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
  30 enum nec_state {
  31         STATE_INACTIVE,
  32         STATE_HEADER_SPACE,
  33         STATE_BIT_PULSE,
  34         STATE_BIT_SPACE,
  35         STATE_TRAILER_PULSE,
  36         STATE_TRAILER_SPACE,
  37 };
  38
  39 /**
  40  * ir_nec_decode() - Decode one NEC pulse or space
  41  * @input_dev:  the struct input_dev descriptor of the device
  42  * @duration:   the struct ir_raw_event descriptor of the pulse/space
  43  *
  44  * This function returns -EINVAL if the pulse violates the state machine
  45  */
  46 static int ir_nec_decode(struct input_dev *input_dev, struct ir_raw_event ev)
  47 {
  48         struct ir_input_dev *ir_dev = input_get_drvdata(input_dev);
  49         struct nec_dec *data = &ir_dev->raw->nec;
  50         u32 scancode;
  51         u8 address, not_address, command, not_command;
  52
  53         if (!(ir_dev->raw->enabled_protocols & IR_TYPE_NEC))
  54                 return 0;
  55
  56         if (IS_RESET(ev)) {
  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                     !eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2))
  72                         break;
  73
  74                 data->count = 0;
  75                 data->state = STATE_HEADER_SPACE;
  76                 return 0;
  77
  78         case STATE_HEADER_SPACE:
  79                 if (ev.pulse)
  80                         break;
  81
  82                 if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT / 2)) {
  83                         data->state = STATE_BIT_PULSE;
  84                         return 0;
  85                 } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) {
  86                         ir_repeat(input_dev);
  87                         IR_dprintk(1, "Repeat last key\n");
  88                         data->state = STATE_TRAILER_PULSE;
  89                         return 0;
  90                 }
  91
  92                 break;
  93
  94         case STATE_BIT_PULSE:
  95                 if (!ev.pulse)
  96                         break;
  97
  98                 if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))
  99                         break;
 100
 101                 data->state = STATE_BIT_SPACE;
 102                 return 0;
 103
 104         case STATE_BIT_SPACE:
 105                 if (ev.pulse)
 106                         break;
 107
 108                 data->bits <<= 1;
 109                 if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))
 110                         data->bits |= 1;
 111                 else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
 112                         break;
 113                 data->count++;
 114
 115                 if (data->count == NEC_NBITS)
 116                         data->state = STATE_TRAILER_PULSE;
 117                 else
 118                         data->state = STATE_BIT_PULSE;
 119
 120                 return 0;
 121
 122         case STATE_TRAILER_PULSE:
 123                 if (!ev.pulse)
 124                         break;
 125
 126                 if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
 127                         break;
 128
 129                 data->state = STATE_TRAILER_SPACE;
 130                 return 0;
 131
 132         case STATE_TRAILER_SPACE:
 133                 if (ev.pulse)
 134                         break;
 135
 136                 if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
 137                         break;
 138
 139                 address     = bitrev8((data->bits >> 24) & 0xff);
 140                 not_address = bitrev8((data->bits >> 16) & 0xff);
 141                 command     = bitrev8((data->bits >>  8) & 0xff);
 142                 not_command = bitrev8((data->bits >>  0) & 0xff);
 143
 144                 if ((command ^ not_command) != 0xff) {
 145                         IR_dprintk(1, "NEC checksum error: received 0x%08x\n",
 146                                    data->bits);
 147                         break;
 148                 }
 149
 150                 if ((address ^ not_address) != 0xff) {
 151                         /* Extended NEC */
 152                         scancode = address     << 16 |
 153                                    not_address <<  8 |
 154                                    command;
 155                         IR_dprintk(1, "NEC (Ext) scancode 0x%06x\n", scancode);
 156                 } else {
 157                         /* Normal NEC */
 158                         scancode = address << 8 | command;
 159                         IR_dprintk(1, "NEC scancode 0x%04x\n", scancode);
 160                 }
 161
 162                 ir_keydown(input_dev, scancode, 0);
 163                 data->state = STATE_INACTIVE;
 164                 return 0;
 165         }
 166
 167         IR_dprintk(1, "NEC decode failed at state %d (%uus %s)\n",
 168                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 169         data->state = STATE_INACTIVE;
 170         return -EINVAL;
 171 }
 172
 173 static struct ir_raw_handler nec_handler = {
 174         .protocols      = IR_TYPE_NEC,
 175         .decode         = ir_nec_decode,
 176 };
 177
 178 static int __init ir_nec_decode_init(void)
 179 {
 180         ir_raw_handler_register(&nec_handler);
 181
 182         printk(KERN_INFO "IR NEC protocol handler initialized\n");
 183         return 0;
 184 }
 185
 186 static void __exit ir_nec_decode_exit(void)
 187 {
 188         ir_raw_handler_unregister(&nec_handler);
 189 }
 190
 191 module_init(ir_nec_decode_init);
 192 module_exit(ir_nec_decode_exit);
 193
 194 MODULE_LICENSE("GPL");
 195 MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
 196 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 197 MODULE_DESCRIPTION("NEC IR protocol decoder");