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