drivers/media/IR/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 "ir-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  * @input_dev:  the struct input_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 input_dev *input_dev, struct ir_raw_event ev)
  48 {
  49         struct ir_input_dev *ir_dev = input_get_drvdata(input_dev);
  50         struct nec_dec *data = &ir_dev->raw->nec;
  51         u32 scancode;
  52         u8 address, not_address, command, not_command;
  53
  54         if (!(ir_dev->raw->enabled_protocols & IR_TYPE_NEC))
  55                 return 0;
  56
  57         if (IS_RESET(ev)) {
  58                 data->state = STATE_INACTIVE;
  59                 return 0;
  60         }
  61
  62         IR_dprintk(2, "NEC decode started at state %d (%uus %s)\n",
  63                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
  64
  65         switch (data->state) {
  66
  67         case STATE_INACTIVE:
  68                 if (!ev.pulse)
  69                         break;
  70
  71                 if (eq_margin(ev.duration, NEC_HEADER_PULSE, NEC_UNIT / 2)) {
  72                         data->is_nec_x = false;
  73                         data->necx_repeat = false;
  74                 } else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2))
  75                         data->is_nec_x = true;
  76                 else
  77                         break;
  78
  79                 data->count = 0;
  80                 data->state = STATE_HEADER_SPACE;
  81                 return 0;
  82
  83         case STATE_HEADER_SPACE:
  84                 if (ev.pulse)
  85                         break;
  86
  87                 if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT / 2)) {
  88                         data->state = STATE_BIT_PULSE;
  89                         return 0;
  90                 } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) {
  91                         ir_repeat(input_dev);
  92                         IR_dprintk(1, "Repeat last key\n");
  93                         data->state = STATE_TRAILER_PULSE;
  94                         return 0;
  95                 }
  96
  97                 break;
  98
  99         case STATE_BIT_PULSE:
 100                 if (!ev.pulse)
 101                         break;
 102
 103                 if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))
 104                         break;
 105
 106                 data->state = STATE_BIT_SPACE;
 107                 return 0;
 108
 109         case STATE_BIT_SPACE:
 110                 if (ev.pulse)
 111                         break;
 112
 113                 if (data->necx_repeat && data->count == NECX_REPEAT_BITS &&
 114                         geq_margin(ev.duration,
 115                         NEC_TRAILER_SPACE, NEC_UNIT / 2)) {
 116                                 IR_dprintk(1, "Repeat last key\n");
 117                                 ir_repeat(input_dev);
 118                                 data->state = STATE_INACTIVE;
 119                                 return 0;
 120
 121                 } else if (data->count > NECX_REPEAT_BITS)
 122                         data->necx_repeat = false;
 123
 124                 data->bits <<= 1;
 125                 if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))
 126                         data->bits |= 1;
 127                 else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
 128                         break;
 129                 data->count++;
 130
 131                 if (data->count == NEC_NBITS)
 132                         data->state = STATE_TRAILER_PULSE;
 133                 else
 134                         data->state = STATE_BIT_PULSE;
 135
 136                 return 0;
 137
 138         case STATE_TRAILER_PULSE:
 139                 if (!ev.pulse)
 140                         break;
 141
 142                 if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
 143                         break;
 144
 145                 data->state = STATE_TRAILER_SPACE;
 146                 return 0;
 147
 148         case STATE_TRAILER_SPACE:
 149                 if (ev.pulse)
 150                         break;
 151
 152                 if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
 153                         break;
 154
 155                 address     = bitrev8((data->bits >> 24) & 0xff);
 156                 not_address = bitrev8((data->bits >> 16) & 0xff);
 157                 command     = bitrev8((data->bits >>  8) & 0xff);
 158                 not_command = bitrev8((data->bits >>  0) & 0xff);
 159
 160                 if ((command ^ not_command) != 0xff) {
 161                         IR_dprintk(1, "NEC checksum error: received 0x%08x\n",
 162                                    data->bits);
 163                         break;
 164                 }
 165
 166                 if ((address ^ not_address) != 0xff) {
 167                         /* Extended NEC */
 168                         scancode = address     << 16 |
 169                                    not_address <<  8 |
 170                                    command;
 171                         IR_dprintk(1, "NEC (Ext) scancode 0x%06x\n", scancode);
 172                 } else {
 173                         /* Normal NEC */
 174                         scancode = address << 8 | command;
 175                         IR_dprintk(1, "NEC scancode 0x%04x\n", scancode);
 176                 }
 177
 178                 if (data->is_nec_x)
 179                         data->necx_repeat = true;
 180
 181                 ir_keydown(input_dev, scancode, 0);
 182                 data->state = STATE_INACTIVE;
 183                 return 0;
 184         }
 185
 186         IR_dprintk(1, "NEC decode failed at state %d (%uus %s)\n",
 187                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 188         data->state = STATE_INACTIVE;
 189         return -EINVAL;
 190 }
 191
 192 static struct ir_raw_handler nec_handler = {
 193         .protocols      = IR_TYPE_NEC,
 194         .decode         = ir_nec_decode,
 195 };
 196
 197 static int __init ir_nec_decode_init(void)
 198 {
 199         ir_raw_handler_register(&nec_handler);
 200
 201         printk(KERN_INFO "IR NEC protocol handler initialized\n");
 202         return 0;
 203 }
 204
 205 static void __exit ir_nec_decode_exit(void)
 206 {
 207         ir_raw_handler_unregister(&nec_handler);
 208 }
 209
 210 module_init(ir_nec_decode_init);
 211 module_exit(ir_nec_decode_exit);
 212
 213 MODULE_LICENSE("GPL");
 214 MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
 215 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 216 MODULE_DESCRIPTION("NEC IR protocol decoder");