1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * cec-edid - HDMI Consumer Electronics Control EDID & CEC helper functions
4 *
5 * Copyright 2016 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
6 */
7
8 #include <linux/module.h>
9 #include <linux/kernel.h>
10 #include <linux/types.h>
11 #include <media/cec.h>
12
13 /*
14 * This EDID is expected to be a CEA-861 compliant, which means that there are
15 * at least two blocks and one or more of the extensions blocks are CEA-861
16 * blocks.
17 *
18 * The returned location is guaranteed to be < size - 1.
19 */
cec_get_edid_spa_location(const u8 * edid,unsigned int size)20 static unsigned int cec_get_edid_spa_location(const u8 *edid, unsigned int size)
21 {
22 unsigned int blocks = size / 128;
23 unsigned int block;
24 u8 d;
25
26 /* Sanity check: at least 2 blocks and a multiple of the block size */
27 if (blocks < 2 || size % 128)
28 return 0;
29
30 /*
31 * If there are fewer extension blocks than the size, then update
32 * 'blocks'. It is allowed to have more extension blocks than the size,
33 * since some hardware can only read e.g. 256 bytes of the EDID, even
34 * though more blocks are present. The first CEA-861 extension block
35 * should normally be in block 1 anyway.
36 */
37 if (edid[0x7e] + 1 < blocks)
38 blocks = edid[0x7e] + 1;
39
40 for (block = 1; block < blocks; block++) {
41 unsigned int offset = block * 128;
42
43 /* Skip any non-CEA-861 extension blocks */
44 if (edid[offset] != 0x02 || edid[offset + 1] != 0x03)
45 continue;
46
47 /* search Vendor Specific Data Block (tag 3) */
48 d = edid[offset + 2] & 0x7f;
49 /* Check if there are Data Blocks */
50 if (d <= 4)
51 continue;
52 if (d > 4) {
53 unsigned int i = offset + 4;
54 unsigned int end = offset + d;
55
56 /* Note: 'end' is always < 'size' */
57 do {
58 u8 tag = edid[i] >> 5;
59 u8 len = edid[i] & 0x1f;
60
61 if (tag == 3 && len >= 5 && i + len <= end &&
62 edid[i + 1] == 0x03 &&
63 edid[i + 2] == 0x0c &&
64 edid[i + 3] == 0x00)
65 return i + 4;
66 i += len + 1;
67 } while (i < end);
68 }
69 }
70 return 0;
71 }
72
cec_get_edid_phys_addr(const u8 * edid,unsigned int size,unsigned int * offset)73 u16 cec_get_edid_phys_addr(const u8 *edid, unsigned int size,
74 unsigned int *offset)
75 {
76 unsigned int loc = cec_get_edid_spa_location(edid, size);
77
78 if (offset)
79 *offset = loc;
80 if (loc == 0)
81 return CEC_PHYS_ADDR_INVALID;
82 return (edid[loc] << 8) | edid[loc + 1];
83 }
84 EXPORT_SYMBOL_GPL(cec_get_edid_phys_addr);
85
cec_set_edid_phys_addr(u8 * edid,unsigned int size,u16 phys_addr)86 void cec_set_edid_phys_addr(u8 *edid, unsigned int size, u16 phys_addr)
87 {
88 unsigned int loc = cec_get_edid_spa_location(edid, size);
89 u8 sum = 0;
90 unsigned int i;
91
92 if (loc == 0)
93 return;
94 edid[loc] = phys_addr >> 8;
95 edid[loc + 1] = phys_addr & 0xff;
96 loc &= ~0x7f;
97
98 /* update the checksum */
99 for (i = loc; i < loc + 127; i++)
100 sum += edid[i];
101 edid[i] = 256 - sum;
102 }
103 EXPORT_SYMBOL_GPL(cec_set_edid_phys_addr);
104
cec_phys_addr_for_input(u16 phys_addr,u8 input)105 u16 cec_phys_addr_for_input(u16 phys_addr, u8 input)
106 {
107 /* Check if input is sane */
108 if (WARN_ON(input == 0 || input > 0xf))
109 return CEC_PHYS_ADDR_INVALID;
110
111 if (phys_addr == 0)
112 return input << 12;
113
114 if ((phys_addr & 0x0fff) == 0)
115 return phys_addr | (input << 8);
116
117 if ((phys_addr & 0x00ff) == 0)
118 return phys_addr | (input << 4);
119
120 if ((phys_addr & 0x000f) == 0)
121 return phys_addr | input;
122
123 /*
124 * All nibbles are used so no valid physical addresses can be assigned
125 * to the input.
126 */
127 return CEC_PHYS_ADDR_INVALID;
128 }
129 EXPORT_SYMBOL_GPL(cec_phys_addr_for_input);
130
cec_phys_addr_validate(u16 phys_addr,u16 * parent,u16 * port)131 int cec_phys_addr_validate(u16 phys_addr, u16 *parent, u16 *port)
132 {
133 int i;
134
135 if (parent)
136 *parent = phys_addr;
137 if (port)
138 *port = 0;
139 if (phys_addr == CEC_PHYS_ADDR_INVALID)
140 return 0;
141 for (i = 0; i < 16; i += 4)
142 if (phys_addr & (0xf << i))
143 break;
144 if (i == 16)
145 return 0;
146 if (parent)
147 *parent = phys_addr & (0xfff0 << i);
148 if (port)
149 *port = (phys_addr >> i) & 0xf;
150 for (i += 4; i < 16; i += 4)
151 if ((phys_addr & (0xf << i)) == 0)
152 return -EINVAL;
153 return 0;
154 }
155 EXPORT_SYMBOL_GPL(cec_phys_addr_validate);
156
