vivid-rds-gen.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * vivid-rds-gen.c - rds (radio data system) generator support functions.
  4 *
  5 * Copyright 2014 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
  6 */
  7
  8#include <linux/kernel.h>
  9#include <linux/ktime.h>
 10#include <linux/string.h>
 11#include <linux/videodev2.h>
 12
 13#include "vivid-rds-gen.h"
 14
 15static u8 vivid_get_di(const struct vivid_rds_gen *rds, unsigned grp)
 16{
 17	switch (grp) {
 18	case 0:
 19		return (rds->dyn_pty << 2) | (grp & 3);
 20	case 1:
 21		return (rds->compressed << 2) | (grp & 3);
 22	case 2:
 23		return (rds->art_head << 2) | (grp & 3);
 24	case 3:
 25		return (rds->mono_stereo << 2) | (grp & 3);
 26	}
 27	return 0;
 28}
 29
 30/*
 31 * This RDS generator creates 57 RDS groups (one group == four RDS blocks).
 32 * Groups 0-3, 22-25 and 44-47 (spaced 22 groups apart) are filled with a
 33 * standard 0B group containing the PI code and PS name.
 34 *
 35 * Groups 4-19 and 26-41 use group 2A for the radio text.
 36 *
 37 * Group 56 contains the time (group 4A).
 38 *
 39 * All remaining groups use a filler group 15B block that just repeats
 40 * the PI and PTY codes.
 41 */
 42void vivid_rds_generate(struct vivid_rds_gen *rds)
 43{
 44	struct v4l2_rds_data *data = rds->data;
 45	unsigned grp;
 46	unsigned idx;
 47	struct tm tm;
 48	unsigned date;
 49	unsigned time;
 50	int l;
 51
 52	for (grp = 0; grp < VIVID_RDS_GEN_GROUPS; grp++, data += VIVID_RDS_GEN_BLKS_PER_GRP) {
 53		data[0].lsb = rds->picode & 0xff;
 54		data[0].msb = rds->picode >> 8;
 55		data[0].block = V4L2_RDS_BLOCK_A | (V4L2_RDS_BLOCK_A << 3);
 56		data[1].lsb = rds->pty << 5;
 57		data[1].msb = (rds->pty >> 3) | (rds->tp << 2);
 58		data[1].block = V4L2_RDS_BLOCK_B | (V4L2_RDS_BLOCK_B << 3);
 59		data[3].block = V4L2_RDS_BLOCK_D | (V4L2_RDS_BLOCK_D << 3);
 60
 61		switch (grp) {
 62		case 0 ... 3:
 63		case 22 ... 25:
 64		case 44 ... 47: /* Group 0B */
 65			idx = (grp % 22) % 4;
 66			data[1].lsb |= (rds->ta << 4) | (rds->ms << 3);
 67			data[1].lsb |= vivid_get_di(rds, idx);
 68			data[1].msb |= 1 << 3;
 69			data[2].lsb = rds->picode & 0xff;
 70			data[2].msb = rds->picode >> 8;
 71			data[2].block = V4L2_RDS_BLOCK_C_ALT | (V4L2_RDS_BLOCK_C_ALT << 3);
 72			data[3].lsb = rds->psname[2 * idx + 1];
 73			data[3].msb = rds->psname[2 * idx];
 74			break;
 75		case 4 ... 19:
 76		case 26 ... 41: /* Group 2A */
 77			idx = ((grp - 4) % 22) % 16;
 78			data[1].lsb |= idx;
 79			data[1].msb |= 4 << 3;
 80			data[2].msb = rds->radiotext[4 * idx];
 81			data[2].lsb = rds->radiotext[4 * idx + 1];
 82			data[2].block = V4L2_RDS_BLOCK_C | (V4L2_RDS_BLOCK_C << 3);
 83			data[3].msb = rds->radiotext[4 * idx + 2];
 84			data[3].lsb = rds->radiotext[4 * idx + 3];
 85			break;
 86		case 56:
 87			/*
 88			 * Group 4A
 89			 *
 90			 * Uses the algorithm from Annex G of the RDS standard
 91			 * EN 50067:1998 to convert a UTC date to an RDS Modified
 92			 * Julian Day.
 93			 */
 94			time64_to_tm(ktime_get_real_seconds(), 0, &tm);
 95			l = tm.tm_mon <= 1;
 96			date = 14956 + tm.tm_mday + ((tm.tm_year - l) * 1461) / 4 +
 97				((tm.tm_mon + 2 + l * 12) * 306001) / 10000;
 98			time = (tm.tm_hour << 12) |
 99			       (tm.tm_min << 6) |
100			       (sys_tz.tz_minuteswest >= 0 ? 0x20 : 0) |
101			       (abs(sys_tz.tz_minuteswest) / 30);
102			data[1].lsb &= ~3;
103			data[1].lsb |= date >> 15;
104			data[1].msb |= 8 << 3;
105			data[2].lsb = (date << 1) & 0xfe;
106			data[2].lsb |= (time >> 16) & 1;
107			data[2].msb = (date >> 7) & 0xff;
108			data[2].block = V4L2_RDS_BLOCK_C | (V4L2_RDS_BLOCK_C << 3);
109			data[3].lsb = time & 0xff;
110			data[3].msb = (time >> 8) & 0xff;
111			break;
112		default: /* Group 15B */
113			data[1].lsb |= (rds->ta << 4) | (rds->ms << 3);
114			data[1].lsb |= vivid_get_di(rds, grp % 22);
115			data[1].msb |= 0x1f << 3;
116			data[2].lsb = rds->picode & 0xff;
117			data[2].msb = rds->picode >> 8;
118			data[2].block = V4L2_RDS_BLOCK_C_ALT | (V4L2_RDS_BLOCK_C_ALT << 3);
119			data[3].lsb = rds->pty << 5;
120			data[3].lsb |= (rds->ta << 4) | (rds->ms << 3);
121			data[3].lsb |= vivid_get_di(rds, grp % 22);
122			data[3].msb |= rds->pty >> 3;
123			data[3].msb |= 0x1f << 3;
124			break;
125		}
126	}
127}
128
129void vivid_rds_gen_fill(struct vivid_rds_gen *rds, unsigned freq,
130			  bool alt)
131{
132	/* Alternate PTY between Info and Weather */
133	if (rds->use_rbds) {
134		rds->picode = 0x2e75; /* 'KLNX' call sign */
135		rds->pty = alt ? 29 : 2;
136	} else {
137		rds->picode = 0x8088;
138		rds->pty = alt ? 16 : 3;
139	}
140	rds->mono_stereo = true;
141	rds->art_head = false;
142	rds->compressed = false;
143	rds->dyn_pty = false;
144	rds->tp = true;
145	rds->ta = alt;
146	rds->ms = true;
147	snprintf(rds->psname, sizeof(rds->psname), "%6d.%1d",
148		 (freq / 16) % 1000000, (((freq & 0xf) * 10) / 16) % 10);
149	if (alt)
150		strscpy(rds->radiotext,
151			" The Radio Data System can switch between different Radio Texts ",
152			sizeof(rds->radiotext));
153	else
154		strscpy(rds->radiotext,
155			"An example of Radio Text as transmitted by the Radio Data System",
156			sizeof(rds->radiotext));
157}