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

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

#include "vivid-rds-gen.h"

static u8 vivid_get_di(const struct vivid_rds_gen *rds, unsigned grp)
{
        switch (grp) {
        case 0:
                return (rds->dyn_pty << 2) | (grp & 3);
        case 1:
                return (rds->compressed << 2) | (grp & 3);
        case 2:
                return (rds->art_head << 2) | (grp & 3);
        case 3:
                return (rds->mono_stereo << 2) | (grp & 3);
        }
        return 0;
}

/*
 * This RDS generator creates 57 RDS groups (one group == four RDS blocks).
 * Groups 0-3, 22-25 and 44-47 (spaced 22 groups apart) are filled with a
 * standard 0B group containing the PI code and PS name.
 *
 * Groups 4-19 and 26-41 use group 2A for the radio text.
 *
 * Group 56 contains the time (group 4A).
 *
 * All remaining groups use a filler group 15B block that just repeats
 * the PI and PTY codes.
 */
void vivid_rds_generate(struct vivid_rds_gen *rds)
{
        struct v4l2_rds_data *data = rds->data;
        unsigned grp;
        unsigned idx;
        struct tm tm;
        unsigned date;
        unsigned time;
        int l;

        for (grp = 0; grp < VIVID_RDS_GEN_GROUPS; grp++, data += VIVID_RDS_GEN_BLKS_PER_GRP) {
                data[0].lsb = rds->picode & 0xff;
                data[0].msb = rds->picode >> 8;
                data[0].block = V4L2_RDS_BLOCK_A | (V4L2_RDS_BLOCK_A << 3);
                data[1].lsb = rds->pty << 5;
                data[1].msb = (rds->pty >> 3) | (rds->tp << 2);
                data[1].block = V4L2_RDS_BLOCK_B | (V4L2_RDS_BLOCK_B << 3);
                data[3].block = V4L2_RDS_BLOCK_D | (V4L2_RDS_BLOCK_D << 3);

                switch (grp) {
                case 0 ... 3:
                case 22 ... 25:
                case 44 ... 47: /* Group 0B */
                        idx = (grp % 22) % 4;
                        data[1].lsb |= (rds->ta << 4) | (rds->ms << 3);
                        data[1].lsb |= vivid_get_di(rds, idx);
                        data[1].msb |= 1 << 3;
                        data[2].lsb = rds->picode & 0xff;
                        data[2].msb = rds->picode >> 8;
                        data[2].block = V4L2_RDS_BLOCK_C_ALT | (V4L2_RDS_BLOCK_C_ALT << 3);
                        data[3].lsb = rds->psname[2 * idx + 1];
                        data[3].msb = rds->psname[2 * idx];
                        break;
                case 4 ... 19:
                case 26 ... 41: /* Group 2A */
                        idx = ((grp - 4) % 22) % 16;
                        data[1].lsb |= idx;
                        data[1].msb |= 4 << 3;
                        data[2].msb = rds->radiotext[4 * idx];
                        data[2].lsb = rds->radiotext[4 * idx + 1];
                        data[2].block = V4L2_RDS_BLOCK_C | (V4L2_RDS_BLOCK_C << 3);
                        data[3].msb = rds->radiotext[4 * idx + 2];
                        data[3].lsb = rds->radiotext[4 * idx + 3];
                        break;
                case 56:
                        /*
                         * Group 4A
                         *
                         * Uses the algorithm from Annex G of the RDS standard
                         * EN 50067:1998 to convert a UTC date to an RDS Modified
                         * Julian Day.
                         */
                        time64_to_tm(ktime_get_real_seconds(), 0, &tm);
                        l = tm.tm_mon <= 1;
                        date = 14956 + tm.tm_mday + ((tm.tm_year - l) * 1461) / 4 +
                                ((tm.tm_mon + 2 + l * 12) * 306001) / 10000;
                        time = (tm.tm_hour << 12) |
                               (tm.tm_min << 6) |
                               (sys_tz.tz_minuteswest >= 0 ? 0x20 : 0) |
                               (abs(sys_tz.tz_minuteswest) / 30);
                        data[1].lsb &= ~3;
                        data[1].lsb |= date >> 15;
                        data[1].msb |= 8 << 3;
                        data[2].lsb = (date << 1) & 0xfe;
                        data[2].lsb |= (time >> 16) & 1;
                        data[2].msb = (date >> 7) & 0xff;
                        data[2].block = V4L2_RDS_BLOCK_C | (V4L2_RDS_BLOCK_C << 3);
                        data[3].lsb = time & 0xff;
                        data[3].msb = (time >> 8) & 0xff;
                        break;
                default: /* Group 15B */
                        data[1].lsb |= (rds->ta << 4) | (rds->ms << 3);
                        data[1].lsb |= vivid_get_di(rds, grp % 22);
                        data[1].msb |= 0x1f << 3;
                        data[2].lsb = rds->picode & 0xff;
                        data[2].msb = rds->picode >> 8;
                        data[2].block = V4L2_RDS_BLOCK_C_ALT | (V4L2_RDS_BLOCK_C_ALT << 3);
                        data[3].lsb = rds->pty << 5;
                        data[3].lsb |= (rds->ta << 4) | (rds->ms << 3);
                        data[3].lsb |= vivid_get_di(rds, grp % 22);
                        data[3].msb |= rds->pty >> 3;
                        data[3].msb |= 0x1f << 3;
                        break;
                }
        }
}

void vivid_rds_gen_fill(struct vivid_rds_gen *rds, unsigned freq,
                          bool alt)
{
        /* Alternate PTY between Info and Weather */
        if (rds->use_rbds) {
                rds->picode = 0x2e75; /* 'KLNX' call sign */
                rds->pty = alt ? 29 : 2;
        } else {
                rds->picode = 0x8088;
                rds->pty = alt ? 16 : 3;
        }
        rds->mono_stereo = true;
        rds->art_head = false;
        rds->compressed = false;
        rds->dyn_pty = false;
        rds->tp = true;
        rds->ta = alt;
        rds->ms = true;
        snprintf(rds->psname, sizeof(rds->psname), "%6d.%1d",
                 freq / 16, ((freq & 0xf) * 10) / 16);
        if (alt)
                strscpy(rds->radiotext,
                        " The Radio Data System can switch between different Radio Texts ",
                        sizeof(rds->radiotext));
        else
                strscpy(rds->radiotext,
                        "An example of Radio Text as transmitted by the Radio Data System",
                        sizeof(rds->radiotext));
}