85  */
  86 static int ir_rc6_decode(struct rc_dev *dev, struct ir_raw_event ev)
  87 {
  88         struct rc6_dec *data = &dev->raw->rc6;
  89         u32 scancode;
  90         u8 toggle;
  91         enum rc_proto protocol;
  92
  93         if (!is_timing_event(ev)) {
  94                 if (ev.reset)
  95                         data->state = STATE_INACTIVE;
  96                 return 0;
  97         }
  98
  99         if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
 100                 goto out;
 101
 102 again:
 103         dev_dbg(&dev->dev, "RC6 decode started at state %i (%uus %s)\n",
 104                 data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 105
 106         if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
 107                 return 0;
 108
 109         switch (data->state) {
 110
 111         case STATE_INACTIVE:
 112                 if (!ev.pulse)
 113                         break;
 114
 115                 /* Note: larger margin on first pulse since each RC6_UNIT
 116                    is quite short and some hardware takes some time to
 117                    adjust to the signal */
 118                 if (!eq_margin(ev.duration, RC6_PREFIX_PULSE, RC6_UNIT))
 119                         break;
 120
 121                 data->state = STATE_PREFIX_SPACE;
 122                 data->count = 0;
 123                 return 0;
 124
 125         case STATE_PREFIX_SPACE:
 126                 if (ev.pulse)
 127                         break;
 128
 129                 if (!eq_margin(ev.duration, RC6_PREFIX_SPACE, RC6_UNIT / 2))
 130                         break;
 131
 132                 data->state = STATE_HEADER_BIT_START;
 133                 data->header = 0;
 134                 return 0;
 135
 136         case STATE_HEADER_BIT_START:
 137                 if (!eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2))
 138                         break;
 139
 140                 data->header <<= 1;
 141                 if (ev.pulse)
 142                         data->header |= 1;
 143                 data->count++;
 144                 data->state = STATE_HEADER_BIT_END;
 145                 return 0;
 146
 147         case STATE_HEADER_BIT_END:
 148                 if (data->count == RC6_HEADER_NBITS)
 149                         data->state = STATE_TOGGLE_START;
 150                 else
 151                         data->state = STATE_HEADER_BIT_START;
 152
 153                 decrease_duration(&ev, RC6_BIT_END);
 154                 goto again;
 155
 156         case STATE_TOGGLE_START:
 157                 if (!eq_margin(ev.duration, RC6_TOGGLE_START, RC6_UNIT / 2))
 158                         break;
 159
 160                 data->toggle = ev.pulse;
 161                 data->state = STATE_TOGGLE_END;
 162                 return 0;
 163
 164         case STATE_TOGGLE_END:
 165                 if (!(data->header & RC6_STARTBIT_MASK)) {
 166                         dev_dbg(&dev->dev, "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                 data->body = 0;
 174
 175                 switch (rc6_mode(data)) {
 176                 case RC6_MODE_0:
 177                         data->wanted_bits = RC6_0_NBITS;
 178                         break;
 179                 case RC6_MODE_6A:
 180                         data->wanted_bits = RC6_6A_NBITS;
 181                         break;
 182                 default:
 183                         dev_dbg(&dev->dev, "RC6 unknown mode\n");
 184                         goto out;
 185                 }
 186                 goto again;
 187
 188         case STATE_BODY_BIT_START:
 189                 if (eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2)) {
 190                         /* Discard LSB's that won't fit in data->body */
 191                         if (data->count++ < CHAR_BIT * sizeof data->body) {
 192                                 data->body <<= 1;
 193                                 if (ev.pulse)
 194                                         data->body |= 1;
 195                         }
 196                         data->state = STATE_BODY_BIT_END;
 197                         return 0;
 198                 } else if (RC6_MODE_6A == rc6_mode(data) && !ev.pulse &&
 199                                 geq_margin(ev.duration, RC6_SUFFIX_SPACE, RC6_UNIT / 2)) {
 200                         data->state = STATE_FINISHED;
 201                         goto again;
 202                 }
 203                 break;
 204
 205         case STATE_BODY_BIT_END:
 206                 if (data->count == data->wanted_bits)
 207                         data->state = STATE_FINISHED;
 208                 else
 209                         data->state = STATE_BODY_BIT_START;
 210
 211                 decrease_duration(&ev, RC6_BIT_END);
 212                 goto again;
 213
 214         case STATE_FINISHED:
 215                 if (ev.pulse)
 216                         break;
 217
 218                 switch (rc6_mode(data)) {
 219                 case RC6_MODE_0:
 220                         scancode = data->body;
 221                         toggle = data->toggle;
 222                         protocol = RC_PROTO_RC6_0;
 223                         dev_dbg(&dev->dev, "RC6(0) scancode 0x%04x (toggle: %u)\n",
 224                                 scancode, toggle);
 225                         break;
 226
 227                 case RC6_MODE_6A:
 228                         if (data->count > CHAR_BIT * sizeof data->body) {
 229                                 dev_dbg(&dev->dev, "RC6 too many (%u) data bits\n",
 230                                         data->count);
 231                                 goto out;
 232                         }
 233
 234                         scancode = data->body;
 235                         switch (data->count) {
 236                         case 20:
 237                                 protocol = RC_PROTO_RC6_6A_20;
 238                                 toggle = 0;
 239                                 break;
 240                         case 24:
 241                                 protocol = RC_PROTO_RC6_6A_24;
 242                                 toggle = 0;
 243                                 break;
 244                         case 32:
 245                                 if ((scancode & RC6_6A_LCC_MASK) == RC6_6A_MCE_CC) {
 246                                         protocol = RC_PROTO_RC6_MCE;
 247                                         toggle = !!(scancode & RC6_6A_MCE_TOGGLE_MASK);
 248                                         scancode &= ~RC6_6A_MCE_TOGGLE_MASK;
 249                                 } else {
 250                                         protocol = RC_PROTO_RC6_6A_32;
 251                                         toggle = 0;
 252                                 }
 253                                 break;
 254                         default:
 255                                 dev_dbg(&dev->dev, "RC6(6A) unsupported length\n");
 256                                 goto out;
 257                         }
 258
 259                         dev_dbg(&dev->dev, "RC6(6A) proto 0x%04x, scancode 0x%08x (toggle: %u)\n",
 260                                 protocol, scancode, toggle);
 261                         break;
 262                 default:
 263                         dev_dbg(&dev->dev, "RC6 unknown mode\n");
 264                         goto out;
 265                 }
 266
 267                 rc_keydown(dev, protocol, scancode, toggle);
 268                 data->state = STATE_INACTIVE;
 269                 return 0;
 270         }
 271
 272 out:
 273         dev_dbg(&dev->dev, "RC6 decode failed at state %i (%uus %s)\n",
 274                 data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 275         data->state = STATE_INACTIVE;
 276         return -EINVAL;
 277 }
 278
 279 static const struct ir_raw_timings_manchester ir_rc6_timings[4] = {
 280         {
 281                 .leader_pulse           = RC6_PREFIX_PULSE,
 282                 .leader_space           = RC6_PREFIX_SPACE,
 283                 .clock                  = RC6_UNIT,
 284                 .invert                 = 1,
 285         },
 286         {
 287                 .clock                  = RC6_UNIT * 2,
 288                 .invert                 = 1,
 289         },
 290         {
 291                 .clock                  = RC6_UNIT,
 292                 .invert                 = 1,
 293                 .trailer_space          = RC6_SUFFIX_SPACE,
 294         },
 295 };
 296
 297 /**
 298  * ir_rc6_encode() - Encode a scancode as a stream of raw events
 299  *
 300  * @protocol:   protocol to encode
 301  * @scancode:   scancode to encode
 302  * @events:     array of raw ir events to write into
 303  * @max:        maximum size of @events
 304  *
 305  * Returns:     The number of events written.
 306  *              -ENOBUFS if there isn't enough space in the array to fit the
 307  *              encoding. In this case all @max events will have been written.
 308  *              -EINVAL if the scancode is ambiguous or invalid.
 309  */
 310 static int ir_rc6_encode(enum rc_proto protocol, u32 scancode,
 311                          struct ir_raw_event *events, unsigned int max)
 312 {
 313         int ret;
 314         struct ir_raw_event *e = events;
 315
 316         if (protocol == RC_PROTO_RC6_0) {
 317                 /* Modulate the header (Start Bit & Mode-0) */
 318                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 319                                             &ir_rc6_timings[0],
 320                                             RC6_HEADER_NBITS, (1 << 3));
 321                 if (ret < 0)
 322                         return ret;
 323
 324                 /* Modulate Trailer Bit */
 325                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 326                                             &ir_rc6_timings[1], 1, 0);
 327                 if (ret < 0)
 328                         return ret;
 329
 330                 /* Modulate rest of the data */
 331                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 332                                             &ir_rc6_timings[2], RC6_0_NBITS,
 333                                             scancode);
 334                 if (ret < 0)
 335                         return ret;
 336
 337         } else {
 338                 int bits;
 339
 340                 switch (protocol) {
 341                 case RC_PROTO_RC6_MCE:
 342                 case RC_PROTO_RC6_6A_32:
 343                         bits = 32;
 344                         break;
 345                 case RC_PROTO_RC6_6A_24:
 346                         bits = 24;
 347                         break;
 348                 case RC_PROTO_RC6_6A_20:
 349                         bits = 20;
 350                         break;
 351                 default:
 352                         return -EINVAL;
 353                 }
 354
 355                 /* Modulate the header (Start Bit & Header-version 6 */
 356                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 357                                             &ir_rc6_timings[0],
 358                                             RC6_HEADER_NBITS, (1 << 3 | 6));
 359                 if (ret < 0)
 360                         return ret;
 361
 362                 /* Modulate Trailer Bit */
 363                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 364                                             &ir_rc6_timings[1], 1, 0);
 365                 if (ret < 0)
 366                         return ret;
 367
 368                 /* Modulate rest of the data */
 369                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 370                                             &ir_rc6_timings[2],
 371                                             bits,
 372                                             scancode);
 373                 if (ret < 0)
 374                         return ret;
 375         }
 376
 377         return e - events;
 378 }
 379
 380 static struct ir_raw_handler rc6_handler = {
 381         .protocols      = RC_PROTO_BIT_RC6_0 | RC_PROTO_BIT_RC6_6A_20 |
 382                           RC_PROTO_BIT_RC6_6A_24 | RC_PROTO_BIT_RC6_6A_32 |
 383                           RC_PROTO_BIT_RC6_MCE,
 384         .decode         = ir_rc6_decode,
 385         .encode         = ir_rc6_encode,
 386         .carrier        = 36000,
 387         .min_timeout    = RC6_SUFFIX_SPACE,
 388 };
 389
 390 static int __init ir_rc6_decode_init(void)
 391 {
 392         ir_raw_handler_register(&rc6_handler);
 393
 394         printk(KERN_INFO "IR RC6 protocol handler initialized\n");
 395         return 0;
 396 }
 397
 398 static void __exit ir_rc6_decode_exit(void)
 399 {
 400         ir_raw_handler_unregister(&rc6_handler);
 401 }
 402
 403 module_init(ir_rc6_decode_init);
 404 module_exit(ir_rc6_decode_exit);
 405
 406 MODULE_LICENSE("GPL");
 407 MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
 408 MODULE_DESCRIPTION("RC6 IR protocol decoder");