ir-sharp-decoder.c
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/* ir-sharp-decoder.c - handle Sharp IR Pulse/Space protocol
*
* Copyright (C) 2013-2014 Imagination Technologies Ltd.
*
* Based on NEC decoder:
* Copyright (C) 2010 by Mauro Carvalho Chehab
*
* 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.
*/
#include <linux/bitrev.h>
#include <linux/module.h>
#include "rc-core-priv.h"
#define SHARP_NBITS 15
#define SHARP_UNIT 40000 /* ns */
#define SHARP_BIT_PULSE (8 * SHARP_UNIT) /* 320us */
#define SHARP_BIT_0_PERIOD (25 * SHARP_UNIT) /* 1ms (680us space) */
#define SHARP_BIT_1_PERIOD (50 * SHARP_UNIT) /* 2ms (1680ms space) */
#define SHARP_ECHO_SPACE (1000 * SHARP_UNIT) /* 40 ms */
#define SHARP_TRAILER_SPACE (125 * SHARP_UNIT) /* 5 ms (even longer) */
enum sharp_state {
STATE_INACTIVE,
STATE_BIT_PULSE,
STATE_BIT_SPACE,
STATE_TRAILER_PULSE,
STATE_ECHO_SPACE,
STATE_TRAILER_SPACE,
};
/**
* ir_sharp_decode() - Decode one Sharp pulse or space
* @dev: the struct rc_dev descriptor of the device
* @duration: the struct ir_raw_event descriptor of the pulse/space
*
* This function returns -EINVAL if the pulse violates the state machine
*/
static int ir_sharp_decode(struct rc_dev *dev, struct ir_raw_event ev)
{
struct sharp_dec *data = &dev->raw->sharp;
u32 msg, echo, address, command, scancode;
if (!(dev->enabled_protocols & RC_BIT_SHARP))
return 0;
if (!is_timing_event(ev)) {
if (ev.reset)
data->state = STATE_INACTIVE;
return 0;
}
IR_dprintk(2, "Sharp decode started at state %d (%uus %s)\n",
data->state, TO_US(ev.duration), TO_STR(ev.pulse));
switch (data->state) {
case STATE_INACTIVE:
if (!ev.pulse)
break;
if (!eq_margin(ev.duration, SHARP_BIT_PULSE,
SHARP_BIT_PULSE / 2))
break;
data->count = 0;
data->pulse_len = ev.duration;
data->state = STATE_BIT_SPACE;
return 0;
case STATE_BIT_PULSE:
if (!ev.pulse)
break;
if (!eq_margin(ev.duration, SHARP_BIT_PULSE,
SHARP_BIT_PULSE / 2))
break;
data->pulse_len = ev.duration;
data->state = STATE_BIT_SPACE;
return 0;
case STATE_BIT_SPACE:
if (ev.pulse)
break;
data->bits <<= 1;
if (eq_margin(data->pulse_len + ev.duration, SHARP_BIT_1_PERIOD,
SHARP_BIT_PULSE * 2))
data->bits |= 1;
else if (!eq_margin(data->pulse_len + ev.duration,
SHARP_BIT_0_PERIOD, SHARP_BIT_PULSE * 2))
break;
data->count++;
if (data->count == SHARP_NBITS ||
data->count == SHARP_NBITS * 2)
data->state = STATE_TRAILER_PULSE;
else
data->state = STATE_BIT_PULSE;
return 0;
case STATE_TRAILER_PULSE:
if (!ev.pulse)
break;
if (!eq_margin(ev.duration, SHARP_BIT_PULSE,
SHARP_BIT_PULSE / 2))
break;
if (data->count == SHARP_NBITS) {
/* exp,chk bits should be 1,0 */
if ((data->bits & 0x3) != 0x2)
break;
data->state = STATE_ECHO_SPACE;
} else {
data->state = STATE_TRAILER_SPACE;
}
return 0;
case STATE_ECHO_SPACE:
if (ev.pulse)
break;
if (!eq_margin(ev.duration, SHARP_ECHO_SPACE,
SHARP_ECHO_SPACE / 4))
break;
data->state = STATE_BIT_PULSE;
return 0;
case STATE_TRAILER_SPACE:
if (ev.pulse)
break;
if (!geq_margin(ev.duration, SHARP_TRAILER_SPACE,
SHARP_BIT_PULSE / 2))
break;
/* Validate - command, ext, chk should be inverted in 2nd */
msg = (data->bits >> 15) & 0x7fff;
echo = data->bits & 0x7fff;
if ((msg ^ echo) != 0x3ff) {
IR_dprintk(1,
"Sharp checksum error: received 0x%04x, 0x%04x\n",
msg, echo);
break;
}
address = bitrev8((msg >> 7) & 0xf8);
command = bitrev8((msg >> 2) & 0xff);
scancode = address << 8 | command;
IR_dprintk(1, "Sharp scancode 0x%04x\n", scancode);
rc_keydown(dev, RC_TYPE_SHARP, scancode, 0);
data->state = STATE_INACTIVE;
return 0;
}
IR_dprintk(1, "Sharp decode failed at count %d state %d (%uus %s)\n",
data->count, data->state, TO_US(ev.duration),
TO_STR(ev.pulse));
data->state = STATE_INACTIVE;
return -EINVAL;
}
static struct ir_raw_handler sharp_handler = {
.protocols = RC_BIT_SHARP,
.decode = ir_sharp_decode,
};
static int __init ir_sharp_decode_init(void)
{
ir_raw_handler_register(&sharp_handler);
pr_info("IR Sharp protocol handler initialized\n");
return 0;
}
static void __exit ir_sharp_decode_exit(void)
{
ir_raw_handler_unregister(&sharp_handler);
}
module_init(ir_sharp_decode_init);
module_exit(ir_sharp_decode_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("James Hogan <james.hogan@imgtec.com>");
MODULE_DESCRIPTION("Sharp IR protocol decoder");