/* 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 (!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 &&
                        /* DENON variant, both chk bits 0 */
                            (data->bits & 0x3) != 0x0)
                                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");