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 (!(dev->raw->enabled_protocols & RC_TYPE_RC6))
  93                 return 0;
  94
  95         if (!is_timing_event(ev)) {
  96                 if (ev.reset)
  97                         data->state = STATE_INACTIVE;
  98                 return 0;
  99         }
 100
 101         if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
 102                 goto out;
 103
 104 again:
 105         IR_dprintk(2, "RC6 decode started at state %i (%uus %s)\n",
 106                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 107
 108         if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
 109                 return 0;
 110
 111         switch (data->state) {
 112
 113         case STATE_INACTIVE:
 114                 if (!ev.pulse)
 115                         break;
 116
 117                 /* Note: larger margin on first pulse since each RC6_UNIT
 118                    is quite short and some hardware takes some time to
 119                    adjust to the signal */
 120                 if (!eq_margin(ev.duration, RC6_PREFIX_PULSE, RC6_UNIT))
 121                         break;
 122
 123                 data->state = STATE_PREFIX_SPACE;
 124                 data->count = 0;
 125                 return 0;
 126
 127         case STATE_PREFIX_SPACE:
 128                 if (ev.pulse)
 129                         break;
 130
 131                 if (!eq_margin(ev.duration, RC6_PREFIX_SPACE, RC6_UNIT / 2))
 132                         break;
 133
 134                 data->state = STATE_HEADER_BIT_START;
 135                 data->header = 0;
 136                 return 0;
 137
 138         case STATE_HEADER_BIT_START:
 139                 if (!eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2))
 140                         break;
 141
 142                 data->header <<= 1;
 143                 if (ev.pulse)
 144                         data->header |= 1;
 145                 data->count++;
 146                 data->state = STATE_HEADER_BIT_END;
 147                 return 0;
 148
 149         case STATE_HEADER_BIT_END:
 150                 if (!is_transition(&ev, &dev->raw->prev_ev))
 151                         break;
 152
 153                 if (data->count == RC6_HEADER_NBITS)
 154                         data->state = STATE_TOGGLE_START;
 155                 else
 156                         data->state = STATE_HEADER_BIT_START;
 157
 158                 decrease_duration(&ev, RC6_BIT_END);
 159                 goto again;
 160
 161         case STATE_TOGGLE_START:
 162                 if (!eq_margin(ev.duration, RC6_TOGGLE_START, RC6_UNIT / 2))
 163                         break;
 164
 165                 data->toggle = ev.pulse;
 166                 data->state = STATE_TOGGLE_END;
 167                 return 0;
 168
 169         case STATE_TOGGLE_END:
 170                 if (!is_transition(&ev, &dev->raw->prev_ev) ||
 171                     !geq_margin(ev.duration, RC6_TOGGLE_END, RC6_UNIT / 2))
 172                         break;
 173
 174                 if (!(data->header & RC6_STARTBIT_MASK)) {
 175                         IR_dprintk(1, "RC6 invalid start bit\n");
 176                         break;
 177                 }
 178
 179                 data->state = STATE_BODY_BIT_START;
 180                 decrease_duration(&ev, RC6_TOGGLE_END);
 181                 data->count = 0;
 182                 data->body = 0;
 183
 184                 switch (rc6_mode(data)) {
 185                 case RC6_MODE_0:
 186                         data->wanted_bits = RC6_0_NBITS;
 187                         break;
 188                 case RC6_MODE_6A:
 189                         data->wanted_bits = RC6_6A_NBITS;
 190                         break;
 191                 default:
 192                         IR_dprintk(1, "RC6 unknown mode\n");
 193                         goto out;
 194                 }
 195                 goto again;
 196
 197         case STATE_BODY_BIT_START:
 198                 if (eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2)) {
 199                         /* Discard LSB's that won't fit in data->body */
 200                         if (data->count++ < CHAR_BIT * sizeof data->body) {
 201                                 data->body <<= 1;
 202                                 if (ev.pulse)
 203                                         data->body |= 1;
 204                         }
 205                         data->state = STATE_BODY_BIT_END;
 206                         return 0;
 207                 } else if (RC6_MODE_6A == rc6_mode(data) && !ev.pulse &&
 208                                 geq_margin(ev.duration, RC6_SUFFIX_SPACE, RC6_UNIT / 2)) {
 209                         data->state = STATE_FINISHED;
 210                         goto again;
 211                 }
 212                 break;
 213
 214         case STATE_BODY_BIT_END:
 215                 if (!is_transition(&ev, &dev->raw->prev_ev))
 216                         break;
 217
 218                 if (data->count == data->wanted_bits)
 219                         data->state = STATE_FINISHED;
 220                 else
 221                         data->state = STATE_BODY_BIT_START;
 222
 223                 decrease_duration(&ev, RC6_BIT_END);
 224                 goto again;
 225
 226         case STATE_FINISHED:
 227                 if (ev.pulse)
 228                         break;
 229
 230                 switch (rc6_mode(data)) {
 231                 case RC6_MODE_0:
 232                         scancode = data->body;
 233                         toggle = data->toggle;
 234                         IR_dprintk(1, "RC6(0) scancode 0x%04x (toggle: %u)\n",
 235                                    scancode, toggle);
 236                         break;
 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                         if (data->count == RC6_6A_32_NBITS &&
 246                                         (scancode & RC6_6A_LCC_MASK) == RC6_6A_MCE_CC) {
 247                                 /* MCE RC */
 248                                 toggle = (scancode & RC6_6A_MCE_TOGGLE_MASK) ? 1 : 0;
 249                                 scancode &= ~RC6_6A_MCE_TOGGLE_MASK;
 250                         } else {
 251                                 toggle = 0;
 252                         }
 253                         IR_dprintk(1, "RC6(6A) scancode 0x%08x (toggle: %u)\n",
 254                                    scancode, toggle);
 255                         break;
 256                 default:
 257                         IR_dprintk(1, "RC6 unknown mode\n");
 258                         goto out;
 259                 }
 260
 261                 rc_keydown(dev, scancode, toggle);
 262                 data->state = STATE_INACTIVE;
 263                 return 0;
 264         }
 265
 266 out:
 267         IR_dprintk(1, "RC6 decode failed at state %i (%uus %s)\n",
 268                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 269         data->state = STATE_INACTIVE;
 270         return -EINVAL;
 271 }
 272
 273 static struct ir_raw_handler rc6_handler = {
 274         .protocols      = RC_TYPE_RC6,
 275         .decode         = ir_rc6_decode,
 276 };
 277
 278 static int __init ir_rc6_decode_init(void)
 279 {
 280         ir_raw_handler_register(&rc6_handler);
 281
 282         printk(KERN_INFO "IR RC6 protocol handler initialized\n");
 283         return 0;
 284 }
 285
 286 static void __exit ir_rc6_decode_exit(void)
 287 {
 288         ir_raw_handler_unregister(&rc6_handler);
 289 }
 290
 291 module_init(ir_rc6_decode_init);
 292 module_exit(ir_rc6_decode_exit);
 293
 294 MODULE_LICENSE("GPL");
 295 MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
 296 MODULE_DESCRIPTION("RC6 IR protocol decoder");