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 "rc-core-priv.h"
  17
  18 #define NEC_NBITS               32
  19 #define NEC_UNIT                562500  /* ns */
  20 #define NEC_HEADER_PULSE        (16 * NEC_UNIT)
  21 #define NECX_HEADER_PULSE       (8  * NEC_UNIT) /* Less common NEC variant */
  22 #define NEC_HEADER_SPACE        (8  * NEC_UNIT)
  23 #define NEC_REPEAT_SPACE        (4  * NEC_UNIT)
  24 #define NEC_BIT_PULSE           (1  * NEC_UNIT)
  25 #define NEC_BIT_0_SPACE         (1  * NEC_UNIT)
  26 #define NEC_BIT_1_SPACE         (3  * NEC_UNIT)
  27 #define NEC_TRAILER_PULSE       (1  * NEC_UNIT)
  28 #define NEC_TRAILER_SPACE       (10 * NEC_UNIT) /* even longer in reality */
  29 #define NECX_REPEAT_BITS        1
  30
  31 enum nec_state {
  32         STATE_INACTIVE,
  33         STATE_HEADER_SPACE,
  34         STATE_BIT_PULSE,
  35         STATE_BIT_SPACE,
  36         STATE_TRAILER_PULSE,
  37         STATE_TRAILER_SPACE,
  38 };
  39
  40 /**
  41  * ir_nec_decode() - Decode one NEC pulse or space
  42  * @dev:        the struct rc_dev descriptor of the device
  43  * @duration:   the struct ir_raw_event descriptor of the pulse/space
  44  *
  45  * This function returns -EINVAL if the pulse violates the state machine
  46  */
  47 static int ir_nec_decode(struct rc_dev *dev, struct ir_raw_event ev)
  48 {
  49         struct nec_dec *data = &dev->raw->nec;
  50         u32 scancode;
  51         u8 address, not_address, command, not_command;
  52         bool send_32bits = false;
  53
  54         if (!(dev->raw->enabled_protocols & RC_TYPE_NEC))
  55                 return 0;
  56
  57         if (!is_timing_event(ev)) {
  58                 if (ev.reset)
  59                         data->state = STATE_INACTIVE;
  60                 return 0;
  61         }
  62
  63         IR_dprintk(2, "NEC decode started at state %d (%uus %s)\n",
  64                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
  65
  66         switch (data->state) {
  67
  68         case STATE_INACTIVE:
  69                 if (!ev.pulse)
  70                         break;
  71
  72                 if (eq_margin(ev.duration, NEC_HEADER_PULSE, NEC_UNIT / 2)) {
  73                         data->is_nec_x = false;
  74                         data->necx_repeat = false;
  75                 } else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2))
  76                         data->is_nec_x = true;
  77                 else
  78                         break;
  79
  80                 data->count = 0;
  81                 data->state = STATE_HEADER_SPACE;
  82                 return 0;
  83
  84         case STATE_HEADER_SPACE:
  85                 if (ev.pulse)
  86                         break;
  87
  88                 if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT / 2)) {
  89                         data->state = STATE_BIT_PULSE;
  90                         return 0;
  91                 } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) {
  92                         if (!dev->keypressed) {
  93                                 IR_dprintk(1, "Discarding last key repeat: event after key up\n");
  94                         } else {
  95                                 rc_repeat(dev);
  96                                 IR_dprintk(1, "Repeat last key\n");
  97                                 data->state = STATE_TRAILER_PULSE;
  98                         }
  99                         return 0;
 100                 }
 101
 102                 break;
 103
 104         case STATE_BIT_PULSE:
 105                 if (!ev.pulse)
 106                         break;
 107
 108                 if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))
 109                         break;
 110
 111                 data->state = STATE_BIT_SPACE;
 112                 return 0;
 113
 114         case STATE_BIT_SPACE:
 115                 if (ev.pulse)
 116                         break;
 117
 118                 if (data->necx_repeat && data->count == NECX_REPEAT_BITS &&
 119                         geq_margin(ev.duration,
 120                         NEC_TRAILER_SPACE, NEC_UNIT / 2)) {
 121                                 IR_dprintk(1, "Repeat last key\n");
 122                                 rc_repeat(dev);
 123                                 data->state = STATE_INACTIVE;
 124                                 return 0;
 125
 126                 } else if (data->count > NECX_REPEAT_BITS)
 127                         data->necx_repeat = false;
 128
 129                 data->bits <<= 1;
 130                 if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))
 131                         data->bits |= 1;
 132                 else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
 133                         break;
 134                 data->count++;
 135
 136                 if (data->count == NEC_NBITS)
 137                         data->state = STATE_TRAILER_PULSE;
 138                 else
 139                         data->state = STATE_BIT_PULSE;
 140
 141                 return 0;
 142
 143         case STATE_TRAILER_PULSE:
 144                 if (!ev.pulse)
 145                         break;
 146
 147                 if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
 148                         break;
 149
 150                 data->state = STATE_TRAILER_SPACE;
 151                 return 0;
 152
 153         case STATE_TRAILER_SPACE:
 154                 if (ev.pulse)
 155                         break;
 156
 157                 if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
 158                         break;
 159
 160                 address     = bitrev8((data->bits >> 24) & 0xff);
 161                 not_address = bitrev8((data->bits >> 16) & 0xff);
 162                 command     = bitrev8((data->bits >>  8) & 0xff);
 163                 not_command = bitrev8((data->bits >>  0) & 0xff);
 164
 165                 if ((command ^ not_command) != 0xff) {
 166                         IR_dprintk(1, "NEC checksum error: received 0x%08x\n",
 167                                    data->bits);
 168                         send_32bits = true;
 169                 }
 170
 171                 if (send_32bits) {
 172                         /* NEC transport, but modified protocol, used by at
 173                          * least Apple and TiVo remotes */
 174                         scancode = data->bits;
 175                         IR_dprintk(1, "NEC (modified) scancode 0x%08x\n", scancode);
 176                 } else if ((address ^ not_address) != 0xff) {
 177                         /* Extended NEC */
 178                         scancode = address     << 16 |
 179                                    not_address <<  8 |
 180                                    command;
 181                         IR_dprintk(1, "NEC (Ext) scancode 0x%06x\n", scancode);
 182                 } else {
 183                         /* Normal NEC */
 184                         scancode = address << 8 | command;
 185                         IR_dprintk(1, "NEC scancode 0x%04x\n", scancode);
 186                 }
 187
 188                 if (data->is_nec_x)
 189                         data->necx_repeat = true;
 190
 191                 rc_keydown(dev, scancode, 0);
 192                 data->state = STATE_INACTIVE;
 193                 return 0;
 194         }
 195
 196         IR_dprintk(1, "NEC decode failed at state %d (%uus %s)\n",
 197                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 198         data->state = STATE_INACTIVE;
 199         return -EINVAL;
 200 }
 201
 202 static struct ir_raw_handler nec_handler = {
 203         .protocols      = RC_TYPE_NEC,
 204         .decode         = ir_nec_decode,
 205 };
 206
 207 static int __init ir_nec_decode_init(void)
 208 {
 209         ir_raw_handler_register(&nec_handler);
 210
 211         printk(KERN_INFO "IR NEC protocol handler initialized\n");
 212         return 0;
 213 }
 214
 215 static void __exit ir_nec_decode_exit(void)
 216 {
 217         ir_raw_handler_unregister(&nec_handler);
 218 }
 219
 220 module_init(ir_nec_decode_init);
 221 module_exit(ir_nec_decode_exit);
 222
 223 MODULE_LICENSE("GPL");
 224 MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
 225 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 226 MODULE_DESCRIPTION("NEC IR protocol decoder");