linux/drivers/media/rc/ir-rc5-sz-decoder.c
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   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
  31enum 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 */
  45static 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->raw->enabled_protocols & RC_TYPE_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
  63again:
  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
 123out:
 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
 130static struct ir_raw_handler rc5_sz_handler = {
 131        .protocols      = RC_TYPE_RC5_SZ,
 132        .decode         = ir_rc5_sz_decode,
 133};
 134
 135static 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
 143static void __exit ir_rc5_sz_decode_exit(void)
 144{
 145        ir_raw_handler_unregister(&rc5_sz_handler);
 146}
 147
 148module_init(ir_rc5_sz_decode_init);
 149module_exit(ir_rc5_sz_decode_exit);
 150
 151MODULE_LICENSE("GPL");
 152MODULE_AUTHOR("Jarod Wilson <jarod@redhat.com>");
 153MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 154MODULE_DESCRIPTION("RC5 (streamzap) IR protocol decoder");
 155