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/* ir-rc5-decoder.c - handle RC5(x) IR Pulse/Space protocol
*
* Copyright (C) 2010 by Mauro Carvalho Chehab <mchehab@redhat.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation version 2 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
/*
* This code handles 14 bits RC5 protocols and 20 bits RC5x protocols.
* There are other variants that use a different number of bits.
* This is currently unsupported.
* It considers a carrier of 36 kHz, with a total of 14/20 bits, where
* the first two bits are start bits, and a third one is a filing bit
*/
#include "rc-core-priv.h"
#include <linux/module.h>
#define RC5_NBITS 14
#define RC5X_NBITS 20
#define CHECK_RC5X_NBITS 8
#define RC5_UNIT 888888 /* ns */
#define RC5_BIT_START (1 * RC5_UNIT)
#define RC5_BIT_END (1 * RC5_UNIT)
#define RC5X_SPACE (4 * RC5_UNIT)
enum rc5_state {
STATE_INACTIVE,
STATE_BIT_START,
STATE_BIT_END,
STATE_CHECK_RC5X,
STATE_FINISHED,
};
/**
* ir_rc5_decode() - Decode one RC-5 pulse or space
* @dev: the struct rc_dev descriptor of the device
* @ev: the struct ir_raw_event descriptor of the pulse/space
*
* This function returns -EINVAL if the pulse violates the state machine
*/
static int ir_rc5_decode(struct rc_dev *dev, struct ir_raw_event ev)
{
struct rc5_dec *data = &dev->raw->rc5;
u8 toggle;
u32 scancode;
if (!(dev->raw->enabled_protocols & RC_TYPE_RC5))
return 0;
if (!is_timing_event(ev)) {
if (ev.reset)
data->state = STATE_INACTIVE;
return 0;
}
if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
goto out;
again:
IR_dprintk(2, "RC5(x) decode started at state %i (%uus %s)\n",
data->state, TO_US(ev.duration), TO_STR(ev.pulse));
if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
return 0;
switch (data->state) {
case STATE_INACTIVE:
if (!ev.pulse)
break;
data->state = STATE_BIT_START;
data->count = 1;
/* We just need enough bits to get to STATE_CHECK_RC5X */
data->wanted_bits = RC5X_NBITS;
decrease_duration(&ev, RC5_BIT_START);
goto again;
case STATE_BIT_START:
if (!eq_margin(ev.duration, RC5_BIT_START, RC5_UNIT / 2))
break;
data->bits <<= 1;
if (!ev.pulse)
data->bits |= 1;
data->count++;
data->state = STATE_BIT_END;
return 0;
case STATE_BIT_END:
if (!is_transition(&ev, &dev->raw->prev_ev))
break;
if (data->count == data->wanted_bits)
data->state = STATE_FINISHED;
else if (data->count == CHECK_RC5X_NBITS)
data->state = STATE_CHECK_RC5X;
else
data->state = STATE_BIT_START;
decrease_duration(&ev, RC5_BIT_END);
goto again;
case STATE_CHECK_RC5X:
if (!ev.pulse && geq_margin(ev.duration, RC5X_SPACE, RC5_UNIT / 2)) {
/* RC5X */
data->wanted_bits = RC5X_NBITS;
decrease_duration(&ev, RC5X_SPACE);
} else {
/* RC5 */
data->wanted_bits = RC5_NBITS;
}
data->state = STATE_BIT_START;
goto again;
case STATE_FINISHED:
if (ev.pulse)
break;
if (data->wanted_bits == RC5X_NBITS) {
/* RC5X */
u8 xdata, command, system;
xdata = (data->bits & 0x0003F) >> 0;
command = (data->bits & 0x00FC0) >> 6;
system = (data->bits & 0x1F000) >> 12;
toggle = (data->bits & 0x20000) ? 1 : 0;
command += (data->bits & 0x01000) ? 0 : 0x40;
scancode = system << 16 | command << 8 | xdata;
IR_dprintk(1, "RC5X scancode 0x%06x (toggle: %u)\n",
scancode, toggle);
} else {
/* RC5 */
u8 command, system;
command = (data->bits & 0x0003F) >> 0;
system = (data->bits & 0x007C0) >> 6;
toggle = (data->bits & 0x00800) ? 1 : 0;
command += (data->bits & 0x01000) ? 0 : 0x40;
scancode = system << 8 | command;
IR_dprintk(1, "RC5 scancode 0x%04x (toggle: %u)\n",
scancode, toggle);
}
rc_keydown(dev, scancode, toggle);
data->state = STATE_INACTIVE;
return 0;
}
out:
IR_dprintk(1, "RC5(x) decode failed at state %i (%uus %s)\n",
data->state, TO_US(ev.duration), TO_STR(ev.pulse));
data->state = STATE_INACTIVE;
return -EINVAL;
}
static struct ir_raw_handler rc5_handler = {
.protocols = RC_TYPE_RC5,
.decode = ir_rc5_decode,
};
static int __init ir_rc5_decode_init(void)
{
ir_raw_handler_register(&rc5_handler);
printk(KERN_INFO "IR RC5(x) protocol handler initialized\n");
return 0;
}
static void __exit ir_rc5_decode_exit(void)
{
ir_raw_handler_unregister(&rc5_handler);
}
module_init(ir_rc5_decode_init);
module_exit(ir_rc5_decode_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
MODULE_DESCRIPTION("RC5(x) IR protocol decoder");
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