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

   1 /* ir-nec-decoder.c - handle NEC IR Pulse/Space protocol
   2  *
   3  * Copyright (C) 2010 by Mauro Carvalho Chehab
   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 <linux/bitrev.h>
  16 #include <linux/module.h>
  17 #include "rc-core-priv.h"
  18
  19 #define NEC_NBITS               32
  20 #define NEC_UNIT                562500  /* ns */
  21 #define NEC_HEADER_PULSE        (16 * NEC_UNIT)
  22 #define NECX_HEADER_PULSE       (8  * NEC_UNIT) /* Less common NEC variant */
  23 #define NEC_HEADER_SPACE        (8  * NEC_UNIT)
  24 #define NEC_REPEAT_SPACE        (4  * NEC_UNIT)
  25 #define NEC_BIT_PULSE           (1  * NEC_UNIT)
  26 #define NEC_BIT_0_SPACE         (1  * NEC_UNIT)
  27 #define NEC_BIT_1_SPACE         (3  * NEC_UNIT)
  28 #define NEC_TRAILER_PULSE       (1  * NEC_UNIT)
  29 #define NEC_TRAILER_SPACE       (10 * NEC_UNIT) /* even longer in reality */
  30 #define NECX_REPEAT_BITS        1
  31
  32 enum nec_state {
  33         STATE_INACTIVE,
  34         STATE_HEADER_SPACE,
  35         STATE_BIT_PULSE,
  36         STATE_BIT_SPACE,
  37         STATE_TRAILER_PULSE,
  38         STATE_TRAILER_SPACE,
  39 };
  40
  41 /**
  42  * ir_nec_decode() - Decode one NEC pulse or space
  43  * @dev:        the struct rc_dev descriptor of the device
  44  * @duration:   the struct ir_raw_event descriptor of the pulse/space
  45  *
  46  * This function returns -EINVAL if the pulse violates the state machine
  47  */
  48 static int ir_nec_decode(struct rc_dev *dev, struct ir_raw_event ev)
  49 {
  50         struct nec_dec *data = &dev->raw->nec;
  51         u32 scancode;
  52         enum rc_proto rc_proto;
  53         u8 address, not_address, command, not_command;
  54
  55         if (!is_timing_event(ev)) {
  56                 if (ev.reset)
  57                         data->state = STATE_INACTIVE;
  58                 return 0;
  59         }
  60
  61         IR_dprintk(2, "NEC decode started at state %d (%uus %s)\n",
  62                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
  63
  64         switch (data->state) {
  65
  66         case STATE_INACTIVE:
  67                 if (!ev.pulse)
  68                         break;
  69
  70                 if (eq_margin(ev.duration, NEC_HEADER_PULSE, NEC_UNIT * 2)) {
  71                         data->is_nec_x = false;
  72                         data->necx_repeat = false;
  73                 } else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2))
  74                         data->is_nec_x = true;
  75                 else
  76                         break;
  77
  78                 data->count = 0;
  79                 data->state = STATE_HEADER_SPACE;
  80                 return 0;
  81
  82         case STATE_HEADER_SPACE:
  83                 if (ev.pulse)
  84                         break;
  85
  86                 if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT)) {
  87                         data->state = STATE_BIT_PULSE;
  88                         return 0;
  89                 } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) {
  90                         data->state = STATE_TRAILER_PULSE;
  91                         return 0;
  92                 }
  93
  94                 break;
  95
  96         case STATE_BIT_PULSE:
  97                 if (!ev.pulse)
  98                         break;
  99
 100                 if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))
 101                         break;
 102
 103                 data->state = STATE_BIT_SPACE;
 104                 return 0;
 105
 106         case STATE_BIT_SPACE:
 107                 if (ev.pulse)
 108                         break;
 109
 110                 if (data->necx_repeat && data->count == NECX_REPEAT_BITS &&
 111                         geq_margin(ev.duration,
 112                         NEC_TRAILER_SPACE, NEC_UNIT / 2)) {
 113                                 IR_dprintk(1, "Repeat last key\n");
 114                                 rc_repeat(dev);
 115                                 data->state = STATE_INACTIVE;
 116                                 return 0;
 117
 118                 } else if (data->count > NECX_REPEAT_BITS)
 119                         data->necx_repeat = false;
 120
 121                 data->bits <<= 1;
 122                 if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))
 123                         data->bits |= 1;
 124                 else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
 125                         break;
 126                 data->count++;
 127
 128                 if (data->count == NEC_NBITS)
 129                         data->state = STATE_TRAILER_PULSE;
 130                 else
 131                         data->state = STATE_BIT_PULSE;
 132
 133                 return 0;
 134
 135         case STATE_TRAILER_PULSE:
 136                 if (!ev.pulse)
 137                         break;
 138
 139                 if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
 140                         break;
 141
 142                 data->state = STATE_TRAILER_SPACE;
 143                 return 0;
 144
 145         case STATE_TRAILER_SPACE:
 146                 if (ev.pulse)
 147                         break;
 148
 149                 if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
 150                         break;
 151
 152                 if (data->count == NEC_NBITS) {
 153                         address     = bitrev8((data->bits >> 24) & 0xff);
 154                         not_address = bitrev8((data->bits >> 16) & 0xff);
 155                         command     = bitrev8((data->bits >>  8) & 0xff);
 156                         not_command = bitrev8((data->bits >>  0) & 0xff);
 157
 158                         scancode = ir_nec_bytes_to_scancode(address,
 159                                                             not_address,
 160                                                             command,
 161                                                             not_command,
 162                                                             &rc_proto);
 163
 164                         if (data->is_nec_x)
 165                                 data->necx_repeat = true;
 166
 167                         rc_keydown(dev, rc_proto, scancode, 0);
 168                 } else {
 169                         rc_repeat(dev);
 170                 }
 171
 172                 data->state = STATE_INACTIVE;
 173                 return 0;
 174         }
 175
 176         IR_dprintk(1, "NEC decode failed at count %d state %d (%uus %s)\n",
 177                    data->count, data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 178         data->state = STATE_INACTIVE;
 179         return -EINVAL;
 180 }
 181
 182 /**
 183  * ir_nec_scancode_to_raw() - encode an NEC scancode ready for modulation.
 184  * @protocol:   specific protocol to use
 185  * @scancode:   a single NEC scancode.
 186  * @raw:        raw data to be modulated.
 187  */
 188 static u32 ir_nec_scancode_to_raw(enum rc_proto protocol, u32 scancode)
 189 {
 190         unsigned int addr, addr_inv, data, data_inv;
 191
 192         data = scancode & 0xff;
 193
 194         if (protocol == RC_PROTO_NEC32) {
 195                 /* 32-bit NEC (used by Apple and TiVo remotes) */
 196                 /* scan encoding: aaAAddDD */
 197                 addr_inv   = (scancode >> 24) & 0xff;
 198                 addr       = (scancode >> 16) & 0xff;
 199                 data_inv   = (scancode >>  8) & 0xff;
 200         } else if (protocol == RC_PROTO_NECX) {
 201                 /* Extended NEC */
 202                 /* scan encoding AAaaDD */
 203                 addr       = (scancode >> 16) & 0xff;
 204                 addr_inv   = (scancode >>  8) & 0xff;
 205                 data_inv   = data ^ 0xff;
 206         } else {
 207                 /* Normal NEC */
 208                 /* scan encoding: AADD */
 209                 addr       = (scancode >>  8) & 0xff;
 210                 addr_inv   = addr ^ 0xff;
 211                 data_inv   = data ^ 0xff;
 212         }
 213
 214         /* raw encoding: ddDDaaAA */
 215         return data_inv << 24 |
 216                data     << 16 |
 217                addr_inv <<  8 |
 218                addr;
 219 }
 220
 221 static const struct ir_raw_timings_pd ir_nec_timings = {
 222         .header_pulse   = NEC_HEADER_PULSE,
 223         .header_space   = NEC_HEADER_SPACE,
 224         .bit_pulse      = NEC_BIT_PULSE,
 225         .bit_space[0]   = NEC_BIT_0_SPACE,
 226         .bit_space[1]   = NEC_BIT_1_SPACE,
 227         .trailer_pulse  = NEC_TRAILER_PULSE,
 228         .trailer_space  = NEC_TRAILER_SPACE,
 229         .msb_first      = 0,
 230 };
 231
 232 /**
 233  * ir_nec_encode() - Encode a scancode as a stream of raw events
 234  *
 235  * @protocol:   protocol to encode
 236  * @scancode:   scancode to encode
 237  * @events:     array of raw ir events to write into
 238  * @max:        maximum size of @events
 239  *
 240  * Returns:     The number of events written.
 241  *              -ENOBUFS if there isn't enough space in the array to fit the
 242  *              encoding. In this case all @max events will have been written.
 243  */
 244 static int ir_nec_encode(enum rc_proto protocol, u32 scancode,
 245                          struct ir_raw_event *events, unsigned int max)
 246 {
 247         struct ir_raw_event *e = events;
 248         int ret;
 249         u32 raw;
 250
 251         /* Convert a NEC scancode to raw NEC data */
 252         raw = ir_nec_scancode_to_raw(protocol, scancode);
 253
 254         /* Modulate the raw data using a pulse distance modulation */
 255         ret = ir_raw_gen_pd(&e, max, &ir_nec_timings, NEC_NBITS, raw);
 256         if (ret < 0)
 257                 return ret;
 258
 259         return e - events;
 260 }
 261
 262 static struct ir_raw_handler nec_handler = {
 263         .protocols      = RC_PROTO_BIT_NEC | RC_PROTO_BIT_NECX |
 264                                                         RC_PROTO_BIT_NEC32,
 265         .decode         = ir_nec_decode,
 266         .encode         = ir_nec_encode,
 267 };
 268
 269 static int __init ir_nec_decode_init(void)
 270 {
 271         ir_raw_handler_register(&nec_handler);
 272
 273         printk(KERN_INFO "IR NEC protocol handler initialized\n");
 274         return 0;
 275 }
 276
 277 static void __exit ir_nec_decode_exit(void)
 278 {
 279         ir_raw_handler_unregister(&nec_handler);
 280 }
 281
 282 module_init(ir_nec_decode_init);
 283 module_exit(ir_nec_decode_exit);
 284
 285 MODULE_LICENSE("GPL");
 286 MODULE_AUTHOR("Mauro Carvalho Chehab");
 287 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 288 MODULE_DESCRIPTION("NEC IR protocol decoder");