drivers/media/rc/ir-rc5-decoder.c

   1 /* ir-rc5-decoder.c - handle RC5(x) 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 /*
  16  * This code handles 14 bits RC5 protocols and 20 bits RC5x protocols.
  17  * There are other variants that use a different number of bits.
  18  * This is currently unsupported.
  19  * It considers a carrier of 36 kHz, with a total of 14/20 bits, where
  20  * the first two bits are start bits, and a third one is a filing bit
  21  */
  22
  23 #include "rc-core-priv.h"
  24
  25 #define RC5_NBITS               14
  26 #define RC5X_NBITS              20
  27 #define CHECK_RC5X_NBITS        8
  28 #define RC5_UNIT                888888 /* ns */
  29 #define RC5_BIT_START           (1 * RC5_UNIT)
  30 #define RC5_BIT_END             (1 * RC5_UNIT)
  31 #define RC5X_SPACE              (4 * RC5_UNIT)
  32
  33 enum rc5_state {
  34         STATE_INACTIVE,
  35         STATE_BIT_START,
  36         STATE_BIT_END,
  37         STATE_CHECK_RC5X,
  38         STATE_FINISHED,
  39 };
  40
  41 /**
  42  * ir_rc5_decode() - Decode one RC-5 pulse or space
  43  * @dev:        the struct rc_dev descriptor of the device
  44  * @ev:         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_rc5_decode(struct rc_dev *dev, struct ir_raw_event ev)
  49 {
  50         struct rc5_dec *data = &dev->raw->rc5;
  51         u8 toggle;
  52         u32 scancode;
  53
  54         if (!(dev->raw->enabled_protocols & RC_TYPE_RC5))
  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         if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
  64                 goto out;
  65
  66 again:
  67         IR_dprintk(2, "RC5(x) decode started at state %i (%uus %s)\n",
  68                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
  69
  70         if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
  71                 return 0;
  72
  73         switch (data->state) {
  74
  75         case STATE_INACTIVE:
  76                 if (!ev.pulse)
  77                         break;
  78
  79                 data->state = STATE_BIT_START;
  80                 data->count = 1;
  81                 /* We just need enough bits to get to STATE_CHECK_RC5X */
  82                 data->wanted_bits = RC5X_NBITS;
  83                 decrease_duration(&ev, RC5_BIT_START);
  84                 goto again;
  85
  86         case STATE_BIT_START:
  87                 if (!eq_margin(ev.duration, RC5_BIT_START, RC5_UNIT / 2))
  88                         break;
  89
  90                 data->bits <<= 1;
  91                 if (!ev.pulse)
  92                         data->bits |= 1;
  93                 data->count++;
  94                 data->state = STATE_BIT_END;
  95                 return 0;
  96
  97         case STATE_BIT_END:
  98                 if (!is_transition(&ev, &dev->raw->prev_ev))
  99                         break;
 100
 101                 if (data->count == data->wanted_bits)
 102                         data->state = STATE_FINISHED;
 103                 else if (data->count == CHECK_RC5X_NBITS)
 104                         data->state = STATE_CHECK_RC5X;
 105                 else
 106                         data->state = STATE_BIT_START;
 107
 108                 decrease_duration(&ev, RC5_BIT_END);
 109                 goto again;
 110
 111         case STATE_CHECK_RC5X:
 112                 if (!ev.pulse && geq_margin(ev.duration, RC5X_SPACE, RC5_UNIT / 2)) {
 113                         /* RC5X */
 114                         data->wanted_bits = RC5X_NBITS;
 115                         decrease_duration(&ev, RC5X_SPACE);
 116                 } else {
 117                         /* RC5 */
 118                         data->wanted_bits = RC5_NBITS;
 119                 }
 120                 data->state = STATE_BIT_START;
 121                 goto again;
 122
 123         case STATE_FINISHED:
 124                 if (ev.pulse)
 125                         break;
 126
 127                 if (data->wanted_bits == RC5X_NBITS) {
 128                         /* RC5X */
 129                         u8 xdata, command, system;
 130                         xdata    = (data->bits & 0x0003F) >> 0;
 131                         command  = (data->bits & 0x00FC0) >> 6;
 132                         system   = (data->bits & 0x1F000) >> 12;
 133                         toggle   = (data->bits & 0x20000) ? 1 : 0;
 134                         command += (data->bits & 0x01000) ? 0 : 0x40;
 135                         scancode = system << 16 | command << 8 | xdata;
 136
 137                         IR_dprintk(1, "RC5X scancode 0x%06x (toggle: %u)\n",
 138                                    scancode, toggle);
 139
 140                 } else {
 141                         /* RC5 */
 142                         u8 command, system;
 143                         command  = (data->bits & 0x0003F) >> 0;
 144                         system   = (data->bits & 0x007C0) >> 6;
 145                         toggle   = (data->bits & 0x00800) ? 1 : 0;
 146                         command += (data->bits & 0x01000) ? 0 : 0x40;
 147                         scancode = system << 8 | command;
 148
 149                         IR_dprintk(1, "RC5 scancode 0x%04x (toggle: %u)\n",
 150                                    scancode, toggle);
 151                 }
 152
 153                 rc_keydown(dev, scancode, toggle);
 154                 data->state = STATE_INACTIVE;
 155                 return 0;
 156         }
 157
 158 out:
 159         IR_dprintk(1, "RC5(x) decode failed at state %i (%uus %s)\n",
 160                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 161         data->state = STATE_INACTIVE;
 162         return -EINVAL;
 163 }
 164
 165 static struct ir_raw_handler rc5_handler = {
 166         .protocols      = RC_TYPE_RC5,
 167         .decode         = ir_rc5_decode,
 168 };
 169
 170 static int __init ir_rc5_decode_init(void)
 171 {
 172         ir_raw_handler_register(&rc5_handler);
 173
 174         printk(KERN_INFO "IR RC5(x) protocol handler initialized\n");
 175         return 0;
 176 }
 177
 178 static void __exit ir_rc5_decode_exit(void)
 179 {
 180         ir_raw_handler_unregister(&rc5_handler);
 181 }
 182
 183 module_init(ir_rc5_decode_init);
 184 module_exit(ir_rc5_decode_exit);
 185
 186 MODULE_LICENSE("GPL");
 187 MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
 188 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 189 MODULE_DESCRIPTION("RC5(x) IR protocol decoder");