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         u8 address, not_address, command, not_command;
  53         bool send_32bits = false;
  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                         if (!dev->keypressed) {
  91                                 IR_dprintk(1, "Discarding last key repeat: event after key up\n");
  92                         } else {
  93                                 rc_repeat(dev);
  94                                 IR_dprintk(1, "Repeat last key\n");
  95                                 data->state = STATE_TRAILER_PULSE;
  96                         }
  97                         return 0;
  98                 }
  99
 100                 break;
 101
 102         case STATE_BIT_PULSE:
 103                 if (!ev.pulse)
 104                         break;
 105
 106                 if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))
 107                         break;
 108
 109                 data->state = STATE_BIT_SPACE;
 110                 return 0;
 111
 112         case STATE_BIT_SPACE:
 113                 if (ev.pulse)
 114                         break;
 115
 116                 if (data->necx_repeat && data->count == NECX_REPEAT_BITS &&
 117                         geq_margin(ev.duration,
 118                         NEC_TRAILER_SPACE, NEC_UNIT / 2)) {
 119                                 IR_dprintk(1, "Repeat last key\n");
 120                                 rc_repeat(dev);
 121                                 data->state = STATE_INACTIVE;
 122                                 return 0;
 123
 124                 } else if (data->count > NECX_REPEAT_BITS)
 125                         data->necx_repeat = false;
 126
 127                 data->bits <<= 1;
 128                 if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))
 129                         data->bits |= 1;
 130                 else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
 131                         break;
 132                 data->count++;
 133
 134                 if (data->count == NEC_NBITS)
 135                         data->state = STATE_TRAILER_PULSE;
 136                 else
 137                         data->state = STATE_BIT_PULSE;
 138
 139                 return 0;
 140
 141         case STATE_TRAILER_PULSE:
 142                 if (!ev.pulse)
 143                         break;
 144
 145                 if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
 146                         break;
 147
 148                 data->state = STATE_TRAILER_SPACE;
 149                 return 0;
 150
 151         case STATE_TRAILER_SPACE:
 152                 if (ev.pulse)
 153                         break;
 154
 155                 if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
 156                         break;
 157
 158                 address     = bitrev8((data->bits >> 24) & 0xff);
 159                 not_address = bitrev8((data->bits >> 16) & 0xff);
 160                 command     = bitrev8((data->bits >>  8) & 0xff);
 161                 not_command = bitrev8((data->bits >>  0) & 0xff);
 162
 163                 if ((command ^ not_command) != 0xff) {
 164                         IR_dprintk(1, "NEC checksum error: received 0x%08x\n",
 165                                    data->bits);
 166                         send_32bits = true;
 167                 }
 168
 169                 if (send_32bits) {
 170                         /* NEC transport, but modified protocol, used by at
 171                          * least Apple and TiVo remotes */
 172                         scancode = data->bits;
 173                         IR_dprintk(1, "NEC (modified) scancode 0x%08x\n", scancode);
 174                 } else if ((address ^ not_address) != 0xff) {
 175                         /* Extended NEC */
 176                         scancode = address     << 16 |
 177                                    not_address <<  8 |
 178                                    command;
 179                         IR_dprintk(1, "NEC (Ext) scancode 0x%06x\n", scancode);
 180                 } else {
 181                         /* Normal NEC */
 182                         scancode = address << 8 | command;
 183                         IR_dprintk(1, "NEC scancode 0x%04x\n", scancode);
 184                 }
 185
 186                 if (data->is_nec_x)
 187                         data->necx_repeat = true;
 188
 189                 rc_keydown(dev, RC_TYPE_NEC, scancode, 0);
 190                 data->state = STATE_INACTIVE;
 191                 return 0;
 192         }
 193
 194         IR_dprintk(1, "NEC decode failed at count %d state %d (%uus %s)\n",
 195                    data->count, data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 196         data->state = STATE_INACTIVE;
 197         return -EINVAL;
 198 }
 199
 200 static struct ir_raw_handler nec_handler = {
 201         .protocols      = RC_BIT_NEC,
 202         .decode         = ir_nec_decode,
 203 };
 204
 205 static int __init ir_nec_decode_init(void)
 206 {
 207         ir_raw_handler_register(&nec_handler);
 208
 209         printk(KERN_INFO "IR NEC protocol handler initialized\n");
 210         return 0;
 211 }
 212
 213 static void __exit ir_nec_decode_exit(void)
 214 {
 215         ir_raw_handler_unregister(&nec_handler);
 216 }
 217
 218 module_init(ir_nec_decode_init);
 219 module_exit(ir_nec_decode_exit);
 220
 221 MODULE_LICENSE("GPL");
 222 MODULE_AUTHOR("Mauro Carvalho Chehab");
 223 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 224 MODULE_DESCRIPTION("NEC IR protocol decoder");