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/printk.h> 13 #include <linux/ratelimit.h> 14 #include <linux/types.h> 15 #include <linux/math64.h> 16 #include <asm/byteorder.h> 17 18 #include "vidtv_ts.h" 19 #include "vidtv_common.h" 20 21 static u32 vidtv_ts_write_pcr_bits(u8 *to, u32 to_offset, u64 pcr) 22 { 23 /* Exact same from ffmpeg. PCR is a counter driven by a 27Mhz clock */ 24 u64 div; 25 u64 rem; 26 u8 *buf = to + to_offset; 27 u64 pcr_low; 28 u64 pcr_high; 29 30 div = div64_u64_rem(pcr, 300, &rem); 31 32 pcr_low = rem; /* pcr_low = pcr % 300 */ 33 pcr_high = div; /* pcr_high = pcr / 300 */ 34 35 *buf++ = pcr_high >> 25; 36 *buf++ = pcr_high >> 17; 37 *buf++ = pcr_high >> 9; 38 *buf++ = pcr_high >> 1; 39 *buf++ = pcr_high << 7 | pcr_low >> 8 | 0x7e; 40 *buf++ = pcr_low; 41 42 return 6; 43 } 44 45 void vidtv_ts_inc_cc(u8 *continuity_counter) 46 { 47 ++*continuity_counter; 48 if (*continuity_counter > TS_CC_MAX_VAL) 49 *continuity_counter = 0; 50 } 51 52 u32 vidtv_ts_null_write_into(struct null_packet_write_args args) 53 { 54 u32 nbytes = 0; 55 struct vidtv_mpeg_ts ts_header = {}; 56 57 ts_header.sync_byte = TS_SYNC_BYTE; 58 ts_header.bitfield = cpu_to_be16(TS_NULL_PACKET_PID); 59 ts_header.payload = 1; 60 ts_header.continuity_counter = *args.continuity_counter; 61 62 /* copy TS header */ 63 nbytes += vidtv_memcpy(args.dest_buf, 64 args.dest_offset + nbytes, 65 args.buf_sz, 66 &ts_header, 67 sizeof(ts_header)); 68 69 vidtv_ts_inc_cc(args.continuity_counter); 70 71 /* fill the rest with empty data */ 72 nbytes += vidtv_memset(args.dest_buf, 73 args.dest_offset + nbytes, 74 args.buf_sz, 75 TS_FILL_BYTE, 76 TS_PACKET_LEN - nbytes); 77 78 /* we should have written exactly _one_ 188byte packet */ 79 if (nbytes != TS_PACKET_LEN) 80 pr_warn_ratelimited("Expected exactly %d bytes, got %d\n", 81 TS_PACKET_LEN, 82 nbytes); 83 84 return nbytes; 85 } 86 87 u32 vidtv_ts_pcr_write_into(struct pcr_write_args args) 88 { 89 u32 nbytes = 0; 90 struct vidtv_mpeg_ts ts_header = {}; 91 struct vidtv_mpeg_ts_adaption ts_adap = {}; 92 93 ts_header.sync_byte = TS_SYNC_BYTE; 94 ts_header.bitfield = cpu_to_be16(args.pid); 95 ts_header.scrambling = 0; 96 /* cc is not incremented, but it is needed. see 13818-1 clause 2.4.3.3 */ 97 ts_header.continuity_counter = *args.continuity_counter; 98 ts_header.payload = 0; 99 ts_header.adaptation_field = 1; 100 101 /* 13818-1 clause 2.4.3.5 */ 102 ts_adap.length = 183; 103 ts_adap.PCR = 1; 104 105 /* copy TS header */ 106 nbytes += vidtv_memcpy(args.dest_buf, 107 args.dest_offset + nbytes, 108 args.buf_sz, 109 &ts_header, 110 sizeof(ts_header)); 111 112 /* write the adap after the TS header */ 113 nbytes += vidtv_memcpy(args.dest_buf, 114 args.dest_offset + nbytes, 115 args.buf_sz, 116 &ts_adap, 117 sizeof(ts_adap)); 118 119 /* write the PCR optional */ 120 nbytes += vidtv_ts_write_pcr_bits(args.dest_buf, 121 args.dest_offset + nbytes, 122 args.pcr); 123 124 nbytes += vidtv_memset(args.dest_buf, 125 args.dest_offset + nbytes, 126 args.buf_sz, 127 TS_FILL_BYTE, 128 TS_PACKET_LEN - nbytes); 129 130 /* we should have written exactly _one_ 188byte packet */ 131 if (nbytes != TS_PACKET_LEN) 132 pr_warn_ratelimited("Expected exactly %d bytes, got %d\n", 133 TS_PACKET_LEN, 134 nbytes); 135 136 return nbytes; 137 } 138