// SPDX-License-Identifier: GPL-2.0
// ir-rc5-decoder.c - decoder for RC5(x) and StreamZap protocols
//
// Copyright (C) 2010 by Mauro Carvalho Chehab
// Copyright (C) 2010 by Jarod Wilson <jarod@redhat.com>

/*
 * This decoder handles the 14 bit RC5 protocol, 15 bit "StreamZap" protocol
 * and 20 bit RC5x protocol.
 */

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

#define RC5_NBITS               14
#define RC5_SZ_NBITS            15
#define RC5X_NBITS              20
#define CHECK_RC5X_NBITS        8
#define RC5_UNIT                889 /* us */
#define RC5_BIT_START           (1 * RC5_UNIT)
#define RC5_BIT_END             (1 * RC5_UNIT)
#define RC5X_SPACE              (4 * RC5_UNIT)
#define RC5_TRAILER             (6 * RC5_UNIT) /* In reality, approx 100 */

enum rc5_state {
        STATE_INACTIVE,
        STATE_BIT_START,
        STATE_BIT_END,
        STATE_CHECK_RC5X,
        STATE_FINISHED,
};

/**
 * ir_rc5_decode() - Decode one RC-5 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_rc5_decode(struct rc_dev *dev, struct ir_raw_event ev)
{
        struct rc5_dec *data = &dev->raw->rc5;
        u8 toggle;
        u32 scancode;
        enum rc_proto protocol;

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

        if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
                goto out;

again:
        dev_dbg(&dev->dev, "RC5(x/sz) decode started at state %i (%uus %s)\n",
                data->state, ev.duration, TO_STR(ev.pulse));

        if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
                return 0;

        switch (data->state) {

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

                data->state = STATE_BIT_START;
                data->count = 1;
                decrease_duration(&ev, RC5_BIT_START);
                goto again;

        case STATE_BIT_START:
                if (!ev.pulse && geq_margin(ev.duration, RC5_TRAILER, RC5_UNIT / 2)) {
                        data->state = STATE_FINISHED;
                        goto again;
                }

                if (!eq_margin(ev.duration, RC5_BIT_START, RC5_UNIT / 2))
                        break;

                data->bits <<= 1;
                if (!ev.pulse)
                        data->bits |= 1;
                data->count++;
                data->state = STATE_BIT_END;
                return 0;

        case STATE_BIT_END:
                if (data->count == CHECK_RC5X_NBITS)
                        data->state = STATE_CHECK_RC5X;
                else
                        data->state = STATE_BIT_START;

                decrease_duration(&ev, RC5_BIT_END);
                goto again;

        case STATE_CHECK_RC5X:
                if (!ev.pulse && geq_margin(ev.duration, RC5X_SPACE, RC5_UNIT / 2)) {
                        data->is_rc5x = true;
                        decrease_duration(&ev, RC5X_SPACE);
                } else
                        data->is_rc5x = false;
                data->state = STATE_BIT_START;
                goto again;

        case STATE_FINISHED:
                if (ev.pulse)
                        break;

                if (data->is_rc5x && data->count == RC5X_NBITS) {
                        /* RC5X */
                        u8 xdata, command, system;
                        if (!(dev->enabled_protocols & RC_PROTO_BIT_RC5X_20)) {
                                data->state = STATE_INACTIVE;
                                return 0;
                        }
                        xdata    = (data->bits & 0x0003F) >> 0;
                        command  = (data->bits & 0x00FC0) >> 6;
                        system   = (data->bits & 0x1F000) >> 12;
                        toggle   = (data->bits & 0x20000) ? 1 : 0;
                        command += (data->bits & 0x40000) ? 0 : 0x40;
                        scancode = system << 16 | command << 8 | xdata;
                        protocol = RC_PROTO_RC5X_20;

                } else if (!data->is_rc5x && data->count == RC5_NBITS) {
                        /* RC5 */
                        u8 command, system;
                        if (!(dev->enabled_protocols & RC_PROTO_BIT_RC5)) {
                                data->state = STATE_INACTIVE;
                                return 0;
                        }
                        command  = (data->bits & 0x0003F) >> 0;
                        system   = (data->bits & 0x007C0) >> 6;
                        toggle   = (data->bits & 0x00800) ? 1 : 0;
                        command += (data->bits & 0x01000) ? 0 : 0x40;
                        scancode = system << 8 | command;
                        protocol = RC_PROTO_RC5;

                } else if (!data->is_rc5x && data->count == RC5_SZ_NBITS) {
                        /* RC5 StreamZap */
                        u8 command, system;
                        if (!(dev->enabled_protocols & RC_PROTO_BIT_RC5_SZ)) {
                                data->state = STATE_INACTIVE;
                                return 0;
                        }
                        command  = (data->bits & 0x0003F) >> 0;
                        system   = (data->bits & 0x02FC0) >> 6;
                        toggle   = (data->bits & 0x01000) ? 1 : 0;
                        scancode = system << 6 | command;
                        protocol = RC_PROTO_RC5_SZ;

                } else
                        break;

                dev_dbg(&dev->dev, "RC5(x/sz) scancode 0x%06x (p: %u, t: %u)\n",
                        scancode, protocol, toggle);

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

out:
        dev_dbg(&dev->dev, "RC5(x/sz) decode failed at state %i count %d (%uus %s)\n",
                data->state, data->count, ev.duration, TO_STR(ev.pulse));
        data->state = STATE_INACTIVE;
        return -EINVAL;
}

static const struct ir_raw_timings_manchester ir_rc5_timings = {
        .leader_pulse           = RC5_UNIT,
        .clock                  = RC5_UNIT,
        .trailer_space          = RC5_UNIT * 10,
};

static const struct ir_raw_timings_manchester ir_rc5x_timings[2] = {
        {
                .leader_pulse           = RC5_UNIT,
                .clock                  = RC5_UNIT,
                .trailer_space          = RC5X_SPACE,
        },
        {
                .clock                  = RC5_UNIT,
                .trailer_space          = RC5_UNIT * 10,
        },
};

static const struct ir_raw_timings_manchester ir_rc5_sz_timings = {
        .leader_pulse                   = RC5_UNIT,
        .clock                          = RC5_UNIT,
        .trailer_space                  = RC5_UNIT * 10,
};

/**
 * ir_rc5_encode() - Encode a scancode as a stream of raw events
 *
 * @protocol:   protocol variant to encode
 * @scancode:   scancode to encode
 * @events:     array of raw ir events to write into
 * @max:        maximum size of @events
 *
 * Returns:     The number of events written.
 *              -ENOBUFS if there isn't enough space in the array to fit the
 *              encoding. In this case all @max events will have been written.
 *              -EINVAL if the scancode is ambiguous or invalid.
 */
static int ir_rc5_encode(enum rc_proto protocol, u32 scancode,
                         struct ir_raw_event *events, unsigned int max)
{
        int ret;
        struct ir_raw_event *e = events;
        unsigned int data, xdata, command, commandx, system, pre_space_data;

        /* Detect protocol and convert scancode to raw data */
        if (protocol == RC_PROTO_RC5) {
                /* decode scancode */
                command  = (scancode & 0x003f) >> 0;
                commandx = (scancode & 0x0040) >> 6;
                system   = (scancode & 0x1f00) >> 8;
                /* encode data */
                data = !commandx << 12 | system << 6 | command;

                /* First bit is encoded by leader_pulse */
                ret = ir_raw_gen_manchester(&e, max, &ir_rc5_timings,
                                            RC5_NBITS - 1, data);
                if (ret < 0)
                        return ret;
        } else if (protocol == RC_PROTO_RC5X_20) {
                /* decode scancode */
                xdata    = (scancode & 0x00003f) >> 0;
                command  = (scancode & 0x003f00) >> 8;
                commandx = !(scancode & 0x004000);
                system   = (scancode & 0x1f0000) >> 16;

                /* encode data */
                data = commandx << 18 | system << 12 | command << 6 | xdata;

                /* First bit is encoded by leader_pulse */
                pre_space_data = data >> (RC5X_NBITS - CHECK_RC5X_NBITS);
                ret = ir_raw_gen_manchester(&e, max, &ir_rc5x_timings[0],
                                            CHECK_RC5X_NBITS - 1,
                                            pre_space_data);
                if (ret < 0)
                        return ret;
                ret = ir_raw_gen_manchester(&e, max - (e - events),
                                            &ir_rc5x_timings[1],
                                            RC5X_NBITS - CHECK_RC5X_NBITS,
                                            data);
                if (ret < 0)
                        return ret;
        } else if (protocol == RC_PROTO_RC5_SZ) {
                /* RC5-SZ scancode is raw enough for Manchester as it is */
                /* First bit is encoded by leader_pulse */
                ret = ir_raw_gen_manchester(&e, max, &ir_rc5_sz_timings,
                                            RC5_SZ_NBITS - 1,
                                            scancode & 0x2fff);
                if (ret < 0)
                        return ret;
        } else {
                return -EINVAL;
        }

        return e - events;
}

static struct ir_raw_handler rc5_handler = {
        .protocols      = RC_PROTO_BIT_RC5 | RC_PROTO_BIT_RC5X_20 |
                                                        RC_PROTO_BIT_RC5_SZ,
        .decode         = ir_rc5_decode,
        .encode         = ir_rc5_encode,
        .carrier        = 36000,
        .min_timeout    = RC5_TRAILER,
};

static int __init ir_rc5_decode_init(void)
{
        ir_raw_handler_register(&rc5_handler);

        printk(KERN_INFO "IR RC5(x/sz) protocol handler initialized\n");
        return 0;
}

static void __exit ir_rc5_decode_exit(void)
{
        ir_raw_handler_unregister(&rc5_handler);
}

module_init(ir_rc5_decode_init);
module_exit(ir_rc5_decode_exit);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Mauro Carvalho Chehab and Jarod Wilson");
MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
MODULE_DESCRIPTION("RC5(x/sz) IR protocol decoder");