1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * The Virtual DVB test driver serves as a reference DVB driver and helps
4  * validate the existing APIs in the media subsystem. It can also aid
5  * developers working on userspace applications.
6  *
7  * Copyright (C) 2020 Daniel W. S. Almeida
8  */
9 
10 #define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
11 
12 #include <linux/math64.h>
13 #include <linux/printk.h>
14 #include <linux/ratelimit.h>
15 #include <linux/types.h>
16 
17 #include "vidtv_common.h"
18 #include "vidtv_ts.h"
19 
20 static u32 vidtv_ts_write_pcr_bits(u8 *to, u32 to_offset, u64 pcr)
21 {
22 	/* Exact same from ffmpeg. PCR is a counter driven by a 27Mhz clock */
23 	u64 div;
24 	u64 rem;
25 	u8 *buf = to + to_offset;
26 	u64 pcr_low;
27 	u64 pcr_high;
28 
29 	div = div64_u64_rem(pcr, 300, &rem);
30 
31 	pcr_low = rem; /* pcr_low = pcr % 300 */
32 	pcr_high = div; /* pcr_high = pcr / 300 */
33 
34 	*buf++ = pcr_high >> 25;
35 	*buf++ = pcr_high >> 17;
36 	*buf++ = pcr_high >>  9;
37 	*buf++ = pcr_high >>  1;
38 	*buf++ = pcr_high <<  7 | pcr_low >> 8 | 0x7e;
39 	*buf++ = pcr_low;
40 
41 	return 6;
42 }
43 
44 void vidtv_ts_inc_cc(u8 *continuity_counter)
45 {
46 	++*continuity_counter;
47 	if (*continuity_counter > TS_CC_MAX_VAL)
48 		*continuity_counter = 0;
49 }
50 
51 u32 vidtv_ts_null_write_into(struct null_packet_write_args args)
52 {
53 	u32 nbytes = 0;
54 	struct vidtv_mpeg_ts ts_header = {};
55 
56 	ts_header.sync_byte          = TS_SYNC_BYTE;
57 	ts_header.bitfield           = cpu_to_be16(TS_NULL_PACKET_PID);
58 	ts_header.payload            = 1;
59 	ts_header.continuity_counter = *args.continuity_counter;
60 
61 	/* copy TS header */
62 	nbytes += vidtv_memcpy(args.dest_buf,
63 			       args.dest_offset + nbytes,
64 			       args.buf_sz,
65 			       &ts_header,
66 			       sizeof(ts_header));
67 
68 	vidtv_ts_inc_cc(args.continuity_counter);
69 
70 	/* fill the rest with empty data */
71 	nbytes += vidtv_memset(args.dest_buf,
72 			       args.dest_offset + nbytes,
73 			       args.buf_sz,
74 			       TS_FILL_BYTE,
75 			       TS_PACKET_LEN - nbytes);
76 
77 	/* we should have written exactly _one_ 188byte packet */
78 	if (nbytes != TS_PACKET_LEN)
79 		pr_warn_ratelimited("Expected exactly %d bytes, got %d\n",
80 				    TS_PACKET_LEN,
81 				    nbytes);
82 
83 	return nbytes;
84 }
85 
86 u32 vidtv_ts_pcr_write_into(struct pcr_write_args args)
87 {
88 	u32 nbytes = 0;
89 	struct vidtv_mpeg_ts ts_header = {};
90 	struct vidtv_mpeg_ts_adaption ts_adap = {};
91 
92 	ts_header.sync_byte     = TS_SYNC_BYTE;
93 	ts_header.bitfield      = cpu_to_be16(args.pid);
94 	ts_header.scrambling    = 0;
95 	/* cc is not incremented, but it is needed. see 13818-1 clause 2.4.3.3 */
96 	ts_header.continuity_counter = *args.continuity_counter;
97 	ts_header.payload            = 0;
98 	ts_header.adaptation_field   = 1;
99 
100 	/* 13818-1 clause 2.4.3.5 */
101 	ts_adap.length = 183;
102 	ts_adap.PCR    = 1;
103 
104 	/* copy TS header */
105 	nbytes += vidtv_memcpy(args.dest_buf,
106 			       args.dest_offset + nbytes,
107 			       args.buf_sz,
108 			       &ts_header,
109 			       sizeof(ts_header));
110 
111 	/* write the adap after the TS header */
112 	nbytes += vidtv_memcpy(args.dest_buf,
113 			       args.dest_offset + nbytes,
114 			       args.buf_sz,
115 			       &ts_adap,
116 			       sizeof(ts_adap));
117 
118 	/* write the PCR optional */
119 	nbytes += vidtv_ts_write_pcr_bits(args.dest_buf,
120 					  args.dest_offset + nbytes,
121 					  args.pcr);
122 
123 	nbytes += vidtv_memset(args.dest_buf,
124 			       args.dest_offset + nbytes,
125 			       args.buf_sz,
126 			       TS_FILL_BYTE,
127 			       TS_PACKET_LEN - nbytes);
128 
129 	/* we should have written exactly _one_ 188byte packet */
130 	if (nbytes != TS_PACKET_LEN)
131 		pr_warn_ratelimited("Expected exactly %d bytes, got %d\n",
132 				    TS_PACKET_LEN,
133 				    nbytes);
134 
135 	return nbytes;
136 }
137