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// SPDX-License-Identifier: GPL-2.0+
// ir-imon-decoder.c - handle iMon protocol
//
// Copyright (C) 2018 by Sean Young <sean@mess.org>
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include "rc-core-priv.h"
#define IMON_UNIT 415662 /* ns */
#define IMON_BITS 30
#define IMON_CHKBITS (BIT(30) | BIT(25) | BIT(24) | BIT(22) | \
BIT(21) | BIT(20) | BIT(19) | BIT(18) | \
BIT(17) | BIT(16) | BIT(14) | BIT(13) | \
BIT(12) | BIT(11) | BIT(10) | BIT(9))
/*
* This protocol has 30 bits. The format is one IMON_UNIT header pulse,
* followed by 30 bits. Each bit is one IMON_UNIT check field, and then
* one IMON_UNIT field with the actual bit (1=space, 0=pulse).
* The check field is always space for some bits, for others it is pulse if
* both the preceding and current bit are zero, else space. IMON_CHKBITS
* defines which bits are of type check.
*
* There is no way to distinguish an incomplete message from one where
* the lower bits are all set, iow. the last pulse is for the lowest
* bit which is 0.
*/
enum imon_state {
STATE_INACTIVE,
STATE_BIT_CHK,
STATE_BIT_START,
STATE_FINISHED
};
/**
* ir_imon_decode() - Decode one iMON 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_imon_decode(struct rc_dev *dev, struct ir_raw_event ev)
{
struct imon_dec *data = &dev->raw->imon;
if (!is_timing_event(ev)) {
if (ev.reset)
data->state = STATE_INACTIVE;
return 0;
}
dev_dbg(&dev->dev,
"iMON decode started at state %d bitno %d (%uus %s)\n",
data->state, data->count, TO_US(ev.duration),
TO_STR(ev.pulse));
for (;;) {
if (!geq_margin(ev.duration, IMON_UNIT, IMON_UNIT / 2))
return 0;
decrease_duration(&ev, IMON_UNIT);
switch (data->state) {
case STATE_INACTIVE:
if (ev.pulse) {
data->state = STATE_BIT_CHK;
data->bits = 0;
data->count = IMON_BITS;
}
break;
case STATE_BIT_CHK:
if (IMON_CHKBITS & BIT(data->count))
data->last_chk = ev.pulse;
else if (ev.pulse)
goto err_out;
data->state = STATE_BIT_START;
break;
case STATE_BIT_START:
data->bits <<= 1;
if (!ev.pulse)
data->bits |= 1;
if (IMON_CHKBITS & BIT(data->count)) {
if (data->last_chk != !(data->bits & 3))
goto err_out;
}
if (!data->count--)
data->state = STATE_FINISHED;
else
data->state = STATE_BIT_CHK;
break;
case STATE_FINISHED:
if (ev.pulse)
goto err_out;
rc_keydown(dev, RC_PROTO_IMON, data->bits, 0);
data->state = STATE_INACTIVE;
break;
}
}
err_out:
dev_dbg(&dev->dev,
"iMON decode failed at state %d bitno %d (%uus %s)\n",
data->state, data->count, TO_US(ev.duration),
TO_STR(ev.pulse));
data->state = STATE_INACTIVE;
return -EINVAL;
}
/**
* ir_imon_encode() - Encode a scancode as a stream of raw events
*
* @protocol: protocol to encode
* @scancode: scancode to encode
* @events: array of raw ir events to write into
* @max: maximum size of @events
*
* Returns: The number of events written.
* -ENOBUFS if there isn't enough space in the array to fit the
* encoding. In this case all @max events will have been written.
*/
static int ir_imon_encode(enum rc_proto protocol, u32 scancode,
struct ir_raw_event *events, unsigned int max)
{
struct ir_raw_event *e = events;
int i, pulse;
if (!max--)
return -ENOBUFS;
init_ir_raw_event_duration(e, 1, IMON_UNIT);
for (i = IMON_BITS; i >= 0; i--) {
if (BIT(i) & IMON_CHKBITS)
pulse = !(scancode & (BIT(i) | BIT(i + 1)));
else
pulse = 0;
if (pulse == e->pulse) {
e->duration += IMON_UNIT;
} else {
if (!max--)
return -ENOBUFS;
init_ir_raw_event_duration(++e, pulse, IMON_UNIT);
}
pulse = !(scancode & BIT(i));
if (pulse == e->pulse) {
e->duration += IMON_UNIT;
} else {
if (!max--)
return -ENOBUFS;
init_ir_raw_event_duration(++e, pulse, IMON_UNIT);
}
}
if (e->pulse)
e++;
return e - events;
}
static struct ir_raw_handler imon_handler = {
.protocols = RC_PROTO_BIT_IMON,
.decode = ir_imon_decode,
.encode = ir_imon_encode,
.carrier = 38000,
};
static int __init ir_imon_decode_init(void)
{
ir_raw_handler_register(&imon_handler);
pr_info("IR iMON protocol handler initialized\n");
return 0;
}
static void __exit ir_imon_decode_exit(void)
{
ir_raw_handler_unregister(&imon_handler);
}
module_init(ir_imon_decode_init);
module_exit(ir_imon_decode_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Sean Young <sean@mess.org>");
MODULE_DESCRIPTION("iMON IR protocol decoder");
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