1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Copyright (c) 2024, The Linux Foundation. All rights reserved.
4 */
5
6#include <linux/types.h>
7
8#include "dp_utils.h"
9
10#define DP_SDP_HEADER_SIZE		8
11
12u8 dp_utils_get_g0_value(u8 data)
13{
14	u8 c[4];
15	u8 g[4];
16	u8 ret_data = 0;
17	u8 i;
18
19	for (i = 0; i < 4; i++)
20		c[i] = (data >> i) & 0x01;
21
22	g[0] = c[3];
23	g[1] = c[0] ^ c[3];
24	g[2] = c[1];
25	g[3] = c[2];
26
27	for (i = 0; i < 4; i++)
28		ret_data = ((g[i] & 0x01) << i) | ret_data;
29
30	return ret_data;
31}
32
33u8 dp_utils_get_g1_value(u8 data)
34{
35	u8 c[4];
36	u8 g[4];
37	u8 ret_data = 0;
38	u8 i;
39
40	for (i = 0; i < 4; i++)
41		c[i] = (data >> i) & 0x01;
42
43	g[0] = c[0] ^ c[3];
44	g[1] = c[0] ^ c[1] ^ c[3];
45	g[2] = c[1] ^ c[2];
46	g[3] = c[2] ^ c[3];
47
48	for (i = 0; i < 4; i++)
49		ret_data = ((g[i] & 0x01) << i) | ret_data;
50
51	return ret_data;
52}
53
54u8 dp_utils_calculate_parity(u32 data)
55{
56	u8 x0 = 0;
57	u8 x1 = 0;
58	u8 ci = 0;
59	u8 iData = 0;
60	u8 i = 0;
61	u8 parity_byte;
62	u8 num_byte = (data & 0xFF00) > 0 ? 8 : 2;
63
64	for (i = 0; i < num_byte; i++) {
65		iData = (data >> i * 4) & 0xF;
66
67		ci = iData ^ x1;
68		x1 = x0 ^ dp_utils_get_g1_value(ci);
69		x0 = dp_utils_get_g0_value(ci);
70	}
71
72	parity_byte = x1 | (x0 << 4);
73
74	return parity_byte;
75}
76
77ssize_t dp_utils_pack_sdp_header(struct dp_sdp_header *sdp_header, u32 *header_buff)
78{
79	size_t length;
80
81	length = sizeof(header_buff);
82	if (length < DP_SDP_HEADER_SIZE)
83		return -ENOSPC;
84
85	header_buff[0] = FIELD_PREP(HEADER_0_MASK, sdp_header->HB0) |
86		FIELD_PREP(PARITY_0_MASK, dp_utils_calculate_parity(sdp_header->HB0)) |
87		FIELD_PREP(HEADER_1_MASK, sdp_header->HB1) |
88		FIELD_PREP(PARITY_1_MASK, dp_utils_calculate_parity(sdp_header->HB1));
89
90	header_buff[1] = FIELD_PREP(HEADER_2_MASK, sdp_header->HB2) |
91		FIELD_PREP(PARITY_2_MASK, dp_utils_calculate_parity(sdp_header->HB2)) |
92		FIELD_PREP(HEADER_3_MASK, sdp_header->HB3) |
93		FIELD_PREP(PARITY_3_MASK, dp_utils_calculate_parity(sdp_header->HB3));
94
95	return length;
96}
97