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
  92         if (!rc_protocols_enabled(dev, RC_BIT_RC6_0 | RC_BIT_RC6_6A_20 |
  93                                   RC_BIT_RC6_6A_24 | RC_BIT_RC6_6A_32 |
  94                                   RC_BIT_RC6_MCE))
  95                 return 0;
  96
  97         if (!is_timing_event(ev)) {
  98                 if (ev.reset)
  99                         data->state = STATE_INACTIVE;
 100                 return 0;
 101         }
 102
 103         if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
 104                 goto out;
 105
 106 again:
 107         IR_dprintk(2, "RC6 decode started at state %i (%uus %s)\n",
 108                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 109
 110         if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
 111                 return 0;
 112
 113         switch (data->state) {
 114
 115         case STATE_INACTIVE:
 116                 if (!ev.pulse)
 117                         break;
 118
 119                 /* Note: larger margin on first pulse since each RC6_UNIT
 120                    is quite short and some hardware takes some time to
 121                    adjust to the signal */
 122                 if (!eq_margin(ev.duration, RC6_PREFIX_PULSE, RC6_UNIT))
 123                         break;
 124
 125                 data->state = STATE_PREFIX_SPACE;
 126                 data->count = 0;
 127                 return 0;
 128
 129         case STATE_PREFIX_SPACE:
 130                 if (ev.pulse)
 131                         break;
 132
 133                 if (!eq_margin(ev.duration, RC6_PREFIX_SPACE, RC6_UNIT / 2))
 134                         break;
 135
 136                 data->state = STATE_HEADER_BIT_START;
 137                 data->header = 0;
 138                 return 0;
 139
 140         case STATE_HEADER_BIT_START:
 141                 if (!eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2))
 142                         break;
 143
 144                 data->header <<= 1;
 145                 if (ev.pulse)
 146                         data->header |= 1;
 147                 data->count++;
 148                 data->state = STATE_HEADER_BIT_END;
 149                 return 0;
 150
 151         case STATE_HEADER_BIT_END:
 152                 if (!is_transition(&ev, &dev->raw->prev_ev))
 153                         break;
 154
 155                 if (data->count == RC6_HEADER_NBITS)
 156                         data->state = STATE_TOGGLE_START;
 157                 else
 158                         data->state = STATE_HEADER_BIT_START;
 159
 160                 decrease_duration(&ev, RC6_BIT_END);
 161                 goto again;
 162
 163         case STATE_TOGGLE_START:
 164                 if (!eq_margin(ev.duration, RC6_TOGGLE_START, RC6_UNIT / 2))
 165                         break;
 166
 167                 data->toggle = ev.pulse;
 168                 data->state = STATE_TOGGLE_END;
 169                 return 0;
 170
 171         case STATE_TOGGLE_END:
 172                 if (!is_transition(&ev, &dev->raw->prev_ev) ||
 173                     !geq_margin(ev.duration, RC6_TOGGLE_END, RC6_UNIT / 2))
 174                         break;
 175
 176                 if (!(data->header & RC6_STARTBIT_MASK)) {
 177                         IR_dprintk(1, "RC6 invalid start bit\n");
 178                         break;
 179                 }
 180
 181                 data->state = STATE_BODY_BIT_START;
 182                 decrease_duration(&ev, RC6_TOGGLE_END);
 183                 data->count = 0;
 184                 data->body = 0;
 185
 186                 switch (rc6_mode(data)) {
 187                 case RC6_MODE_0:
 188                         data->wanted_bits = RC6_0_NBITS;
 189                         break;
 190                 case RC6_MODE_6A:
 191                         data->wanted_bits = RC6_6A_NBITS;
 192                         break;
 193                 default:
 194                         IR_dprintk(1, "RC6 unknown mode\n");
 195                         goto out;
 196                 }
 197                 goto again;
 198
 199         case STATE_BODY_BIT_START:
 200                 if (eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2)) {
 201                         /* Discard LSB's that won't fit in data->body */
 202                         if (data->count++ < CHAR_BIT * sizeof data->body) {
 203                                 data->body <<= 1;
 204                                 if (ev.pulse)
 205                                         data->body |= 1;
 206                         }
 207                         data->state = STATE_BODY_BIT_END;
 208                         return 0;
 209                 } else if (RC6_MODE_6A == rc6_mode(data) && !ev.pulse &&
 210                                 geq_margin(ev.duration, RC6_SUFFIX_SPACE, RC6_UNIT / 2)) {
 211                         data->state = STATE_FINISHED;
 212                         goto again;
 213                 }
 214                 break;
 215
 216         case STATE_BODY_BIT_END:
 217                 if (!is_transition(&ev, &dev->raw->prev_ev))
 218                         break;
 219
 220                 if (data->count == data->wanted_bits)
 221                         data->state = STATE_FINISHED;
 222                 else
 223                         data->state = STATE_BODY_BIT_START;
 224
 225                 decrease_duration(&ev, RC6_BIT_END);
 226                 goto again;
 227
 228         case STATE_FINISHED:
 229                 if (ev.pulse)
 230                         break;
 231
 232                 switch (rc6_mode(data)) {
 233                 case RC6_MODE_0:
 234                         scancode = data->body;
 235                         toggle = data->toggle;
 236                         IR_dprintk(1, "RC6(0) scancode 0x%04x (toggle: %u)\n",
 237                                    scancode, toggle);
 238                         break;
 239                 case RC6_MODE_6A:
 240                         if (data->count > CHAR_BIT * sizeof data->body) {
 241                                 IR_dprintk(1, "RC6 too many (%u) data bits\n",
 242                                         data->count);
 243                                 goto out;
 244                         }
 245
 246                         scancode = data->body;
 247                         if (data->count == RC6_6A_32_NBITS &&
 248                                         (scancode & RC6_6A_LCC_MASK) == RC6_6A_MCE_CC) {
 249                                 /* MCE RC */
 250                                 toggle = (scancode & RC6_6A_MCE_TOGGLE_MASK) ? 1 : 0;
 251                                 scancode &= ~RC6_6A_MCE_TOGGLE_MASK;
 252                         } else {
 253                                 toggle = 0;
 254                         }
 255                         IR_dprintk(1, "RC6(6A) scancode 0x%08x (toggle: %u)\n",
 256                                    scancode, toggle);
 257                         break;
 258                 default:
 259                         IR_dprintk(1, "RC6 unknown mode\n");
 260                         goto out;
 261                 }
 262
 263                 rc_keydown(dev, scancode, toggle);
 264                 data->state = STATE_INACTIVE;
 265                 return 0;
 266         }
 267
 268 out:
 269         IR_dprintk(1, "RC6 decode failed at state %i (%uus %s)\n",
 270                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 271         data->state = STATE_INACTIVE;
 272         return -EINVAL;
 273 }
 274
 275 static struct ir_raw_handler rc6_handler = {
 276         .protocols      = RC_BIT_RC6_0 | RC_BIT_RC6_6A_20 |
 277                           RC_BIT_RC6_6A_24 | RC_BIT_RC6_6A_32 |
 278                           RC_BIT_RC6_MCE,
 279         .decode         = ir_rc6_decode,
 280 };
 281
 282 static int __init ir_rc6_decode_init(void)
 283 {
 284         ir_raw_handler_register(&rc6_handler);
 285
 286         printk(KERN_INFO "IR RC6 protocol handler initialized\n");
 287         return 0;
 288 }
 289
 290 static void __exit ir_rc6_decode_exit(void)
 291 {
 292         ir_raw_handler_unregister(&rc6_handler);
 293 }
 294
 295 module_init(ir_rc6_decode_init);
 296 module_exit(ir_rc6_decode_exit);
 297
 298 MODULE_LICENSE("GPL");
 299 MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
 300 MODULE_DESCRIPTION("RC6 IR protocol decoder");