1 // SPDX-License-Identifier: MIT
2 /*
3 * Copyright © 2021 Intel Corporation
4 */
5
6 #include <drm/drm_edid.h>
7 #include <drm/drm_print.h>
8
9 #include "drm_crtc_internal.h"
10 #include "drm_displayid_internal.h"
11
12 static const struct displayid_header *
displayid_get_header(const u8 * displayid,int length,int index)13 displayid_get_header(const u8 *displayid, int length, int index)
14 {
15 const struct displayid_header *base;
16
17 if (sizeof(*base) > length - index)
18 return ERR_PTR(-EINVAL);
19
20 base = (const struct displayid_header *)&displayid[index];
21
22 return base;
23 }
24
25 static const struct displayid_header *
validate_displayid(const u8 * displayid,int length,int idx)26 validate_displayid(const u8 *displayid, int length, int idx)
27 {
28 int i, dispid_length;
29 u8 csum = 0;
30 const struct displayid_header *base;
31
32 base = displayid_get_header(displayid, length, idx);
33 if (IS_ERR(base))
34 return base;
35
36 /* +1 for DispID checksum */
37 dispid_length = sizeof(*base) + base->bytes + 1;
38 if (dispid_length > length - idx)
39 return ERR_PTR(-EINVAL);
40
41 for (i = 0; i < dispid_length; i++)
42 csum += displayid[idx + i];
43 if (csum) {
44 DRM_NOTE("DisplayID checksum invalid, remainder is %d\n", csum);
45 return ERR_PTR(-EINVAL);
46 }
47
48 return base;
49 }
50
drm_find_displayid_extension(const struct drm_edid * drm_edid,int * length,int * idx,int * ext_index)51 static const u8 *drm_find_displayid_extension(const struct drm_edid *drm_edid,
52 int *length, int *idx,
53 int *ext_index)
54 {
55 const struct displayid_header *base;
56 const u8 *displayid;
57
58 displayid = drm_edid_find_extension(drm_edid, DISPLAYID_EXT, ext_index);
59 if (!displayid)
60 return NULL;
61
62 /* EDID extensions block checksum isn't for us */
63 *length = EDID_LENGTH - 1;
64 *idx = 1;
65
66 base = validate_displayid(displayid, *length, *idx);
67 if (IS_ERR(base))
68 return NULL;
69
70 *length = *idx + sizeof(*base) + base->bytes;
71
72 return displayid;
73 }
74
displayid_iter_edid_begin(const struct drm_edid * drm_edid,struct displayid_iter * iter)75 void displayid_iter_edid_begin(const struct drm_edid *drm_edid,
76 struct displayid_iter *iter)
77 {
78 memset(iter, 0, sizeof(*iter));
79
80 iter->drm_edid = drm_edid;
81 }
82
83 static const struct displayid_block *
displayid_iter_block(const struct displayid_iter * iter)84 displayid_iter_block(const struct displayid_iter *iter)
85 {
86 const struct displayid_block *block;
87
88 if (!iter->section)
89 return NULL;
90
91 block = (const struct displayid_block *)&iter->section[iter->idx];
92
93 if (iter->idx + sizeof(*block) <= iter->length &&
94 iter->idx + sizeof(*block) + block->num_bytes <= iter->length)
95 return block;
96
97 return NULL;
98 }
99
100 const struct displayid_block *
__displayid_iter_next(struct displayid_iter * iter)101 __displayid_iter_next(struct displayid_iter *iter)
102 {
103 const struct displayid_block *block;
104
105 if (!iter->drm_edid)
106 return NULL;
107
108 if (iter->section) {
109 /* current block should always be valid */
110 block = displayid_iter_block(iter);
111 if (WARN_ON(!block)) {
112 iter->section = NULL;
113 iter->drm_edid = NULL;
114 return NULL;
115 }
116
117 /* next block in section */
118 iter->idx += sizeof(*block) + block->num_bytes;
119
120 block = displayid_iter_block(iter);
121 if (block)
122 return block;
123 }
124
125 for (;;) {
126 /* The first section we encounter is the base section */
127 bool base_section = !iter->section;
128
129 iter->section = drm_find_displayid_extension(iter->drm_edid,
130 &iter->length,
131 &iter->idx,
132 &iter->ext_index);
133 if (!iter->section) {
134 iter->drm_edid = NULL;
135 return NULL;
136 }
137
138 /* Save the structure version and primary use case. */
139 if (base_section) {
140 const struct displayid_header *base;
141
142 base = displayid_get_header(iter->section, iter->length,
143 iter->idx);
144 if (!IS_ERR(base)) {
145 iter->version = base->rev;
146 iter->primary_use = base->prod_id;
147 }
148 }
149
150 iter->idx += sizeof(struct displayid_header);
151
152 block = displayid_iter_block(iter);
153 if (block)
154 return block;
155 }
156 }
157
displayid_iter_end(struct displayid_iter * iter)158 void displayid_iter_end(struct displayid_iter *iter)
159 {
160 memset(iter, 0, sizeof(*iter));
161 }
162
163 /* DisplayID Structure Version/Revision from the Base Section. */
displayid_version(const struct displayid_iter * iter)164 u8 displayid_version(const struct displayid_iter *iter)
165 {
166 return iter->version;
167 }
168
169 /*
170 * DisplayID Primary Use Case (2.0+) or Product Type Identifier (1.0-1.3) from
171 * the Base Section.
172 */
displayid_primary_use(const struct displayid_iter * iter)173 u8 displayid_primary_use(const struct displayid_iter *iter)
174 {
175 return iter->primary_use;
176 }
177