1 // SPDX-License-Identifier: MIT
2 /*
3 * Copyright © 2021 Intel Corporation
4 */
5
6 #include <drm/drm_displayid.h>
7 #include <drm/drm_edid.h>
8 #include <drm/drm_print.h>
9
validate_displayid(const u8 * displayid,int length,int idx)10 static int validate_displayid(const u8 *displayid, int length, int idx)
11 {
12 int i, dispid_length;
13 u8 csum = 0;
14 const struct displayid_header *base;
15
16 base = (const struct displayid_header *)&displayid[idx];
17
18 DRM_DEBUG_KMS("base revision 0x%x, length %d, %d %d\n",
19 base->rev, base->bytes, base->prod_id, base->ext_count);
20
21 /* +1 for DispID checksum */
22 dispid_length = sizeof(*base) + base->bytes + 1;
23 if (dispid_length > length - idx)
24 return -EINVAL;
25
26 for (i = 0; i < dispid_length; i++)
27 csum += displayid[idx + i];
28 if (csum) {
29 DRM_NOTE("DisplayID checksum invalid, remainder is %d\n", csum);
30 return -EINVAL;
31 }
32
33 return 0;
34 }
35
drm_find_displayid_extension(const struct edid * edid,int * length,int * idx,int * ext_index)36 static const u8 *drm_find_displayid_extension(const struct edid *edid,
37 int *length, int *idx,
38 int *ext_index)
39 {
40 const u8 *displayid = drm_find_edid_extension(edid, DISPLAYID_EXT, ext_index);
41 const struct displayid_header *base;
42 int ret;
43
44 if (!displayid)
45 return NULL;
46
47 /* EDID extensions block checksum isn't for us */
48 *length = EDID_LENGTH - 1;
49 *idx = 1;
50
51 ret = validate_displayid(displayid, *length, *idx);
52 if (ret)
53 return NULL;
54
55 base = (const struct displayid_header *)&displayid[*idx];
56 *length = *idx + sizeof(*base) + base->bytes;
57
58 return displayid;
59 }
60
displayid_iter_edid_begin(const struct edid * edid,struct displayid_iter * iter)61 void displayid_iter_edid_begin(const struct edid *edid,
62 struct displayid_iter *iter)
63 {
64 memset(iter, 0, sizeof(*iter));
65
66 iter->edid = edid;
67 }
68
69 static const struct displayid_block *
displayid_iter_block(const struct displayid_iter * iter)70 displayid_iter_block(const struct displayid_iter *iter)
71 {
72 const struct displayid_block *block;
73
74 if (!iter->section)
75 return NULL;
76
77 block = (const struct displayid_block *)&iter->section[iter->idx];
78
79 if (iter->idx + sizeof(*block) <= iter->length &&
80 iter->idx + sizeof(*block) + block->num_bytes <= iter->length)
81 return block;
82
83 return NULL;
84 }
85
86 const struct displayid_block *
__displayid_iter_next(struct displayid_iter * iter)87 __displayid_iter_next(struct displayid_iter *iter)
88 {
89 const struct displayid_block *block;
90
91 if (!iter->edid)
92 return NULL;
93
94 if (iter->section) {
95 /* current block should always be valid */
96 block = displayid_iter_block(iter);
97 if (WARN_ON(!block)) {
98 iter->section = NULL;
99 iter->edid = NULL;
100 return NULL;
101 }
102
103 /* next block in section */
104 iter->idx += sizeof(*block) + block->num_bytes;
105
106 block = displayid_iter_block(iter);
107 if (block)
108 return block;
109 }
110
111 for (;;) {
112 iter->section = drm_find_displayid_extension(iter->edid,
113 &iter->length,
114 &iter->idx,
115 &iter->ext_index);
116 if (!iter->section) {
117 iter->edid = NULL;
118 return NULL;
119 }
120
121 iter->idx += sizeof(struct displayid_header);
122
123 block = displayid_iter_block(iter);
124 if (block)
125 return block;
126 }
127 }
128
displayid_iter_end(struct displayid_iter * iter)129 void displayid_iter_end(struct displayid_iter *iter)
130 {
131 memset(iter, 0, sizeof(*iter));
132 }
133