parse-vtb-ext-block.cpp

   1 // SPDX-License-Identifier: MIT
   2 /*
   3  * Copyright 2019-2020 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
   4  *
   5  * Author: Hans Verkuil <hverkuil-cisco@xs4all.nl>
   6  */
   7
   8 #include "edid-decode.h"
   9
  10 void edid_state::parse_vtb_ext_block(const unsigned char *x)
  11 {
  12         printf("  Version: %u\n", x[1]);
  13         if (x[1] != 1)
  14                 fail("Invalid version %u.\n", x[1]);
  15
  16         unsigned num_dtd = x[2];
  17         unsigned num_cvt = x[3];
  18         unsigned num_st = x[4];
  19
  20         const unsigned char *y = x + 0x7f;
  21         x += 5;
  22         if (num_dtd) {
  23                 printf("  Detailed Timing Descriptors:\n");
  24                 for (unsigned i = 0; i < num_dtd; i++, x += 18) {
  25                         if (x + 18 > y) {
  26                                 fail("Not enough bytes remain for more DTDs in the VTB-EXT.\n");
  27                                 return;
  28                         }
  29                         detailed_timings("    ", x, false);
  30                 }
  31         }
  32         if (num_cvt) {
  33                 printf("  Coordinated Video Timings:\n");
  34                 for (unsigned i = 0; i < num_cvt; i++, x += 3) {
  35                         if (x + 3 > y) {
  36                                 fail("Not enough bytes remain for more CVTs in the VTB-EXT.\n");
  37                                 return;
  38                         }
  39                         detailed_cvt_descriptor("    ", x, false);
  40                 }
  41         }
  42         if (num_st) {
  43                 // Note: the VTB-EXT standard has a mistake in the example EDID
  44                 // that it provides: there the refresh rate (bits 5-0 of the
  45                 // second byte) is set to 60 for 60 Hz, but this should be 0
  46                 // since the actual refresh rate is the value + 60.
  47                 //
  48                 // The documentation itself is correct, though.
  49                 printf("  Standard Timings:\n");
  50                 for (unsigned i = 0; i < num_st; i++, x += 2) {
  51                         if (x + 2 > y) {
  52                                 fail("Not enough bytes remain for more STs in the VTB-EXT.\n");
  53                                 return;
  54                         }
  55                         print_standard_timing("    ", x[0], x[1], true);
  56                 }
  57         }
  58         unused_bytes = y - x;
  59         if (!memchk(x, unused_bytes)) {
  60                 data_block = "Padding";
  61                 fail("Contains non-zero bytes.\n");
  62         }
  63 }