// SPDX-License-Identifier: GPL-2.0-only
/* ir-xmp-decoder.c - handle XMP IR Pulse/Space protocol
 *
 * Copyright (C) 2014 by Marcel Mol
 *
 * - Based on info from http://www.hifi-remote.com
 * - Ignore Toggle=9 frames
 * - Ignore XMP-1 XMP-2 difference, always store 16 bit OBC
 */

#include <linux/bitrev.h>
#include <linux/module.h>
#include "rc-core-priv.h"

#define XMP_UNIT                  136 /* us */
#define XMP_LEADER                210 /* us */
#define XMP_NIBBLE_PREFIX         760 /* us */
#define XMP_HALFFRAME_SPACE     13800 /* us */
/* should be 80ms but not all duration supliers can go that high */
#define XMP_TRAILER_SPACE       20000

enum xmp_state {
        STATE_INACTIVE,
        STATE_LEADER_PULSE,
        STATE_NIBBLE_SPACE,
};

/**
 * ir_xmp_decode() - Decode one XMP 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_xmp_decode(struct rc_dev *dev, struct ir_raw_event ev)
{
        struct xmp_dec *data = &dev->raw->xmp;

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

        dev_dbg(&dev->dev, "XMP decode started at state %d %d (%uus %s)\n",
                data->state, data->count, ev.duration, TO_STR(ev.pulse));

        switch (data->state) {

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

                if (eq_margin(ev.duration, XMP_LEADER, XMP_UNIT / 2)) {
                        data->count = 0;
                        data->state = STATE_NIBBLE_SPACE;
                }

                return 0;

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

                if (eq_margin(ev.duration, XMP_LEADER, XMP_UNIT / 2))
                        data->state = STATE_NIBBLE_SPACE;

                return 0;

        case STATE_NIBBLE_SPACE:
                if (ev.pulse)
                        break;

                if (geq_margin(ev.duration, XMP_TRAILER_SPACE, XMP_NIBBLE_PREFIX)) {
                        int divider, i;
                        u8 addr, subaddr, subaddr2, toggle, oem, obc1, obc2, sum1, sum2;
                        u32 *n;
                        u32 scancode;

                        if (data->count != 16) {
                                dev_dbg(&dev->dev, "received TRAILER period at index %d: %u\n",
                                        data->count, ev.duration);
                                data->state = STATE_INACTIVE;
                                return -EINVAL;
                        }

                        n = data->durations;
                        /*
                         * the 4th nibble should be 15 so base the divider on this
                         * to transform durations into nibbles. Subtract 2000 from
                         * the divider to compensate for fluctuations in the signal
                         */
                        divider = (n[3] - XMP_NIBBLE_PREFIX) / 15 - 2000;
                        if (divider < 50) {
                                dev_dbg(&dev->dev, "divider to small %d.\n",
                                        divider);
                                data->state = STATE_INACTIVE;
                                return -EINVAL;
                        }

                        /* convert to nibbles and do some sanity checks */
                        for (i = 0; i < 16; i++)
                                n[i] = (n[i] - XMP_NIBBLE_PREFIX) / divider;
                        sum1 = (15 + n[0] + n[1] + n[2] + n[3] +
                                n[4] + n[5] + n[6] + n[7]) % 16;
                        sum2 = (15 + n[8] + n[9] + n[10] + n[11] +
                                n[12] + n[13] + n[14] + n[15]) % 16;

                        if (sum1 != 15 || sum2 != 15) {
                                dev_dbg(&dev->dev, "checksum errors sum1=0x%X sum2=0x%X\n",
                                        sum1, sum2);
                                data->state = STATE_INACTIVE;
                                return -EINVAL;
                        }

                        subaddr  = n[0] << 4 | n[2];
                        subaddr2 = n[8] << 4 | n[11];
                        oem      = n[4] << 4 | n[5];
                        addr     = n[6] << 4 | n[7];
                        toggle   = n[10];
                        obc1 = n[12] << 4 | n[13];
                        obc2 = n[14] << 4 | n[15];
                        if (subaddr != subaddr2) {
                                dev_dbg(&dev->dev, "subaddress nibbles mismatch 0x%02X != 0x%02X\n",
                                        subaddr, subaddr2);
                                data->state = STATE_INACTIVE;
                                return -EINVAL;
                        }
                        if (oem != 0x44)
                                dev_dbg(&dev->dev, "Warning: OEM nibbles 0x%02X. Expected 0x44\n",
                                        oem);

                        scancode = addr << 24 | subaddr << 16 |
                                   obc1 << 8 | obc2;
                        dev_dbg(&dev->dev, "XMP scancode 0x%06x\n", scancode);

                        if (toggle == 0) {
                                rc_keydown(dev, RC_PROTO_XMP, scancode, 0);
                        } else {
                                rc_repeat(dev);
                                dev_dbg(&dev->dev, "Repeat last key\n");
                        }
                        data->state = STATE_INACTIVE;

                        return 0;

                } else if (geq_margin(ev.duration, XMP_HALFFRAME_SPACE, XMP_NIBBLE_PREFIX)) {
                        /* Expect 8 or 16 nibble pulses. 16 in case of 'final' frame */
                        if (data->count == 16) {
                                dev_dbg(&dev->dev, "received half frame pulse at index %d. Probably a final frame key-up event: %u\n",
                                        data->count, ev.duration);
                                /*
                                 * TODO: for now go back to half frame position
                                 *       so trailer can be found and key press
                                 *       can be handled.
                                 */
                                data->count = 8;
                        }

                        else if (data->count != 8)
                                dev_dbg(&dev->dev, "received half frame pulse at index %d: %u\n",
                                        data->count, ev.duration);
                        data->state = STATE_LEADER_PULSE;

                        return 0;

                } else if (geq_margin(ev.duration, XMP_NIBBLE_PREFIX, XMP_UNIT)) {
                        /* store nibble raw data, decode after trailer */
                        if (data->count == 16) {
                                dev_dbg(&dev->dev, "too many pulses (%d) ignoring: %u\n",
                                        data->count, ev.duration);
                                data->state = STATE_INACTIVE;
                                return -EINVAL;
                        }
                        data->durations[data->count] = ev.duration;
                        data->count++;
                        data->state = STATE_LEADER_PULSE;

                        return 0;

                }

                break;
        }

        dev_dbg(&dev->dev, "XMP decode failed at count %d state %d (%uus %s)\n",
                data->count, data->state, ev.duration, TO_STR(ev.pulse));
        data->state = STATE_INACTIVE;
        return -EINVAL;
}

static struct ir_raw_handler xmp_handler = {
        .protocols      = RC_PROTO_BIT_XMP,
        .decode         = ir_xmp_decode,
        .min_timeout    = XMP_TRAILER_SPACE,
};

static int __init ir_xmp_decode_init(void)
{
        ir_raw_handler_register(&xmp_handler);

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

static void __exit ir_xmp_decode_exit(void)
{
        ir_raw_handler_unregister(&xmp_handler);
}

module_init(ir_xmp_decode_init);
module_exit(ir_xmp_decode_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Marcel Mol <marcel@mesa.nl>");
MODULE_AUTHOR("MESA Consulting (http://www.mesa.nl)");
MODULE_DESCRIPTION("XMP IR protocol decoder");