ir-nec-decoder.c

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/* ir-nec-decoder.c - handle NEC IR Pulse/Space protocol
 *
 * Copyright (C) 2010 by Mauro Carvalho Chehab <[email protected]>
 *
 * 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 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,
};

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;
    bool send_32bits = false;

    if (!(dev->raw->enabled_protocols & RC_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)) {
            data->state = STATE_BIT_PULSE;
            return 0;
        } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) {
            if (!dev->keypressed) {
                IR_dprintk(1, "Discarding last key repeat: event after key up\n");
            } else {
                rc_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");
                rc_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);
            send_32bits = true;
        }

        if (send_32bits) {
            /* NEC transport, but modified protocol, used by at
             * least Apple and TiVo remotes */
            scancode = data->bits;
            IR_dprintk(1, "NEC (modified) scancode 0x%08x\n", scancode);
        } else 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;

        rc_keydown(dev, scancode, 0);
        data->state = STATE_INACTIVE;
        return 0;
    }

    IR_dprintk(1, "NEC 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 nec_handler = {
    .protocols  = RC_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 <[email protected]>");
MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
MODULE_DESCRIPTION("NEC IR protocol decoder");