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
20static 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
44void 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
51u32 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
86u32 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