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 <mchehab@redhat.com>
   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 (!(dev->enabled_protocols & RC_BIT_NEC))
  56                 return 0;
  57
  58         if (!is_timing_event(ev)) {
  59                 if (ev.reset)
  60                         data->state = STATE_INACTIVE;
  61                 return 0;
  62         }
  63
  64         IR_dprintk(2, "NEC decode started at state %d (%uus %s)\n",
  65                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
  66
  67         switch (data->state) {
  68
  69         case STATE_INACTIVE:
  70                 if (!ev.pulse)
  71                         break;
  72
  73                 if (eq_margin(ev.duration, NEC_HEADER_PULSE, NEC_UNIT * 2)) {
  74                         data->is_nec_x = false;
  75                         data->necx_repeat = false;
  76                 } else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2))
  77                         data->is_nec_x = true;
  78                 else
  79                         break;
  80
  81                 data->count = 0;
  82                 data->state = STATE_HEADER_SPACE;
  83                 return 0;
  84
  85         case STATE_HEADER_SPACE:
  86                 if (ev.pulse)
  87                         break;
  88
  89                 if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT)) {
  90                         data->state = STATE_BIT_PULSE;
  91                         return 0;
  92                 } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) {
  93                         if (!dev->keypressed) {
  94                                 IR_dprintk(1, "Discarding last key repeat: event after key up\n");
  95                         } else {
  96                                 rc_repeat(dev);
  97                                 IR_dprintk(1, "Repeat last key\n");
  98                                 data->state = STATE_TRAILER_PULSE;
  99                         }
 100                         return 0;
 101                 }
 102
 103                 break;
 104
 105         case STATE_BIT_PULSE:
 106                 if (!ev.pulse)
 107                         break;
 108
 109                 if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))
 110                         break;
 111
 112                 data->state = STATE_BIT_SPACE;
 113                 return 0;
 114
 115         case STATE_BIT_SPACE:
 116                 if (ev.pulse)
 117                         break;
 118
 119                 if (data->necx_repeat && data->count == NECX_REPEAT_BITS &&
 120                         geq_margin(ev.duration,
 121                         NEC_TRAILER_SPACE, NEC_UNIT / 2)) {
 122                                 IR_dprintk(1, "Repeat last key\n");
 123                                 rc_repeat(dev);
 124                                 data->state = STATE_INACTIVE;
 125                                 return 0;
 126
 127                 } else if (data->count > NECX_REPEAT_BITS)
 128                         data->necx_repeat = false;
 129
 130                 data->bits <<= 1;
 131                 if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))
 132                         data->bits |= 1;
 133                 else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
 134                         break;
 135                 data->count++;
 136
 137                 if (data->count == NEC_NBITS)
 138                         data->state = STATE_TRAILER_PULSE;
 139                 else
 140                         data->state = STATE_BIT_PULSE;
 141
 142                 return 0;
 143
 144         case STATE_TRAILER_PULSE:
 145                 if (!ev.pulse)
 146                         break;
 147
 148                 if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
 149                         break;
 150
 151                 data->state = STATE_TRAILER_SPACE;
 152                 return 0;
 153
 154         case STATE_TRAILER_SPACE:
 155                 if (ev.pulse)
 156                         break;
 157
 158                 if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
 159                         break;
 160
 161                 address     = bitrev8((data->bits >> 24) & 0xff);
 162                 not_address = bitrev8((data->bits >> 16) & 0xff);
 163                 command     = bitrev8((data->bits >>  8) & 0xff);
 164                 not_command = bitrev8((data->bits >>  0) & 0xff);
 165
 166                 if ((command ^ not_command) != 0xff) {
 167                         IR_dprintk(1, "NEC checksum error: received 0x%08x\n",
 168                                    data->bits);
 169                         send_32bits = true;
 170                 }
 171
 172                 if (send_32bits) {
 173                         /* NEC transport, but modified protocol, used by at
 174                          * least Apple and TiVo remotes */
 175                         scancode = data->bits;
 176                         IR_dprintk(1, "NEC (modified) scancode 0x%08x\n", scancode);
 177                 } else if ((address ^ not_address) != 0xff) {
 178                         /* Extended NEC */
 179                         scancode = address     << 16 |
 180                                    not_address <<  8 |
 181                                    command;
 182                         IR_dprintk(1, "NEC (Ext) scancode 0x%06x\n", scancode);
 183                 } else {
 184                         /* Normal NEC */
 185                         scancode = address << 8 | command;
 186                         IR_dprintk(1, "NEC scancode 0x%04x\n", scancode);
 187                 }
 188
 189                 if (data->is_nec_x)
 190                         data->necx_repeat = true;
 191
 192                 rc_keydown(dev, scancode, 0);
 193                 data->state = STATE_INACTIVE;
 194                 return 0;
 195         }
 196
 197         IR_dprintk(1, "NEC decode failed at count %d state %d (%uus %s)\n",
 198                    data->count, data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 199         data->state = STATE_INACTIVE;
 200         return -EINVAL;
 201 }
 202
 203 static struct ir_raw_handler nec_handler = {
 204         .protocols      = RC_BIT_NEC,
 205         .decode         = ir_nec_decode,
 206 };
 207
 208 static int __init ir_nec_decode_init(void)
 209 {
 210         ir_raw_handler_register(&nec_handler);
 211
 212         printk(KERN_INFO "IR NEC protocol handler initialized\n");
 213         return 0;
 214 }
 215
 216 static void __exit ir_nec_decode_exit(void)
 217 {
 218         ir_raw_handler_unregister(&nec_handler);
 219 }
 220
 221 module_init(ir_nec_decode_init);
 222 module_exit(ir_nec_decode_exit);
 223
 224 MODULE_LICENSE("GPL");
 225 MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
 226 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 227 MODULE_DESCRIPTION("NEC IR protocol decoder");