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_type 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         IR_dprintk(2, "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 (!is_transition(&ev, &dev->raw->prev_ev))
 149                         break;
 150
 151                 if (data->count == RC6_HEADER_NBITS)
 152                         data->state = STATE_TOGGLE_START;
 153                 else
 154                         data->state = STATE_HEADER_BIT_START;
 155
 156                 decrease_duration(&ev, RC6_BIT_END);
 157                 goto again;
 158
 159         case STATE_TOGGLE_START:
 160                 if (!eq_margin(ev.duration, RC6_TOGGLE_START, RC6_UNIT / 2))
 161                         break;
 162
 163                 data->toggle = ev.pulse;
 164                 data->state = STATE_TOGGLE_END;
 165                 return 0;
 166
 167         case STATE_TOGGLE_END:
 168                 if (!is_transition(&ev, &dev->raw->prev_ev) ||
 169                     !geq_margin(ev.duration, RC6_TOGGLE_END, RC6_UNIT / 2))
 170                         break;
 171
 172                 if (!(data->header & RC6_STARTBIT_MASK)) {
 173                         IR_dprintk(1, "RC6 invalid start bit\n");
 174                         break;
 175                 }
 176
 177                 data->state = STATE_BODY_BIT_START;
 178                 decrease_duration(&ev, RC6_TOGGLE_END);
 179                 data->count = 0;
 180                 data->body = 0;
 181
 182                 switch (rc6_mode(data)) {
 183                 case RC6_MODE_0:
 184                         data->wanted_bits = RC6_0_NBITS;
 185                         break;
 186                 case RC6_MODE_6A:
 187                         data->wanted_bits = RC6_6A_NBITS;
 188                         break;
 189                 default:
 190                         IR_dprintk(1, "RC6 unknown mode\n");
 191                         goto out;
 192                 }
 193                 goto again;
 194
 195         case STATE_BODY_BIT_START:
 196                 if (eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2)) {
 197                         /* Discard LSB's that won't fit in data->body */
 198                         if (data->count++ < CHAR_BIT * sizeof data->body) {
 199                                 data->body <<= 1;
 200                                 if (ev.pulse)
 201                                         data->body |= 1;
 202                         }
 203                         data->state = STATE_BODY_BIT_END;
 204                         return 0;
 205                 } else if (RC6_MODE_6A == rc6_mode(data) && !ev.pulse &&
 206                                 geq_margin(ev.duration, RC6_SUFFIX_SPACE, RC6_UNIT / 2)) {
 207                         data->state = STATE_FINISHED;
 208                         goto again;
 209                 }
 210                 break;
 211
 212         case STATE_BODY_BIT_END:
 213                 if (!is_transition(&ev, &dev->raw->prev_ev))
 214                         break;
 215
 216                 if (data->count == data->wanted_bits)
 217                         data->state = STATE_FINISHED;
 218                 else
 219                         data->state = STATE_BODY_BIT_START;
 220
 221                 decrease_duration(&ev, RC6_BIT_END);
 222                 goto again;
 223
 224         case STATE_FINISHED:
 225                 if (ev.pulse)
 226                         break;
 227
 228                 switch (rc6_mode(data)) {
 229                 case RC6_MODE_0:
 230                         scancode = data->body;
 231                         toggle = data->toggle;
 232                         protocol = RC_TYPE_RC6_0;
 233                         IR_dprintk(1, "RC6(0) scancode 0x%04x (toggle: %u)\n",
 234                                    scancode, toggle);
 235                         break;
 236
 237                 case RC6_MODE_6A:
 238                         if (data->count > CHAR_BIT * sizeof data->body) {
 239                                 IR_dprintk(1, "RC6 too many (%u) data bits\n",
 240                                         data->count);
 241                                 goto out;
 242                         }
 243
 244                         scancode = data->body;
 245                         switch (data->count) {
 246                         case 20:
 247                                 protocol = RC_TYPE_RC6_6A_20;
 248                                 toggle = 0;
 249                                 break;
 250                         case 24:
 251                                 protocol = RC_BIT_RC6_6A_24;
 252                                 toggle = 0;
 253                                 break;
 254                         case 32:
 255                                 if ((scancode & RC6_6A_LCC_MASK) == RC6_6A_MCE_CC) {
 256                                         protocol = RC_TYPE_RC6_MCE;
 257                                         toggle = !!(scancode & RC6_6A_MCE_TOGGLE_MASK);
 258                                         scancode &= ~RC6_6A_MCE_TOGGLE_MASK;
 259                                 } else {
 260                                         protocol = RC_BIT_RC6_6A_32;
 261                                         toggle = 0;
 262                                 }
 263                                 break;
 264                         default:
 265                                 IR_dprintk(1, "RC6(6A) unsupported length\n");
 266                                 goto out;
 267                         }
 268
 269                         IR_dprintk(1, "RC6(6A) proto 0x%04x, scancode 0x%08x (toggle: %u)\n",
 270                                    protocol, scancode, toggle);
 271                         break;
 272                 default:
 273                         IR_dprintk(1, "RC6 unknown mode\n");
 274                         goto out;
 275                 }
 276
 277                 rc_keydown(dev, protocol, scancode, toggle);
 278                 data->state = STATE_INACTIVE;
 279                 return 0;
 280         }
 281
 282 out:
 283         IR_dprintk(1, "RC6 decode failed at state %i (%uus %s)\n",
 284                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 285         data->state = STATE_INACTIVE;
 286         return -EINVAL;
 287 }
 288
 289 static struct ir_raw_handler rc6_handler = {
 290         .protocols      = RC_BIT_RC6_0 | RC_BIT_RC6_6A_20 |
 291                           RC_BIT_RC6_6A_24 | RC_BIT_RC6_6A_32 |
 292                           RC_BIT_RC6_MCE,
 293         .decode         = ir_rc6_decode,
 294 };
 295
 296 static int __init ir_rc6_decode_init(void)
 297 {
 298         ir_raw_handler_register(&rc6_handler);
 299
 300         printk(KERN_INFO "IR RC6 protocol handler initialized\n");
 301         return 0;
 302 }
 303
 304 static void __exit ir_rc6_decode_exit(void)
 305 {
 306         ir_raw_handler_unregister(&rc6_handler);
 307 }
 308
 309 module_init(ir_rc6_decode_init);
 310 module_exit(ir_rc6_decode_exit);
 311
 312 MODULE_LICENSE("GPL");
 313 MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
 314 MODULE_DESCRIPTION("RC6 IR protocol decoder");