drivers/media/rc/ir-rc5-decoder.c

   1 /* ir-rc5-decoder.c - decoder for RC5(x) and StreamZap protocols
   2  *
   3  * Copyright (C) 2010 by Mauro Carvalho Chehab
   4  * Copyright (C) 2010 by Jarod Wilson <jarod@redhat.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation version 2 of the License.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  */
  15
  16 /*
  17  * This decoder handles the 14 bit RC5 protocol, 15 bit "StreamZap" protocol
  18  * and 20 bit RC5x protocol.
  19  */
  20
  21 #include "rc-core-priv.h"
  22 #include <linux/module.h>
  23
  24 #define RC5_NBITS               14
  25 #define RC5_SZ_NBITS            15
  26 #define RC5X_NBITS              20
  27 #define CHECK_RC5X_NBITS        8
  28 #define RC5_UNIT                888888 /* ns */
  29 #define RC5_BIT_START           (1 * RC5_UNIT)
  30 #define RC5_BIT_END             (1 * RC5_UNIT)
  31 #define RC5X_SPACE              (4 * RC5_UNIT)
  32 #define RC5_TRAILER             (10 * RC5_UNIT) /* In reality, approx 100 */
  33
  34 enum rc5_state {
  35         STATE_INACTIVE,
  36         STATE_BIT_START,
  37         STATE_BIT_END,
  38         STATE_CHECK_RC5X,
  39         STATE_FINISHED,
  40 };
  41
  42 /**
  43  * ir_rc5_decode() - Decode one RC-5 pulse or space
  44  * @dev:        the struct rc_dev descriptor of the device
  45  * @ev:         the struct ir_raw_event descriptor of the pulse/space
  46  *
  47  * This function returns -EINVAL if the pulse violates the state machine
  48  */
  49 static int ir_rc5_decode(struct rc_dev *dev, struct ir_raw_event ev)
  50 {
  51         struct rc5_dec *data = &dev->raw->rc5;
  52         u8 toggle;
  53         u32 scancode;
  54         enum rc_type protocol;
  55
  56         if (!(dev->enabled_protocols & (RC_BIT_RC5 | RC_BIT_RC5X | RC_BIT_RC5_SZ)))
  57                 return 0;
  58
  59         if (!is_timing_event(ev)) {
  60                 if (ev.reset)
  61                         data->state = STATE_INACTIVE;
  62                 return 0;
  63         }
  64
  65         if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
  66                 goto out;
  67
  68 again:
  69         IR_dprintk(2, "RC5(x/sz) decode started at state %i (%uus %s)\n",
  70                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
  71
  72         if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
  73                 return 0;
  74
  75         switch (data->state) {
  76
  77         case STATE_INACTIVE:
  78                 if (!ev.pulse)
  79                         break;
  80
  81                 data->state = STATE_BIT_START;
  82                 data->count = 1;
  83                 decrease_duration(&ev, RC5_BIT_START);
  84                 goto again;
  85
  86         case STATE_BIT_START:
  87                 if (!ev.pulse && geq_margin(ev.duration, RC5_TRAILER, RC5_UNIT / 2)) {
  88                         data->state = STATE_FINISHED;
  89                         goto again;
  90                 }
  91
  92                 if (!eq_margin(ev.duration, RC5_BIT_START, RC5_UNIT / 2))
  93                         break;
  94
  95                 data->bits <<= 1;
  96                 if (!ev.pulse)
  97                         data->bits |= 1;
  98                 data->count++;
  99                 data->state = STATE_BIT_END;
 100                 return 0;
 101
 102         case STATE_BIT_END:
 103                 if (!is_transition(&ev, &dev->raw->prev_ev))
 104                         break;
 105
 106                 if (data->count == CHECK_RC5X_NBITS)
 107                         data->state = STATE_CHECK_RC5X;
 108                 else
 109                         data->state = STATE_BIT_START;
 110
 111                 decrease_duration(&ev, RC5_BIT_END);
 112                 goto again;
 113
 114         case STATE_CHECK_RC5X:
 115                 if (!ev.pulse && geq_margin(ev.duration, RC5X_SPACE, RC5_UNIT / 2)) {
 116                         data->is_rc5x = true;
 117                         decrease_duration(&ev, RC5X_SPACE);
 118                 } else
 119                         data->is_rc5x = false;
 120                 data->state = STATE_BIT_START;
 121                 goto again;
 122
 123         case STATE_FINISHED:
 124                 if (ev.pulse)
 125                         break;
 126
 127                 if (data->is_rc5x && data->count == RC5X_NBITS) {
 128                         /* RC5X */
 129                         u8 xdata, command, system;
 130                         if (!(dev->enabled_protocols & RC_BIT_RC5X)) {
 131                                 data->state = STATE_INACTIVE;
 132                                 return 0;
 133                         }
 134                         xdata    = (data->bits & 0x0003F) >> 0;
 135                         command  = (data->bits & 0x00FC0) >> 6;
 136                         system   = (data->bits & 0x1F000) >> 12;
 137                         toggle   = (data->bits & 0x20000) ? 1 : 0;
 138                         command += (data->bits & 0x01000) ? 0 : 0x40;
 139                         scancode = system << 16 | command << 8 | xdata;
 140                         protocol = RC_TYPE_RC5X;
 141
 142                 } else if (!data->is_rc5x && data->count == RC5_NBITS) {
 143                         /* RC5 */
 144                         u8 command, system;
 145                         if (!(dev->enabled_protocols & RC_BIT_RC5)) {
 146                                 data->state = STATE_INACTIVE;
 147                                 return 0;
 148                         }
 149                         command  = (data->bits & 0x0003F) >> 0;
 150                         system   = (data->bits & 0x007C0) >> 6;
 151                         toggle   = (data->bits & 0x00800) ? 1 : 0;
 152                         command += (data->bits & 0x01000) ? 0 : 0x40;
 153                         scancode = system << 8 | command;
 154                         protocol = RC_TYPE_RC5;
 155
 156                 } else if (!data->is_rc5x && data->count == RC5_SZ_NBITS) {
 157                         /* RC5 StreamZap */
 158                         u8 command, system;
 159                         if (!(dev->enabled_protocols & RC_BIT_RC5_SZ)) {
 160                                 data->state = STATE_INACTIVE;
 161                                 return 0;
 162                         }
 163                         command  = (data->bits & 0x0003F) >> 0;
 164                         system   = (data->bits & 0x02FC0) >> 6;
 165                         toggle   = (data->bits & 0x01000) ? 1 : 0;
 166                         scancode = system << 6 | command;
 167                         protocol = RC_TYPE_RC5_SZ;
 168
 169                 } else
 170                         break;
 171
 172                 IR_dprintk(1, "RC5(x/sz) scancode 0x%06x (p: %u, t: %u)\n",
 173                            scancode, protocol, toggle);
 174
 175                 rc_keydown(dev, protocol, scancode, toggle);
 176                 data->state = STATE_INACTIVE;
 177                 return 0;
 178         }
 179
 180 out:
 181         IR_dprintk(1, "RC5(x/sz) decode failed at state %i count %d (%uus %s)\n",
 182                    data->state, data->count, TO_US(ev.duration), TO_STR(ev.pulse));
 183         data->state = STATE_INACTIVE;
 184         return -EINVAL;
 185 }
 186
 187 static struct ir_raw_timings_manchester ir_rc5_timings = {
 188         .leader                 = RC5_UNIT,
 189         .pulse_space_start      = 0,
 190         .clock                  = RC5_UNIT,
 191         .trailer_space          = RC5_UNIT * 10,
 192 };
 193
 194 static struct ir_raw_timings_manchester ir_rc5x_timings[2] = {
 195         {
 196                 .leader                 = RC5_UNIT,
 197                 .pulse_space_start      = 0,
 198                 .clock                  = RC5_UNIT,
 199                 .trailer_space          = RC5X_SPACE,
 200         },
 201         {
 202                 .clock                  = RC5_UNIT,
 203                 .trailer_space          = RC5_UNIT * 10,
 204         },
 205 };
 206
 207 static struct ir_raw_timings_manchester ir_rc5_sz_timings = {
 208         .leader                         = RC5_UNIT,
 209         .pulse_space_start              = 0,
 210         .clock                          = RC5_UNIT,
 211         .trailer_space                  = RC5_UNIT * 10,
 212 };
 213
 214 static int ir_rc5_validate_filter(const struct rc_scancode_filter *scancode,
 215                                   unsigned int important_bits)
 216 {
 217         /* all important bits of scancode should be set in mask */
 218         if (~scancode->mask & important_bits)
 219                 return -EINVAL;
 220         /* extra bits in mask should be zero in data */
 221         if (scancode->mask & scancode->data & ~important_bits)
 222                 return -EINVAL;
 223         return 0;
 224 }
 225
 226 /**
 227  * ir_rc5_encode() - Encode a scancode as a stream of raw events
 228  *
 229  * @protocols:  allowed protocols
 230  * @scancode:   scancode filter describing scancode (helps distinguish between
 231  *              protocol subtypes when scancode is ambiguous)
 232  * @events:     array of raw ir events to write into
 233  * @max:        maximum size of @events
 234  *
 235  * Returns:     The number of events written.
 236  *              -ENOBUFS if there isn't enough space in the array to fit the
 237  *              encoding. In this case all @max events will have been written.
 238  *              -EINVAL if the scancode is ambiguous or invalid.
 239  */
 240 static int ir_rc5_encode(u64 protocols,
 241                          const struct rc_scancode_filter *scancode,
 242                          struct ir_raw_event *events, unsigned int max)
 243 {
 244         int ret;
 245         struct ir_raw_event *e = events;
 246         unsigned int data, xdata, command, commandx, system;
 247
 248         /* Detect protocol and convert scancode to raw data */
 249         if (protocols & RC_BIT_RC5 &&
 250             !ir_rc5_validate_filter(scancode, 0x1f7f)) {
 251                 /* decode scancode */
 252                 command  = (scancode->data & 0x003f) >> 0;
 253                 commandx = (scancode->data & 0x0040) >> 6;
 254                 system   = (scancode->data & 0x1f00) >> 8;
 255                 /* encode data */
 256                 data = !commandx << 12 | system << 6 | command;
 257
 258                 /* Modulate the data */
 259                 ret = ir_raw_gen_manchester(&e, max, &ir_rc5_timings, RC5_NBITS,
 260                                             data);
 261                 if (ret < 0)
 262                         return ret;
 263         } else if (protocols & RC_BIT_RC5X &&
 264                    !ir_rc5_validate_filter(scancode, 0x1f7f3f)) {
 265                 /* decode scancode */
 266                 xdata    = (scancode->data & 0x00003f) >> 0;
 267                 command  = (scancode->data & 0x003f00) >> 8;
 268                 commandx = (scancode->data & 0x004000) >> 14;
 269                 system   = (scancode->data & 0x1f0000) >> 16;
 270                 /* commandx and system overlap, bits must match when encoded */
 271                 if (commandx == (system & 0x1))
 272                         return -EINVAL;
 273                 /* encode data */
 274                 data = 1 << 18 | system << 12 | command << 6 | xdata;
 275
 276                 /* Modulate the data */
 277                 ret = ir_raw_gen_manchester(&e, max, &ir_rc5x_timings[0],
 278                                         CHECK_RC5X_NBITS,
 279                                         data >> (RC5X_NBITS-CHECK_RC5X_NBITS));
 280                 if (ret < 0)
 281                         return ret;
 282                 ret = ir_raw_gen_manchester(&e, max - (e - events),
 283                                         &ir_rc5x_timings[1],
 284                                         RC5X_NBITS - CHECK_RC5X_NBITS,
 285                                         data);
 286                 if (ret < 0)
 287                         return ret;
 288         } else if (protocols & RC_BIT_RC5_SZ &&
 289                    !ir_rc5_validate_filter(scancode, 0x2fff)) {
 290                 /* RC5-SZ scancode is raw enough for Manchester as it is */
 291                 ret = ir_raw_gen_manchester(&e, max, &ir_rc5_sz_timings,
 292                                         RC5_SZ_NBITS, scancode->data & 0x2fff);
 293                 if (ret < 0)
 294                         return ret;
 295         } else {
 296                 return -EINVAL;
 297         }
 298
 299         return e - events;
 300 }
 301
 302 static struct ir_raw_handler rc5_handler = {
 303         .protocols      = RC_BIT_RC5 | RC_BIT_RC5X | RC_BIT_RC5_SZ,
 304         .decode         = ir_rc5_decode,
 305         .encode         = ir_rc5_encode,
 306 };
 307
 308 static int __init ir_rc5_decode_init(void)
 309 {
 310         ir_raw_handler_register(&rc5_handler);
 311
 312         printk(KERN_INFO "IR RC5(x/sz) protocol handler initialized\n");
 313         return 0;
 314 }
 315
 316 static void __exit ir_rc5_decode_exit(void)
 317 {
 318         ir_raw_handler_unregister(&rc5_handler);
 319 }
 320
 321 module_init(ir_rc5_decode_init);
 322 module_exit(ir_rc5_decode_exit);
 323
 324 MODULE_LICENSE("GPL");
 325 MODULE_AUTHOR("Mauro Carvalho Chehab and Jarod Wilson");
 326 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 327 MODULE_DESCRIPTION("RC5(x/sz) IR protocol decoder");