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 
15 static 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  */
42 void 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 
129 void 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, ((freq & 0xf) * 10) / 16);
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 }
158