1 /*
2 * SPDX-FileCopyrightText: Copyright (c) 1993-2021 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
3 * SPDX-License-Identifier: MIT
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining a
6 * copy of this software and associated documentation files (the "Software"),
7 * to deal in the Software without restriction, including without limitation
8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 * and/or sell copies of the Software, and to permit persons to whom the
10 * Software is furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be included in
13 * all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
21 * DEALINGS IN THE SOFTWARE.
22 */
23
24 /******************************* DisplayPort*********************************\
25 * *
26 * Module: dp_crc.cpp *
27 * CRC Algorithms for the messaging subsystem. *
28 * *
29 \***************************************************************************/
30 #include "dp_internal.h"
31 #include "dp_bitstream.h"
32 #include "dp_crc.h"
33 using namespace DisplayPort;
34
35 //
36 // DP CRC for transactions headers
37 //
dpCalculateHeaderCRC(BitStreamReader * reader)38 unsigned DisplayPort::dpCalculateHeaderCRC(BitStreamReader * reader)
39 {
40 unsigned remainder = 0;
41 unsigned bit, i;
42
43 while (reader->read(&bit, 1))
44 {
45 remainder <<= 1;
46 remainder |= bit;
47 if ((remainder & 0x10) == 0x10)
48 {
49 remainder ^= 0x13;
50 }
51 }
52
53 for (i = 4; i != 0; i--)
54 {
55 remainder <<= 1;
56 if ((remainder & 0x10) != 0)
57 {
58 remainder ^= 0x13;
59 }
60 }
61
62 return remainder & 0xF;
63 }
64
65 //
66 // DP CRC for body
67 //
dpCalculateBodyCRC(BitStreamReader * reader)68 unsigned DisplayPort::dpCalculateBodyCRC(BitStreamReader * reader)
69 {
70 unsigned remainder = 0;
71 unsigned bit, i;
72
73 while (reader->read(&bit, 1))
74 {
75 remainder <<= 1;
76 remainder |= bit;
77 if ((remainder & 0x100) == 0x100)
78 {
79 remainder ^= 0xD5;
80 }
81 }
82
83 for (i = 8; i != 0; i--)
84 {
85 remainder <<= 1;
86 if ((remainder & 0x100) != 0)
87 {
88 remainder ^= 0xD5;
89 }
90 }
91
92 return remainder & 0xFF;
93 }
94