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 #include <linux/module.h>
  25
  26 #define RC5_SZ_NBITS            15
  27 #define RC5_UNIT                888888 /* ns */
  28 #define RC5_BIT_START           (1 * RC5_UNIT)
  29 #define RC5_BIT_END             (1 * RC5_UNIT)
  30
  31 enum rc5_sz_state {
  32         STATE_INACTIVE,
  33         STATE_BIT_START,
  34         STATE_BIT_END,
  35         STATE_FINISHED,
  36 };
  37
  38 /**
  39  * ir_rc5_sz_decode() - Decode one RC-5 Streamzap pulse or space
  40  * @dev:        the struct rc_dev descriptor of the device
  41  * @ev:         the struct ir_raw_event descriptor of the pulse/space
  42  *
  43  * This function returns -EINVAL if the pulse violates the state machine
  44  */
  45 static int ir_rc5_sz_decode(struct rc_dev *dev, struct ir_raw_event ev)
  46 {
  47         struct rc5_sz_dec *data = &dev->raw->rc5_sz;
  48         u8 toggle, command, system;
  49         u32 scancode;
  50
  51         if (!(dev->enabled_protocols & RC_BIT_RC5_SZ))
  52                 return 0;
  53
  54         if (!is_timing_event(ev)) {
  55                 if (ev.reset)
  56                         data->state = STATE_INACTIVE;
  57                 return 0;
  58         }
  59
  60         if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
  61                 goto out;
  62
  63 again:
  64         IR_dprintk(2, "RC5-sz decode started at state %i (%uus %s)\n",
  65                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
  66
  67         if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
  68                 return 0;
  69
  70         switch (data->state) {
  71
  72         case STATE_INACTIVE:
  73                 if (!ev.pulse)
  74                         break;
  75
  76                 data->state = STATE_BIT_START;
  77                 data->count = 1;
  78                 data->wanted_bits = RC5_SZ_NBITS;
  79                 decrease_duration(&ev, RC5_BIT_START);
  80                 goto again;
  81
  82         case STATE_BIT_START:
  83                 if (!eq_margin(ev.duration, RC5_BIT_START, RC5_UNIT / 2))
  84                         break;
  85
  86                 data->bits <<= 1;
  87                 if (!ev.pulse)
  88                         data->bits |= 1;
  89                 data->count++;
  90                 data->state = STATE_BIT_END;
  91                 return 0;
  92
  93         case STATE_BIT_END:
  94                 if (!is_transition(&ev, &dev->raw->prev_ev))
  95                         break;
  96
  97                 if (data->count == data->wanted_bits)
  98                         data->state = STATE_FINISHED;
  99                 else
 100                         data->state = STATE_BIT_START;
 101
 102                 decrease_duration(&ev, RC5_BIT_END);
 103                 goto again;
 104
 105         case STATE_FINISHED:
 106                 if (ev.pulse)
 107                         break;
 108
 109                 /* RC5-sz */
 110                 command  = (data->bits & 0x0003F) >> 0;
 111                 system   = (data->bits & 0x02FC0) >> 6;
 112                 toggle   = (data->bits & 0x01000) ? 1 : 0;
 113                 scancode = system << 6 | command;
 114
 115                 IR_dprintk(1, "RC5-sz scancode 0x%04x (toggle: %u)\n",
 116                            scancode, toggle);
 117
 118                 rc_keydown(dev, scancode, toggle);
 119                 data->state = STATE_INACTIVE;
 120                 return 0;
 121         }
 122
 123 out:
 124         IR_dprintk(1, "RC5-sz decode failed at state %i (%uus %s)\n",
 125                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 126         data->state = STATE_INACTIVE;
 127         return -EINVAL;
 128 }
 129
 130 static struct ir_raw_handler rc5_sz_handler = {
 131         .protocols      = RC_BIT_RC5_SZ,
 132         .decode         = ir_rc5_sz_decode,
 133 };
 134
 135 static int __init ir_rc5_sz_decode_init(void)
 136 {
 137         ir_raw_handler_register(&rc5_sz_handler);
 138
 139         printk(KERN_INFO "IR RC5 (streamzap) protocol handler initialized\n");
 140         return 0;
 141 }
 142
 143 static void __exit ir_rc5_sz_decode_exit(void)
 144 {
 145         ir_raw_handler_unregister(&rc5_sz_handler);
 146 }
 147
 148 module_init(ir_rc5_sz_decode_init);
 149 module_exit(ir_rc5_sz_decode_exit);
 150
 151 MODULE_LICENSE("GPL");
 152 MODULE_AUTHOR("Jarod Wilson <jarod@redhat.com>");
 153 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 154 MODULE_DESCRIPTION("RC5 (streamzap) IR protocol decoder");