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 #define RC6_6A_KATHREIN_CC      0x80460000 /* Kathrein RCU-676 customer code */
  44 #ifndef CHAR_BIT
  45 #define CHAR_BIT 8      /* Normally in <limits.h> */
  46 #endif
  47
  48 enum rc6_mode {
  49         RC6_MODE_0,
  50         RC6_MODE_6A,
  51         RC6_MODE_UNKNOWN,
  52 };
  53
  54 enum rc6_state {
  55         STATE_INACTIVE,
  56         STATE_PREFIX_SPACE,
  57         STATE_HEADER_BIT_START,
  58         STATE_HEADER_BIT_END,
  59         STATE_TOGGLE_START,
  60         STATE_TOGGLE_END,
  61         STATE_BODY_BIT_START,
  62         STATE_BODY_BIT_END,
  63         STATE_FINISHED,
  64 };
  65
  66 static enum rc6_mode rc6_mode(struct rc6_dec *data)
  67 {
  68         switch (data->header & RC6_MODE_MASK) {
  69         case 0:
  70                 return RC6_MODE_0;
  71         case 6:
  72                 if (!data->toggle)
  73                         return RC6_MODE_6A;
  74                 /* fall through */
  75         default:
  76                 return RC6_MODE_UNKNOWN;
  77         }
  78 }
  79
  80 /**
  81  * ir_rc6_decode() - Decode one RC6 pulse or space
  82  * @dev:        the struct rc_dev descriptor of the device
  83  * @ev:         the struct ir_raw_event descriptor of the pulse/space
  84  *
  85  * This function returns -EINVAL if the pulse violates the state machine
  86  */
  87 static int ir_rc6_decode(struct rc_dev *dev, struct ir_raw_event ev)
  88 {
  89         struct rc6_dec *data = &dev->raw->rc6;
  90         u32 scancode;
  91         u8 toggle;
  92         enum rc_proto protocol;
  93
  94         if (!is_timing_event(ev)) {
  95                 if (ev.reset)
  96                         data->state = STATE_INACTIVE;
  97                 return 0;
  98         }
  99
 100         if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
 101                 goto out;
 102
 103 again:
 104         IR_dprintk(2, "RC6 decode started at state %i (%uus %s)\n",
 105                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 106
 107         if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
 108                 return 0;
 109
 110         switch (data->state) {
 111
 112         case STATE_INACTIVE:
 113                 if (!ev.pulse)
 114                         break;
 115
 116                 /* Note: larger margin on first pulse since each RC6_UNIT
 117                    is quite short and some hardware takes some time to
 118                    adjust to the signal */
 119                 if (!eq_margin(ev.duration, RC6_PREFIX_PULSE, RC6_UNIT))
 120                         break;
 121
 122                 data->state = STATE_PREFIX_SPACE;
 123                 data->count = 0;
 124                 return 0;
 125
 126         case STATE_PREFIX_SPACE:
 127                 if (ev.pulse)
 128                         break;
 129
 130                 if (!eq_margin(ev.duration, RC6_PREFIX_SPACE, RC6_UNIT / 2))
 131                         break;
 132
 133                 data->state = STATE_HEADER_BIT_START;
 134                 data->header = 0;
 135                 return 0;
 136
 137         case STATE_HEADER_BIT_START:
 138                 if (!eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2))
 139                         break;
 140
 141                 data->header <<= 1;
 142                 if (ev.pulse)
 143                         data->header |= 1;
 144                 data->count++;
 145                 data->state = STATE_HEADER_BIT_END;
 146                 return 0;
 147
 148         case STATE_HEADER_BIT_END:
 149                 if (!is_transition(&ev, &dev->raw->prev_ev))
 150                         break;
 151
 152                 if (data->count == RC6_HEADER_NBITS)
 153                         data->state = STATE_TOGGLE_START;
 154                 else
 155                         data->state = STATE_HEADER_BIT_START;
 156
 157                 decrease_duration(&ev, RC6_BIT_END);
 158                 goto again;
 159
 160         case STATE_TOGGLE_START:
 161                 if (!eq_margin(ev.duration, RC6_TOGGLE_START, RC6_UNIT / 2))
 162                         break;
 163
 164                 data->toggle = ev.pulse;
 165                 data->state = STATE_TOGGLE_END;
 166                 return 0;
 167
 168         case STATE_TOGGLE_END:
 169                 if (!is_transition(&ev, &dev->raw->prev_ev) ||
 170                     !geq_margin(ev.duration, RC6_TOGGLE_END, RC6_UNIT / 2))
 171                         break;
 172
 173                 if (!(data->header & RC6_STARTBIT_MASK)) {
 174                         IR_dprintk(1, "RC6 invalid start bit\n");
 175                         break;
 176                 }
 177
 178                 data->state = STATE_BODY_BIT_START;
 179                 decrease_duration(&ev, RC6_TOGGLE_END);
 180                 data->count = 0;
 181                 data->body = 0;
 182
 183                 switch (rc6_mode(data)) {
 184                 case RC6_MODE_0:
 185                         data->wanted_bits = RC6_0_NBITS;
 186                         break;
 187                 case RC6_MODE_6A:
 188                         data->wanted_bits = RC6_6A_NBITS;
 189                         break;
 190                 default:
 191                         IR_dprintk(1, "RC6 unknown mode\n");
 192                         goto out;
 193                 }
 194                 goto again;
 195
 196         case STATE_BODY_BIT_START:
 197                 if (eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2)) {
 198                         /* Discard LSB's that won't fit in data->body */
 199                         if (data->count++ < CHAR_BIT * sizeof data->body) {
 200                                 data->body <<= 1;
 201                                 if (ev.pulse)
 202                                         data->body |= 1;
 203                         }
 204                         data->state = STATE_BODY_BIT_END;
 205                         return 0;
 206                 } else if (RC6_MODE_6A == rc6_mode(data) && !ev.pulse &&
 207                                 geq_margin(ev.duration, RC6_SUFFIX_SPACE, RC6_UNIT / 2)) {
 208                         data->state = STATE_FINISHED;
 209                         goto again;
 210                 }
 211                 break;
 212
 213         case STATE_BODY_BIT_END:
 214                 if (!is_transition(&ev, &dev->raw->prev_ev))
 215                         break;
 216
 217                 if (data->count == data->wanted_bits)
 218                         data->state = STATE_FINISHED;
 219                 else
 220                         data->state = STATE_BODY_BIT_START;
 221
 222                 decrease_duration(&ev, RC6_BIT_END);
 223                 goto again;
 224
 225         case STATE_FINISHED:
 226                 if (ev.pulse)
 227                         break;
 228
 229                 switch (rc6_mode(data)) {
 230                 case RC6_MODE_0:
 231                         scancode = data->body;
 232                         toggle = data->toggle;
 233                         protocol = RC_PROTO_RC6_0;
 234                         IR_dprintk(1, "RC6(0) scancode 0x%04x (toggle: %u)\n",
 235                                    scancode, toggle);
 236                         break;
 237
 238                 case RC6_MODE_6A:
 239                         if (data->count > CHAR_BIT * sizeof data->body) {
 240                                 IR_dprintk(1, "RC6 too many (%u) data bits\n",
 241                                         data->count);
 242                                 goto out;
 243                         }
 244
 245                         scancode = data->body;
 246                         switch (data->count) {
 247                         case 20:
 248                                 protocol = RC_PROTO_RC6_6A_20;
 249                                 toggle = 0;
 250                                 break;
 251                         case 24:
 252                                 protocol = RC_PROTO_RC6_6A_24;
 253                                 toggle = 0;
 254                                 break;
 255                         case 32:
 256                                 switch (scancode & RC6_6A_LCC_MASK) {
 257                                 case RC6_6A_MCE_CC:
 258                                 case RC6_6A_KATHREIN_CC:
 259                                         protocol = RC_PROTO_RC6_MCE;
 260                                         toggle = !!(scancode & RC6_6A_MCE_TOGGLE_MASK);
 261                                         scancode &= ~RC6_6A_MCE_TOGGLE_MASK;
 262                                         break;
 263                                 default:
 264                                         protocol = RC_PROTO_RC6_6A_32;
 265                                         toggle = 0;
 266                                         break;
 267                                 }
 268                                 break;
 269                         default:
 270                                 IR_dprintk(1, "RC6(6A) unsupported length\n");
 271                                 goto out;
 272                         }
 273
 274                         IR_dprintk(1, "RC6(6A) proto 0x%04x, scancode 0x%08x (toggle: %u)\n",
 275                                    protocol, scancode, toggle);
 276                         break;
 277                 default:
 278                         IR_dprintk(1, "RC6 unknown mode\n");
 279                         goto out;
 280                 }
 281
 282                 rc_keydown(dev, protocol, scancode, toggle);
 283                 data->state = STATE_INACTIVE;
 284                 return 0;
 285         }
 286
 287 out:
 288         IR_dprintk(1, "RC6 decode failed at state %i (%uus %s)\n",
 289                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 290         data->state = STATE_INACTIVE;
 291         return -EINVAL;
 292 }
 293
 294 static const struct ir_raw_timings_manchester ir_rc6_timings[4] = {
 295         {
 296                 .leader                 = RC6_PREFIX_PULSE,
 297                 .pulse_space_start      = 0,
 298                 .clock                  = RC6_UNIT,
 299                 .invert                 = 1,
 300                 .trailer_space          = RC6_PREFIX_SPACE,
 301         },
 302         {
 303                 .clock                  = RC6_UNIT,
 304                 .invert                 = 1,
 305         },
 306         {
 307                 .clock                  = RC6_UNIT * 2,
 308                 .invert                 = 1,
 309         },
 310         {
 311                 .clock                  = RC6_UNIT,
 312                 .invert                 = 1,
 313                 .trailer_space          = RC6_SUFFIX_SPACE,
 314         },
 315 };
 316
 317 /**
 318  * ir_rc6_encode() - Encode a scancode as a stream of raw events
 319  *
 320  * @protocol:   protocol to encode
 321  * @scancode:   scancode to encode
 322  * @events:     array of raw ir events to write into
 323  * @max:        maximum size of @events
 324  *
 325  * Returns:     The number of events written.
 326  *              -ENOBUFS if there isn't enough space in the array to fit the
 327  *              encoding. In this case all @max events will have been written.
 328  *              -EINVAL if the scancode is ambiguous or invalid.
 329  */
 330 static int ir_rc6_encode(enum rc_proto protocol, u32 scancode,
 331                          struct ir_raw_event *events, unsigned int max)
 332 {
 333         int ret;
 334         struct ir_raw_event *e = events;
 335
 336         if (protocol == RC_PROTO_RC6_0) {
 337                 /* Modulate the preamble */
 338                 ret = ir_raw_gen_manchester(&e, max, &ir_rc6_timings[0], 0, 0);
 339                 if (ret < 0)
 340                         return ret;
 341
 342                 /* Modulate the header (Start Bit & Mode-0) */
 343                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 344                                             &ir_rc6_timings[1],
 345                                             RC6_HEADER_NBITS, (1 << 3));
 346                 if (ret < 0)
 347                         return ret;
 348
 349                 /* Modulate Trailer Bit */
 350                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 351                                             &ir_rc6_timings[2], 1, 0);
 352                 if (ret < 0)
 353                         return ret;
 354
 355                 /* Modulate rest of the data */
 356                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 357                                             &ir_rc6_timings[3], RC6_0_NBITS,
 358                                             scancode);
 359                 if (ret < 0)
 360                         return ret;
 361
 362         } else {
 363                 int bits;
 364
 365                 switch (protocol) {
 366                 case RC_PROTO_RC6_MCE:
 367                 case RC_PROTO_RC6_6A_32:
 368                         bits = 32;
 369                         break;
 370                 case RC_PROTO_RC6_6A_24:
 371                         bits = 24;
 372                         break;
 373                 case RC_PROTO_RC6_6A_20:
 374                         bits = 20;
 375                         break;
 376                 default:
 377                         return -EINVAL;
 378                 }
 379
 380                 /* Modulate the preamble */
 381                 ret = ir_raw_gen_manchester(&e, max, &ir_rc6_timings[0], 0, 0);
 382                 if (ret < 0)
 383                         return ret;
 384
 385                 /* Modulate the header (Start Bit & Header-version 6 */
 386                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 387                                             &ir_rc6_timings[1],
 388                                             RC6_HEADER_NBITS, (1 << 3 | 6));
 389                 if (ret < 0)
 390                         return ret;
 391
 392                 /* Modulate Trailer Bit */
 393                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 394                                             &ir_rc6_timings[2], 1, 0);
 395                 if (ret < 0)
 396                         return ret;
 397
 398                 /* Modulate rest of the data */
 399                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 400                                             &ir_rc6_timings[3],
 401                                             bits,
 402                                             scancode);
 403                 if (ret < 0)
 404                         return ret;
 405         }
 406
 407         return e - events;
 408 }
 409
 410 static struct ir_raw_handler rc6_handler = {
 411         .protocols      = RC_PROTO_BIT_RC6_0 | RC_PROTO_BIT_RC6_6A_20 |
 412                           RC_PROTO_BIT_RC6_6A_24 | RC_PROTO_BIT_RC6_6A_32 |
 413                           RC_PROTO_BIT_RC6_MCE,
 414         .decode         = ir_rc6_decode,
 415         .encode         = ir_rc6_encode,
 416 };
 417
 418 static int __init ir_rc6_decode_init(void)
 419 {
 420         ir_raw_handler_register(&rc6_handler);
 421
 422         printk(KERN_INFO "IR RC6 protocol handler initialized\n");
 423         return 0;
 424 }
 425
 426 static void __exit ir_rc6_decode_exit(void)
 427 {
 428         ir_raw_handler_unregister(&rc6_handler);
 429 }
 430
 431 module_init(ir_rc6_decode_init);
 432 module_exit(ir_rc6_decode_exit);
 433
 434 MODULE_LICENSE("GPL");
 435 MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
 436 MODULE_DESCRIPTION("RC6 IR protocol decoder");