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

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* ir-rc6-decoder.c - A decoder for the RC6 IR protocol
   3  *
   4  * Copyright (C) 2010 by David Härdeman <david@hardeman.nu>
   5  */
   6
   7 #include "rc-core-priv.h"
   8 #include <linux/module.h>
   9
  10 /*
  11  * This decoder currently supports:
  12  * RC6-0-16     (standard toggle bit in header)
  13  * RC6-6A-20    (no toggle bit)
  14  * RC6-6A-24    (no toggle bit)
  15  * RC6-6A-32    (MCE version with toggle bit in body)
  16  */
  17
  18 #define RC6_UNIT                444     /* microseconds */
  19 #define RC6_HEADER_NBITS        4       /* not including toggle bit */
  20 #define RC6_0_NBITS             16
  21 #define RC6_6A_32_NBITS         32
  22 #define RC6_6A_NBITS            128     /* Variable 8..128 */
  23 #define RC6_PREFIX_PULSE        (6 * RC6_UNIT)
  24 #define RC6_PREFIX_SPACE        (2 * RC6_UNIT)
  25 #define RC6_BIT_START           (1 * RC6_UNIT)
  26 #define RC6_BIT_END             (1 * RC6_UNIT)
  27 #define RC6_TOGGLE_START        (2 * RC6_UNIT)
  28 #define RC6_TOGGLE_END          (2 * RC6_UNIT)
  29 #define RC6_SUFFIX_SPACE        (6 * RC6_UNIT)
  30 #define RC6_MODE_MASK           0x07    /* for the header bits */
  31 #define RC6_STARTBIT_MASK       0x08    /* for the header bits */
  32 #define RC6_6A_MCE_TOGGLE_MASK  0x8000  /* for the body bits */
  33 #define RC6_6A_LCC_MASK         0xffff0000 /* RC6-6A-32 long customer code mask */
  34 #define RC6_6A_MCE_CC           0x800f0000 /* MCE customer code */
  35 #define RC6_6A_ZOTAC_CC         0x80340000 /* Zotac customer code */
  36 #define RC6_6A_KATHREIN_CC      0x80460000 /* Kathrein RCU-676 customer code */
  37 #ifndef CHAR_BIT
  38 #define CHAR_BIT 8      /* Normally in <limits.h> */
  39 #endif
  40
  41 enum rc6_mode {
  42         RC6_MODE_0,
  43         RC6_MODE_6A,
  44         RC6_MODE_UNKNOWN,
  45 };
  46
  47 enum rc6_state {
  48         STATE_INACTIVE,
  49         STATE_PREFIX_SPACE,
  50         STATE_HEADER_BIT_START,
  51         STATE_HEADER_BIT_END,
  52         STATE_TOGGLE_START,
  53         STATE_TOGGLE_END,
  54         STATE_BODY_BIT_START,
  55         STATE_BODY_BIT_END,
  56         STATE_FINISHED,
  57 };
  58
  59 static enum rc6_mode rc6_mode(struct rc6_dec *data)
  60 {
  61         switch (data->header & RC6_MODE_MASK) {
  62         case 0:
  63                 return RC6_MODE_0;
  64         case 6:
  65                 if (!data->toggle)
  66                         return RC6_MODE_6A;
  67                 fallthrough;
  68         default:
  69                 return RC6_MODE_UNKNOWN;
  70         }
  71 }
  72
  73 /**
  74  * ir_rc6_decode() - Decode one RC6 pulse or space
  75  * @dev:        the struct rc_dev descriptor of the device
  76  * @ev:         the struct ir_raw_event descriptor of the pulse/space
  77  *
  78  * This function returns -EINVAL if the pulse violates the state machine
  79  */
  80 static int ir_rc6_decode(struct rc_dev *dev, struct ir_raw_event ev)
  81 {
  82         struct rc6_dec *data = &dev->raw->rc6;
  83         u32 scancode;
  84         u8 toggle;
  85         enum rc_proto protocol;
  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         dev_dbg(&dev->dev, "RC6 decode started at state %i (%uus %s)\n",
  98                 data->state, 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                 data->header = 0;
 128                 return 0;
 129
 130         case STATE_HEADER_BIT_START:
 131                 if (!eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2))
 132                         break;
 133
 134                 data->header <<= 1;
 135                 if (ev.pulse)
 136                         data->header |= 1;
 137                 data->count++;
 138                 data->state = STATE_HEADER_BIT_END;
 139                 return 0;
 140
 141         case STATE_HEADER_BIT_END:
 142                 if (data->count == RC6_HEADER_NBITS)
 143                         data->state = STATE_TOGGLE_START;
 144                 else
 145                         data->state = STATE_HEADER_BIT_START;
 146
 147                 decrease_duration(&ev, RC6_BIT_END);
 148                 goto again;
 149
 150         case STATE_TOGGLE_START:
 151                 if (!eq_margin(ev.duration, RC6_TOGGLE_START, RC6_UNIT / 2))
 152                         break;
 153
 154                 data->toggle = ev.pulse;
 155                 data->state = STATE_TOGGLE_END;
 156                 return 0;
 157
 158         case STATE_TOGGLE_END:
 159                 if (!(data->header & RC6_STARTBIT_MASK)) {
 160                         dev_dbg(&dev->dev, "RC6 invalid start bit\n");
 161                         break;
 162                 }
 163
 164                 data->state = STATE_BODY_BIT_START;
 165                 decrease_duration(&ev, RC6_TOGGLE_END);
 166                 data->count = 0;
 167                 data->body = 0;
 168
 169                 switch (rc6_mode(data)) {
 170                 case RC6_MODE_0:
 171                         data->wanted_bits = RC6_0_NBITS;
 172                         break;
 173                 case RC6_MODE_6A:
 174                         data->wanted_bits = RC6_6A_NBITS;
 175                         break;
 176                 default:
 177                         dev_dbg(&dev->dev, "RC6 unknown mode\n");
 178                         goto out;
 179                 }
 180                 goto again;
 181
 182         case STATE_BODY_BIT_START:
 183                 if (eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2)) {
 184                         /* Discard LSB's that won't fit in data->body */
 185                         if (data->count++ < CHAR_BIT * sizeof data->body) {
 186                                 data->body <<= 1;
 187                                 if (ev.pulse)
 188                                         data->body |= 1;
 189                         }
 190                         data->state = STATE_BODY_BIT_END;
 191                         return 0;
 192                 } else if (RC6_MODE_6A == rc6_mode(data) && !ev.pulse &&
 193                                 geq_margin(ev.duration, RC6_SUFFIX_SPACE, RC6_UNIT / 2)) {
 194                         data->state = STATE_FINISHED;
 195                         goto again;
 196                 }
 197                 break;
 198
 199         case STATE_BODY_BIT_END:
 200                 if (data->count == data->wanted_bits)
 201                         data->state = STATE_FINISHED;
 202                 else
 203                         data->state = STATE_BODY_BIT_START;
 204
 205                 decrease_duration(&ev, RC6_BIT_END);
 206                 goto again;
 207
 208         case STATE_FINISHED:
 209                 if (ev.pulse)
 210                         break;
 211
 212                 switch (rc6_mode(data)) {
 213                 case RC6_MODE_0:
 214                         scancode = data->body;
 215                         toggle = data->toggle;
 216                         protocol = RC_PROTO_RC6_0;
 217                         dev_dbg(&dev->dev, "RC6(0) scancode 0x%04x (toggle: %u)\n",
 218                                 scancode, toggle);
 219                         break;
 220
 221                 case RC6_MODE_6A:
 222                         if (data->count > CHAR_BIT * sizeof data->body) {
 223                                 dev_dbg(&dev->dev, "RC6 too many (%u) data bits\n",
 224                                         data->count);
 225                                 goto out;
 226                         }
 227
 228                         scancode = data->body;
 229                         switch (data->count) {
 230                         case 20:
 231                                 protocol = RC_PROTO_RC6_6A_20;
 232                                 toggle = 0;
 233                                 break;
 234                         case 24:
 235                                 protocol = RC_PROTO_RC6_6A_24;
 236                                 toggle = 0;
 237                                 break;
 238                         case 32:
 239                                 switch (scancode & RC6_6A_LCC_MASK) {
 240                                 case RC6_6A_MCE_CC:
 241                                 case RC6_6A_KATHREIN_CC:
 242                                 case RC6_6A_ZOTAC_CC:
 243                                         protocol = RC_PROTO_RC6_MCE;
 244                                         toggle = !!(scancode & RC6_6A_MCE_TOGGLE_MASK);
 245                                         scancode &= ~RC6_6A_MCE_TOGGLE_MASK;
 246                                         break;
 247                                 default:
 248                                         protocol = RC_PROTO_RC6_6A_32;
 249                                         toggle = 0;
 250                                         break;
 251                                 }
 252                                 break;
 253                         default:
 254                                 dev_dbg(&dev->dev, "RC6(6A) unsupported length\n");
 255                                 goto out;
 256                         }
 257
 258                         dev_dbg(&dev->dev, "RC6(6A) proto 0x%04x, scancode 0x%08x (toggle: %u)\n",
 259                                 protocol, scancode, toggle);
 260                         break;
 261                 default:
 262                         dev_dbg(&dev->dev, "RC6 unknown mode\n");
 263                         goto out;
 264                 }
 265
 266                 rc_keydown(dev, protocol, scancode, toggle);
 267                 data->state = STATE_INACTIVE;
 268                 return 0;
 269         }
 270
 271 out:
 272         dev_dbg(&dev->dev, "RC6 decode failed at state %i (%uus %s)\n",
 273                 data->state, ev.duration, TO_STR(ev.pulse));
 274         data->state = STATE_INACTIVE;
 275         return -EINVAL;
 276 }
 277
 278 static const struct ir_raw_timings_manchester ir_rc6_timings[4] = {
 279         {
 280                 .leader_pulse           = RC6_PREFIX_PULSE,
 281                 .leader_space           = RC6_PREFIX_SPACE,
 282                 .clock                  = RC6_UNIT,
 283                 .invert                 = 1,
 284         },
 285         {
 286                 .clock                  = RC6_UNIT * 2,
 287                 .invert                 = 1,
 288         },
 289         {
 290                 .clock                  = RC6_UNIT,
 291                 .invert                 = 1,
 292                 .trailer_space          = RC6_SUFFIX_SPACE,
 293         },
 294 };
 295
 296 /**
 297  * ir_rc6_encode() - Encode a scancode as a stream of raw events
 298  *
 299  * @protocol:   protocol to encode
 300  * @scancode:   scancode to encode
 301  * @events:     array of raw ir events to write into
 302  * @max:        maximum size of @events
 303  *
 304  * Returns:     The number of events written.
 305  *              -ENOBUFS if there isn't enough space in the array to fit the
 306  *              encoding. In this case all @max events will have been written.
 307  *              -EINVAL if the scancode is ambiguous or invalid.
 308  */
 309 static int ir_rc6_encode(enum rc_proto protocol, u32 scancode,
 310                          struct ir_raw_event *events, unsigned int max)
 311 {
 312         int ret;
 313         struct ir_raw_event *e = events;
 314
 315         if (protocol == RC_PROTO_RC6_0) {
 316                 /* Modulate the header (Start Bit & Mode-0) */
 317                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 318                                             &ir_rc6_timings[0],
 319                                             RC6_HEADER_NBITS, (1 << 3));
 320                 if (ret < 0)
 321                         return ret;
 322
 323                 /* Modulate Trailer Bit */
 324                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 325                                             &ir_rc6_timings[1], 1, 0);
 326                 if (ret < 0)
 327                         return ret;
 328
 329                 /* Modulate rest of the data */
 330                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 331                                             &ir_rc6_timings[2], RC6_0_NBITS,
 332                                             scancode);
 333                 if (ret < 0)
 334                         return ret;
 335
 336         } else {
 337                 int bits;
 338
 339                 switch (protocol) {
 340                 case RC_PROTO_RC6_MCE:
 341                 case RC_PROTO_RC6_6A_32:
 342                         bits = 32;
 343                         break;
 344                 case RC_PROTO_RC6_6A_24:
 345                         bits = 24;
 346                         break;
 347                 case RC_PROTO_RC6_6A_20:
 348                         bits = 20;
 349                         break;
 350                 default:
 351                         return -EINVAL;
 352                 }
 353
 354                 /* Modulate the header (Start Bit & Header-version 6 */
 355                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 356                                             &ir_rc6_timings[0],
 357                                             RC6_HEADER_NBITS, (1 << 3 | 6));
 358                 if (ret < 0)
 359                         return ret;
 360
 361                 /* Modulate Trailer Bit */
 362                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 363                                             &ir_rc6_timings[1], 1, 0);
 364                 if (ret < 0)
 365                         return ret;
 366
 367                 /* Modulate rest of the data */
 368                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 369                                             &ir_rc6_timings[2],
 370                                             bits,
 371                                             scancode);
 372                 if (ret < 0)
 373                         return ret;
 374         }
 375
 376         return e - events;
 377 }
 378
 379 static struct ir_raw_handler rc6_handler = {
 380         .protocols      = RC_PROTO_BIT_RC6_0 | RC_PROTO_BIT_RC6_6A_20 |
 381                           RC_PROTO_BIT_RC6_6A_24 | RC_PROTO_BIT_RC6_6A_32 |
 382                           RC_PROTO_BIT_RC6_MCE,
 383         .decode         = ir_rc6_decode,
 384         .encode         = ir_rc6_encode,
 385         .carrier        = 36000,
 386         .min_timeout    = RC6_SUFFIX_SPACE,
 387 };
 388
 389 static int __init ir_rc6_decode_init(void)
 390 {
 391         ir_raw_handler_register(&rc6_handler);
 392
 393         printk(KERN_INFO "IR RC6 protocol handler initialized\n");
 394         return 0;
 395 }
 396
 397 static void __exit ir_rc6_decode_exit(void)
 398 {
 399         ir_raw_handler_unregister(&rc6_handler);
 400 }
 401
 402 module_init(ir_rc6_decode_init);
 403 module_exit(ir_rc6_decode_exit);
 404
 405 MODULE_LICENSE("GPL");
 406 MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
 407 MODULE_DESCRIPTION("RC6 IR protocol decoder");