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

   1 /* ir-rc5-sz-decoder.c - handle RC5 Streamzap IR Pulse/Space protocol
   2  *
   3  * Copyright (C) 2010 by Mauro Carvalho Chehab <mchehab@redhat.com>
   4  * Copyright (C) 2010 by Jarod Wilson <jarod@redhat.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation version 2 of the License.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  */
  15
  16 /*
  17  * This code handles the 15 bit RC5-ish protocol used by the Streamzap
  18  * PC Remote.
  19  * It considers a carrier of 36 kHz, with a total of 15 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_SZ_NBITS            15
  26 #define RC5_UNIT                888888 /* ns */
  27 #define RC5_BIT_START           (1 * RC5_UNIT)
  28 #define RC5_BIT_END             (1 * RC5_UNIT)
  29
  30 enum rc5_sz_state {
  31         STATE_INACTIVE,
  32         STATE_BIT_START,
  33         STATE_BIT_END,
  34         STATE_FINISHED,
  35 };
  36
  37 /**
  38  * ir_rc5_sz_decode() - Decode one RC-5 Streamzap pulse or space
  39  * @dev:        the struct rc_dev descriptor of the device
  40  * @ev:         the struct ir_raw_event descriptor of the pulse/space
  41  *
  42  * This function returns -EINVAL if the pulse violates the state machine
  43  */
  44 static int ir_rc5_sz_decode(struct rc_dev *dev, struct ir_raw_event ev)
  45 {
  46         struct rc5_sz_dec *data = &dev->raw->rc5_sz;
  47         u8 toggle, command, system;
  48         u32 scancode;
  49
  50         if (!(dev->raw->enabled_protocols & RC_TYPE_RC5_SZ))
  51                 return 0;
  52
  53         if (!is_timing_event(ev)) {
  54                 if (ev.reset)
  55                         data->state = STATE_INACTIVE;
  56                 return 0;
  57         }
  58
  59         if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
  60                 goto out;
  61
  62 again:
  63         IR_dprintk(2, "RC5-sz decode started at state %i (%uus %s)\n",
  64                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
  65
  66         if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
  67                 return 0;
  68
  69         switch (data->state) {
  70
  71         case STATE_INACTIVE:
  72                 if (!ev.pulse)
  73                         break;
  74
  75                 data->state = STATE_BIT_START;
  76                 data->count = 1;
  77                 data->wanted_bits = RC5_SZ_NBITS;
  78                 decrease_duration(&ev, RC5_BIT_START);
  79                 goto again;
  80
  81         case STATE_BIT_START:
  82                 if (!eq_margin(ev.duration, RC5_BIT_START, RC5_UNIT / 2))
  83                         break;
  84
  85                 data->bits <<= 1;
  86                 if (!ev.pulse)
  87                         data->bits |= 1;
  88                 data->count++;
  89                 data->state = STATE_BIT_END;
  90                 return 0;
  91
  92         case STATE_BIT_END:
  93                 if (!is_transition(&ev, &dev->raw->prev_ev))
  94                         break;
  95
  96                 if (data->count == data->wanted_bits)
  97                         data->state = STATE_FINISHED;
  98                 else
  99                         data->state = STATE_BIT_START;
 100
 101                 decrease_duration(&ev, RC5_BIT_END);
 102                 goto again;
 103
 104         case STATE_FINISHED:
 105                 if (ev.pulse)
 106                         break;
 107
 108                 /* RC5-sz */
 109                 command  = (data->bits & 0x0003F) >> 0;
 110                 system   = (data->bits & 0x02FC0) >> 6;
 111                 toggle   = (data->bits & 0x01000) ? 1 : 0;
 112                 scancode = system << 6 | command;
 113
 114                 IR_dprintk(1, "RC5-sz scancode 0x%04x (toggle: %u)\n",
 115                            scancode, toggle);
 116
 117                 rc_keydown(dev, scancode, toggle);
 118                 data->state = STATE_INACTIVE;
 119                 return 0;
 120         }
 121
 122 out:
 123         IR_dprintk(1, "RC5-sz decode failed at state %i (%uus %s)\n",
 124                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 125         data->state = STATE_INACTIVE;
 126         return -EINVAL;
 127 }
 128
 129 static struct ir_raw_handler rc5_sz_handler = {
 130         .protocols      = RC_TYPE_RC5_SZ,
 131         .decode         = ir_rc5_sz_decode,
 132 };
 133
 134 static int __init ir_rc5_sz_decode_init(void)
 135 {
 136         ir_raw_handler_register(&rc5_sz_handler);
 137
 138         printk(KERN_INFO "IR RC5 (streamzap) protocol handler initialized\n");
 139         return 0;
 140 }
 141
 142 static void __exit ir_rc5_sz_decode_exit(void)
 143 {
 144         ir_raw_handler_unregister(&rc5_sz_handler);
 145 }
 146
 147 module_init(ir_rc5_sz_decode_init);
 148 module_exit(ir_rc5_sz_decode_exit);
 149
 150 MODULE_LICENSE("GPL");
 151 MODULE_AUTHOR("Jarod Wilson <jarod@redhat.com>");
 152 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 153 MODULE_DESCRIPTION("RC5 (streamzap) IR protocol decoder");