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/* ir-nec-decoder.c - handle NEC 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.
*/
#include <linux/bitrev.h>
#include "rc-core-priv.h"
#define NEC_NBITS 32
#define NEC_UNIT 562500 /* ns */
#define NEC_HEADER_PULSE (16 * NEC_UNIT)
#define NECX_HEADER_PULSE (8 * NEC_UNIT) /* Less common NEC variant */
#define NEC_HEADER_SPACE (8 * NEC_UNIT)
#define NEC_REPEAT_SPACE (4 * NEC_UNIT)
#define NEC_BIT_PULSE (1 * NEC_UNIT)
#define NEC_BIT_0_SPACE (1 * NEC_UNIT)
#define NEC_BIT_1_SPACE (3 * NEC_UNIT)
#define NEC_TRAILER_PULSE (1 * NEC_UNIT)
#define NEC_TRAILER_SPACE (10 * NEC_UNIT) /* even longer in reality */
#define NECX_REPEAT_BITS 1
enum nec_state {
STATE_INACTIVE,
STATE_HEADER_SPACE,
STATE_BIT_PULSE,
STATE_BIT_SPACE,
STATE_TRAILER_PULSE,
STATE_TRAILER_SPACE,
};
/**
* ir_nec_decode() - Decode one NEC 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_nec_decode(struct rc_dev *dev, struct ir_raw_event ev)
{
struct nec_dec *data = &dev->raw->nec;
u32 scancode;
u8 address, not_address, command, not_command;
if (!(dev->raw->enabled_protocols & IR_TYPE_NEC))
return 0;
if (!is_timing_event(ev)) {
if (ev.reset)
data->state = STATE_INACTIVE;
return 0;
}
IR_dprintk(2, "NEC 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, NEC_HEADER_PULSE, NEC_UNIT / 2)) {
data->is_nec_x = false;
data->necx_repeat = false;
} else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2))
data->is_nec_x = true;
else
break;
data->count = 0;
data->state = STATE_HEADER_SPACE;
return 0;
case STATE_HEADER_SPACE:
if (ev.pulse)
break;
if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT / 2)) {
data->state = STATE_BIT_PULSE;
return 0;
} else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) {
ir_repeat(dev);
IR_dprintk(1, "Repeat last key\n");
data->state = STATE_TRAILER_PULSE;
return 0;
}
break;
case STATE_BIT_PULSE:
if (!ev.pulse)
break;
if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))
break;
data->state = STATE_BIT_SPACE;
return 0;
case STATE_BIT_SPACE:
if (ev.pulse)
break;
if (data->necx_repeat && data->count == NECX_REPEAT_BITS &&
geq_margin(ev.duration,
NEC_TRAILER_SPACE, NEC_UNIT / 2)) {
IR_dprintk(1, "Repeat last key\n");
ir_repeat(dev);
data->state = STATE_INACTIVE;
return 0;
} else if (data->count > NECX_REPEAT_BITS)
data->necx_repeat = false;
data->bits <<= 1;
if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))
data->bits |= 1;
else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
break;
data->count++;
if (data->count == NEC_NBITS)
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, NEC_TRAILER_PULSE, NEC_UNIT / 2))
break;
data->state = STATE_TRAILER_SPACE;
return 0;
case STATE_TRAILER_SPACE:
if (ev.pulse)
break;
if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
break;
address = bitrev8((data->bits >> 24) & 0xff);
not_address = bitrev8((data->bits >> 16) & 0xff);
command = bitrev8((data->bits >> 8) & 0xff);
not_command = bitrev8((data->bits >> 0) & 0xff);
if ((command ^ not_command) != 0xff) {
IR_dprintk(1, "NEC checksum error: received 0x%08x\n",
data->bits);
break;
}
if ((address ^ not_address) != 0xff) {
/* Extended NEC */
scancode = address << 16 |
not_address << 8 |
command;
IR_dprintk(1, "NEC (Ext) scancode 0x%06x\n", scancode);
} else {
/* Normal NEC */
scancode = address << 8 | command;
IR_dprintk(1, "NEC scancode 0x%04x\n", scancode);
}
if (data->is_nec_x)
data->necx_repeat = true;
ir_keydown(dev, scancode, 0);
data->state = STATE_INACTIVE;
return 0;
}
IR_dprintk(1, "NEC decode failed at state %d (%uus %s)\n",
data->state, TO_US(ev.duration), TO_STR(ev.pulse));
data->state = STATE_INACTIVE;
return -EINVAL;
}
static struct ir_raw_handler nec_handler = {
.protocols = IR_TYPE_NEC,
.decode = ir_nec_decode,
};
static int __init ir_nec_decode_init(void)
{
ir_raw_handler_register(&nec_handler);
printk(KERN_INFO "IR NEC protocol handler initialized\n");
return 0;
}
static void __exit ir_nec_decode_exit(void)
{
ir_raw_handler_unregister(&nec_handler);
}
module_init(ir_nec_decode_init);
module_exit(ir_nec_decode_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
MODULE_DESCRIPTION("NEC IR protocol decoder");
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