// SPDX-License-Identifier: GPL-2.0
// ir-nec-decoder.c - handle NEC IR Pulse/Space protocol
//
// Copyright (C) 2010 by Mauro Carvalho Chehab

#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,
};

/**
 * ir_nec_decode() - Decode one NEC 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_nec_decode(struct rc_dev *dev, struct ir_raw_event ev)
{
        struct nec_dec *data = &dev->raw->nec;
        u32 scancode;
        enum rc_proto rc_proto;
        u8 address, not_address, command, not_command;

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

        dev_dbg(&dev->dev, "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)) {
                        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)) {
                        dev_dbg(&dev->dev, "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;

                if (data->count == NEC_NBITS) {
                        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);

                        scancode = ir_nec_bytes_to_scancode(address,
                                                            not_address,
                                                            command,
                                                            not_command,
                                                            &rc_proto);

                        if (data->is_nec_x)
                                data->necx_repeat = true;

                        rc_keydown(dev, rc_proto, scancode, 0);
                } else {
                        rc_repeat(dev);
                }

                data->state = STATE_INACTIVE;
                return 0;
        }

        dev_dbg(&dev->dev, "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;
}

/**
 * ir_nec_scancode_to_raw() - encode an NEC scancode ready for modulation.
 * @protocol:   specific protocol to use
 * @scancode:   a single NEC scancode.
 */
static u32 ir_nec_scancode_to_raw(enum rc_proto protocol, u32 scancode)
{
        unsigned int addr, addr_inv, data, data_inv;

        data = scancode & 0xff;

        if (protocol == RC_PROTO_NEC32) {
                /* 32-bit NEC (used by Apple and TiVo remotes) */
                /* scan encoding: aaAAddDD */
                addr_inv   = (scancode >> 24) & 0xff;
                addr       = (scancode >> 16) & 0xff;
                data_inv   = (scancode >>  8) & 0xff;
        } else if (protocol == RC_PROTO_NECX) {
                /* Extended NEC */
                /* scan encoding AAaaDD */
                addr       = (scancode >> 16) & 0xff;
                addr_inv   = (scancode >>  8) & 0xff;
                data_inv   = data ^ 0xff;
        } else {
                /* Normal NEC */
                /* scan encoding: AADD */
                addr       = (scancode >>  8) & 0xff;
                addr_inv   = addr ^ 0xff;
                data_inv   = data ^ 0xff;
        }

        /* raw encoding: ddDDaaAA */
        return data_inv << 24 |
               data     << 16 |
               addr_inv <<  8 |
               addr;
}

static const struct ir_raw_timings_pd ir_nec_timings = {
        .header_pulse   = NEC_HEADER_PULSE,
        .header_space   = NEC_HEADER_SPACE,
        .bit_pulse      = NEC_BIT_PULSE,
        .bit_space[0]   = NEC_BIT_0_SPACE,
        .bit_space[1]   = NEC_BIT_1_SPACE,
        .trailer_pulse  = NEC_TRAILER_PULSE,
        .trailer_space  = NEC_TRAILER_SPACE,
        .msb_first      = 0,
};

/**
 * ir_nec_encode() - Encode a scancode as a stream of raw events
 *
 * @protocol:   protocol 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.
 */
static int ir_nec_encode(enum rc_proto protocol, u32 scancode,
                         struct ir_raw_event *events, unsigned int max)
{
        struct ir_raw_event *e = events;
        int ret;
        u32 raw;

        /* Convert a NEC scancode to raw NEC data */
        raw = ir_nec_scancode_to_raw(protocol, scancode);

        /* Modulate the raw data using a pulse distance modulation */
        ret = ir_raw_gen_pd(&e, max, &ir_nec_timings, NEC_NBITS, raw);
        if (ret < 0)
                return ret;

        return e - events;
}

static struct ir_raw_handler nec_handler = {
        .protocols      = RC_PROTO_BIT_NEC | RC_PROTO_BIT_NECX |
                                                        RC_PROTO_BIT_NEC32,
        .decode         = ir_nec_decode,
        .encode         = ir_nec_encode,
        .carrier        = 38000,
        .min_timeout    = NEC_TRAILER_SPACE,
};

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 v2");
MODULE_AUTHOR("Mauro Carvalho Chehab");
MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
MODULE_DESCRIPTION("NEC IR protocol decoder");