/* ir-jvc-decoder.c - handle JVC IR Pulse/Space protocol
 *
 * Copyright (C) 2010 by David Härdeman <david@hardeman.nu>
 *
 * 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 JVC_NBITS               16              /* dev(8) + func(8) */
#define JVC_UNIT                525000          /* ns */
#define JVC_HEADER_PULSE        (16 * JVC_UNIT) /* lack of header -> repeat */
#define JVC_HEADER_SPACE        (8  * JVC_UNIT)
#define JVC_BIT_PULSE           (1  * JVC_UNIT)
#define JVC_BIT_0_SPACE         (1  * JVC_UNIT)
#define JVC_BIT_1_SPACE         (3  * JVC_UNIT)
#define JVC_TRAILER_PULSE       (1  * JVC_UNIT)
#define JVC_TRAILER_SPACE       (35 * JVC_UNIT)

enum jvc_state {
        STATE_INACTIVE,
        STATE_HEADER_SPACE,
        STATE_BIT_PULSE,
        STATE_BIT_SPACE,
        STATE_TRAILER_PULSE,
        STATE_TRAILER_SPACE,
        STATE_CHECK_REPEAT,
};

/**
 * ir_jvc_decode() - Decode one JVC 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_jvc_decode(struct rc_dev *dev, struct ir_raw_event ev)
{
        struct jvc_dec *data = &dev->raw->jvc;

        if (!(dev->raw->enabled_protocols & RC_TYPE_JVC))
                return 0;

        if (!is_timing_event(ev)) {
                if (ev.reset)
                        data->state = STATE_INACTIVE;
                return 0;
        }

        if (!geq_margin(ev.duration, JVC_UNIT, JVC_UNIT / 2))
                goto out;

        IR_dprintk(2, "JVC decode started at state %d (%uus %s)\n",
                   data->state, TO_US(ev.duration), TO_STR(ev.pulse));

again:
        switch (data->state) {

        case STATE_INACTIVE:
                if (!ev.pulse)
                        break;

                if (!eq_margin(ev.duration, JVC_HEADER_PULSE, JVC_UNIT / 2))
                        break;

                data->count = 0;
                data->first = true;
                data->toggle = !data->toggle;
                data->state = STATE_HEADER_SPACE;
                return 0;

        case STATE_HEADER_SPACE:
                if (ev.pulse)
                        break;

                if (!eq_margin(ev.duration, JVC_HEADER_SPACE, JVC_UNIT / 2))
                        break;

                data->state = STATE_BIT_PULSE;
                return 0;

        case STATE_BIT_PULSE:
                if (!ev.pulse)
                        break;

                if (!eq_margin(ev.duration, JVC_BIT_PULSE, JVC_UNIT / 2))
                        break;

                data->state = STATE_BIT_SPACE;
                return 0;

        case STATE_BIT_SPACE:
                if (ev.pulse)
                        break;

                data->bits <<= 1;
                if (eq_margin(ev.duration, JVC_BIT_1_SPACE, JVC_UNIT / 2)) {
                        data->bits |= 1;
                        decrease_duration(&ev, JVC_BIT_1_SPACE);
                } else if (eq_margin(ev.duration, JVC_BIT_0_SPACE, JVC_UNIT / 2))
                        decrease_duration(&ev, JVC_BIT_0_SPACE);
                else
                        break;
                data->count++;

                if (data->count == JVC_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, JVC_TRAILER_PULSE, JVC_UNIT / 2))
                        break;

                data->state = STATE_TRAILER_SPACE;
                return 0;

        case STATE_TRAILER_SPACE:
                if (ev.pulse)
                        break;

                if (!geq_margin(ev.duration, JVC_TRAILER_SPACE, JVC_UNIT / 2))
                        break;

                if (data->first) {
                        u32 scancode;
                        scancode = (bitrev8((data->bits >> 8) & 0xff) << 8) |
                                   (bitrev8((data->bits >> 0) & 0xff) << 0);
                        IR_dprintk(1, "JVC scancode 0x%04x\n", scancode);
                        rc_keydown(dev, scancode, data->toggle);
                        data->first = false;
                        data->old_bits = data->bits;
                } else if (data->bits == data->old_bits) {
                        IR_dprintk(1, "JVC repeat\n");
                        rc_repeat(dev);
                } else {
                        IR_dprintk(1, "JVC invalid repeat msg\n");
                        break;
                }

                data->count = 0;
                data->state = STATE_CHECK_REPEAT;
                return 0;

        case STATE_CHECK_REPEAT:
                if (!ev.pulse)
                        break;

                if (eq_margin(ev.duration, JVC_HEADER_PULSE, JVC_UNIT / 2))
                        data->state = STATE_INACTIVE;
  else
                        data->state = STATE_BIT_PULSE;
                goto again;
        }

out:
        IR_dprintk(1, "JVC 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 jvc_handler = {
        .protocols      = RC_TYPE_JVC,
        .decode         = ir_jvc_decode,
};

static int __init ir_jvc_decode_init(void)
{
        ir_raw_handler_register(&jvc_handler);

        printk(KERN_INFO "IR JVC protocol handler initialized\n");
        return 0;
}

static void __exit ir_jvc_decode_exit(void)
{
        ir_raw_handler_unregister(&jvc_handler);
}

module_init(ir_jvc_decode_init);
module_exit(ir_jvc_decode_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
MODULE_DESCRIPTION("JVC IR protocol decoder");