// SPDX-License-Identifier: GPL-2.0-only
/*
 * vivid-vbi-gen.c - vbi generator support functions.
 *
 * Copyright 2014 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
 */

#include <linux/bitops.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/ktime.h>
#include <linux/string.h>
#include <linux/videodev2.h>

#include "vivid-vbi-gen.h"

static void wss_insert(u8 *wss, u32 val, unsigned size)
{
        while (size--)
                *wss++ = (val & (1 << size)) ? 0xc0 : 0x10;
}

static void vivid_vbi_gen_wss_raw(const struct v4l2_sliced_vbi_data *data,
                u8 *buf, unsigned sampling_rate)
{
        const unsigned rate = 5000000;  /* WSS has a 5 MHz transmission rate */
        u8 wss[29 + 24 + 24 + 24 + 18 + 18] = { 0 };
        const unsigned zero = 0x07;
        const unsigned one = 0x38;
        unsigned bit = 0;
        u16 wss_data;
        int i;

        wss_insert(wss + bit, 0x1f1c71c7, 29); bit += 29;
        wss_insert(wss + bit, 0x1e3c1f, 24); bit += 24;

        wss_data = (data->data[1] << 8) | data->data[0];
        for (i = 0; i <= 13; i++, bit += 6)
                wss_insert(wss + bit, (wss_data & (1 << i)) ? one : zero, 6);

        for (i = 0, bit = 0; bit < sizeof(wss); bit++) {
                unsigned n = ((bit + 1) * sampling_rate) / rate;

                while (i < n)
                        buf[i++] = wss[bit];
        }
}

static void vivid_vbi_gen_teletext_raw(const struct v4l2_sliced_vbi_data *data,
                u8 *buf, unsigned sampling_rate)
{
        const unsigned rate = 6937500 / 10;     /* Teletext has a 6.9375 MHz transmission rate */
        u8 teletext[45] = { 0x55, 0x55, 0x27 };
        unsigned bit = 0;
        int i;

        memcpy(teletext + 3, data->data, sizeof(teletext) - 3);
        /* prevents 32 bit overflow */
        sampling_rate /= 10;

        for (i = 0, bit = 0; bit < sizeof(teletext) * 8; bit++) {
                unsigned n = ((bit + 1) * sampling_rate) / rate;
                u8 val = (teletext[bit / 8] & (1 << (bit & 7))) ? 0xc0 : 0x10;

                while (i < n)
                        buf[i++] = val;
        }
}

static void cc_insert(u8 *cc, u8 ch)
{
        unsigned tot = 0;
        unsigned i;

        for (i = 0; i < 7; i++) {
                cc[2 * i] = cc[2 * i + 1] = (ch & (1 << i)) ? 1 : 0;
                tot += cc[2 * i];
        }
        cc[14] = cc[15] = !(tot & 1);
}

#define CC_PREAMBLE_BITS (14 + 4 + 2)

static void vivid_vbi_gen_cc_raw(const struct v4l2_sliced_vbi_data *data,
                u8 *buf, unsigned sampling_rate)
{
        const unsigned rate = 1000000;  /* CC has a 1 MHz transmission rate */

        u8 cc[CC_PREAMBLE_BITS + 2 * 16] = {
                /* Clock run-in: 7 cycles */
                0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1,
                /* 2 cycles of 0 */
                0, 0, 0, 0,
                /* Start bit of 1 (each bit is two cycles) */
                1, 1
        };
        unsigned bit, i;

        cc_insert(cc + CC_PREAMBLE_BITS, data->data[0]);
        cc_insert(cc + CC_PREAMBLE_BITS + 16, data->data[1]);

        for (i = 0, bit = 0; bit < sizeof(cc); bit++) {
                unsigned n = ((bit + 1) * sampling_rate) / rate;

                while (i < n)
                        buf[i++] = cc[bit] ? 0xc0 : 0x10;
        }
}

void vivid_vbi_gen_raw(const struct vivid_vbi_gen_data *vbi,
                const struct v4l2_vbi_format *vbi_fmt, u8 *buf)
{
        unsigned idx;

        for (idx = 0; idx < 25; idx++) {
                const struct v4l2_sliced_vbi_data *data = vbi->data + idx;
                unsigned start_2nd_field;
                unsigned line = data->line;
                u8 *linebuf = buf;

                start_2nd_field = (data->id & V4L2_SLICED_VBI_525) ? 263 : 313;
                if (data->field)
                        line += start_2nd_field;
                line -= vbi_fmt->start[data->field];

                if (vbi_fmt->flags & V4L2_VBI_INTERLACED)
                        linebuf += (line * 2 + data->field) *
                                vbi_fmt->samples_per_line;
                else
                        linebuf += (line + data->field * vbi_fmt->count[0]) *
                                vbi_fmt->samples_per_line;
                if (data->id == V4L2_SLICED_CAPTION_525)
                        vivid_vbi_gen_cc_raw(data, linebuf, vbi_fmt->sampling_rate);
                else if (data->id == V4L2_SLICED_WSS_625)
                        vivid_vbi_gen_wss_raw(data, linebuf, vbi_fmt->sampling_rate);
                else if (data->id == V4L2_SLICED_TELETEXT_B)
                        vivid_vbi_gen_teletext_raw(data, linebuf, vbi_fmt->sampling_rate);
        }
}

static const u8 vivid_cc_sequence1[30] = {
        0x14, 0x20,     /* Resume Caption Loading */
        'H',  'e',
        'l',  'l',
        'o',  ' ',
        'w',  'o',
        'r',  'l',
        'd',  '!',
        0x14, 0x2f,     /* End of Caption */
};

static const u8 vivid_cc_sequence2[30] = {
        0x14, 0x20,     /* Resume Caption Loading */
        'C',  'l',
        'o',  's',
        'e',  'd',
        ' ',  'c',
        'a',  'p',
        't',  'i',
        'o',  'n',
        's',  ' ',
        't',  'e',
        's',  't',
        0x14, 0x2f,     /* End of Caption */
};

static u8 calc_parity(u8 val)
{
        return val | (parity8(val) ? 0 : 0x80);
}

static void vivid_vbi_gen_set_time_of_day(u8 *packet)
{
        struct tm tm;
        u8 checksum, i;

        time64_to_tm(ktime_get_real_seconds(), 0, &tm);
        packet[0] = calc_parity(0x07);
        packet[1] = calc_parity(0x01);
        packet[2] = calc_parity(0x40 | tm.tm_min);
        packet[3] = calc_parity(0x40 | tm.tm_hour);
        packet[4] = calc_parity(0x40 | tm.tm_mday);
        if (tm.tm_mday == 1 && tm.tm_mon == 2 &&
            sys_tz.tz_minuteswest > tm.tm_min + tm.tm_hour * 60)
                packet[4] = calc_parity(0x60 | tm.tm_mday);
        packet[5] = calc_parity(0x40 | (1 + tm.tm_mon));
        packet[6] = calc_parity(0x40 | (1 + tm.tm_wday));
        packet[7] = calc_parity(0x40 | ((tm.tm_year - 90) & 0x3f));
        packet[8] = calc_parity(0x0f);
        for (checksum = i = 0; i <= 8; i++)
                checksum += packet[i] & 0x7f;
        packet[9] = calc_parity(0x100 - checksum);
        packet[10] = calc_parity(0x07);
        packet[11] = calc_parity(0x04);
        if (sys_tz.tz_minuteswest >= 0)
                packet[12] = calc_parity(0x40 | ((sys_tz.tz_minuteswest / 60) & 0x1f));
        else
                packet[12] = calc_parity(0x40 | ((24 + sys_tz.tz_minuteswest / 60) & 0x1f));
        packet[13] = calc_parity(0);
        packet[14] = calc_parity(0x0f);
        for (checksum = 0, i = 10; i <= 14; i++)
                checksum += packet[i] & 0x7f;
        packet[15] = calc_parity(0x100 - checksum);
}

static const u8 hamming[16] = {
        0x15, 0x02, 0x49, 0x5e, 0x64, 0x73, 0x38, 0x2f,
        0xd0, 0xc7, 0x8c, 0x9b, 0xa1, 0xb6, 0xfd, 0xea
};

static void vivid_vbi_gen_teletext(u8 *packet, unsigned line, unsigned frame)
{
        unsigned offset = 2;
        unsigned i;

        packet[0] = hamming[1 + ((line & 1) << 3)];
        packet[1] = hamming[line >> 1];
        memset(packet + 2, 0x20, 40);
        if (line == 0) {
                /* subcode */
                packet[2] = hamming[frame % 10];
                packet[3] = hamming[frame / 10];
                packet[4] = hamming[0];
                packet[5] = hamming[0];
                packet[6] = hamming[0];
                packet[7] = hamming[0];
                packet[8] = hamming[0];
                packet[9] = hamming[1];
                offset = 10;
        }
        packet += offset;
        memcpy(packet, "Page: 100 Row: 10", 17);
        packet[7] = '0' + frame / 10;
        packet[8] = '0' + frame % 10;
        packet[15] = '0' + line / 10;
        packet[16] = '0' + line % 10;
        for (i = 0; i < 42 - offset; i++)
                packet[i] = calc_parity(packet[i]);
}

void vivid_vbi_gen_sliced(struct vivid_vbi_gen_data *vbi,
                bool is_60hz, unsigned seqnr)
{
        struct v4l2_sliced_vbi_data *data0 = vbi->data;
        struct v4l2_sliced_vbi_data *data1 = vbi->data + 1;
        unsigned frame = seqnr % 60;

        memset(vbi->data, 0, sizeof(vbi->data));

        if (!is_60hz) {
                unsigned i;

                for (i = 0; i <= 11; i++) {
                        data0->id = V4L2_SLICED_TELETEXT_B;
                        data0->line = 7 + i;
                        vivid_vbi_gen_teletext(data0->data, i, frame);
                        data0++;
                }
                data0->id = V4L2_SLICED_WSS_625;
                data0->line = 23;
                /* 4x3 video aspect ratio */
                data0->data[0] = 0x08;
                data0++;
                for (i = 0; i <= 11; i++) {
                        data0->id = V4L2_SLICED_TELETEXT_B;
                        data0->field = 1;
                        data0->line = 7 + i;
                        vivid_vbi_gen_teletext(data0->data, 12 + i, frame);
                        data0++;
                }
                return;
        }

        data0->id = V4L2_SLICED_CAPTION_525;
        data0->line = 21;
        data1->id = V4L2_SLICED_CAPTION_525;
        data1->field = 1;
        data1->line = 21;

        if (frame < 15) {
                data0->data[0] = calc_parity(vivid_cc_sequence1[2 * frame]);
                data0->data[1] = calc_parity(vivid_cc_sequence1[2 * frame + 1]);
        } else if (frame >= 30 && frame < 45) {
                frame -= 30;
                data0->data[0] = calc_parity(vivid_cc_sequence2[2 * frame]);
                data0->data[1] = calc_parity(vivid_cc_sequence2[2 * frame + 1]);
        } else {
                data0->data[0] = calc_parity(0);
                data0->data[1] = calc_parity(0);
        }

        frame = seqnr % (30 * 60);
        switch (frame) {
        case 0:
                vivid_vbi_gen_set_time_of_day(vbi->time_of_day_packet);
                fallthrough;
        case 1 ... 7:
                data1->data[0] = vbi->time_of_day_packet[frame * 2];
                data1->data[1] = vbi->time_of_day_packet[frame * 2 + 1];
                break;
        default:
                data1->data[0] = calc_parity(0);
                data1->data[1] = calc_parity(0);
                break;
        }
}