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
12enum {
13 QUIRK_IGNORE_CHECKSUM,
14};
15
16struct displayid_quirk {
17 const struct drm_edid_ident ident;
18 u8 quirks;
19};
20
21static const struct displayid_quirk quirks[] = {
22 {
23 .ident = DRM_EDID_IDENT_INIT('C', 'S', 'O', 5142, "MNE007ZA1-5"),
24 .quirks = BIT(QUIRK_IGNORE_CHECKSUM),
25 },
26};
27
28static u8 get_quirks(const struct drm_edid *drm_edid)
29{
30 int i;
31
32 for (i = 0; i < ARRAY_SIZE(quirks); i++) {
33 if (drm_edid_match(drm_edid, ident: &quirks[i].ident))
34 return quirks[i].quirks;
35 }
36
37 return 0;
38}
39
40static const struct displayid_header *
41displayid_get_header(const u8 *displayid, int length, int index)
42{
43 const struct displayid_header *base;
44
45 if (sizeof(*base) > length - index)
46 return ERR_PTR(error: -EINVAL);
47
48 base = (const struct displayid_header *)&displayid[index];
49
50 return base;
51}
52
53static const struct displayid_header *
54validate_displayid(const u8 *displayid, int length, int idx, bool ignore_checksum)
55{
56 int i, dispid_length;
57 u8 csum = 0;
58 const struct displayid_header *base;
59
60 base = displayid_get_header(displayid, length, index: idx);
61 if (IS_ERR(ptr: base))
62 return base;
63
64 /* +1 for DispID checksum */
65 dispid_length = sizeof(*base) + base->bytes + 1;
66 if (dispid_length > length - idx)
67 return ERR_PTR(error: -EINVAL);
68
69 for (i = 0; i < dispid_length; i++)
70 csum += displayid[idx + i];
71 if (csum) {
72 DRM_NOTE("DisplayID checksum invalid, remainder is %d%s\n", csum,
73 ignore_checksum ? " (ignoring)" : "");
74
75 if (!ignore_checksum)
76 return ERR_PTR(error: -EINVAL);
77 }
78
79 return base;
80}
81
82static const u8 *find_next_displayid_extension(struct displayid_iter *iter)
83{
84 const struct displayid_header *base;
85 const u8 *displayid;
86 bool ignore_checksum = iter->quirks & BIT(QUIRK_IGNORE_CHECKSUM);
87
88 displayid = drm_edid_find_extension(drm_edid: iter->drm_edid, DISPLAYID_EXT, ext_index: &iter->ext_index);
89 if (!displayid)
90 return NULL;
91
92 /* EDID extensions block checksum isn't for us */
93 iter->length = EDID_LENGTH - 1;
94 iter->idx = 1;
95
96 base = validate_displayid(displayid, length: iter->length, idx: iter->idx, ignore_checksum);
97 if (IS_ERR(ptr: base))
98 return NULL;
99
100 iter->length = iter->idx + sizeof(*base) + base->bytes;
101
102 return displayid;
103}
104
105void displayid_iter_edid_begin(const struct drm_edid *drm_edid,
106 struct displayid_iter *iter)
107{
108 memset(iter, 0, sizeof(*iter));
109
110 iter->drm_edid = drm_edid;
111 iter->quirks = get_quirks(drm_edid);
112}
113
114static const struct displayid_block *
115displayid_iter_block(const struct displayid_iter *iter)
116{
117 const struct displayid_block *block;
118
119 if (!iter->section)
120 return NULL;
121
122 block = (const struct displayid_block *)&iter->section[iter->idx];
123
124 if (iter->idx + sizeof(*block) <= iter->length &&
125 iter->idx + sizeof(*block) + block->num_bytes <= iter->length)
126 return block;
127
128 return NULL;
129}
130
131const struct displayid_block *
132__displayid_iter_next(struct displayid_iter *iter)
133{
134 const struct displayid_block *block;
135
136 if (!iter->drm_edid)
137 return NULL;
138
139 if (iter->section) {
140 /* current block should always be valid */
141 block = displayid_iter_block(iter);
142 if (WARN_ON(!block)) {
143 iter->section = NULL;
144 iter->drm_edid = NULL;
145 return NULL;
146 }
147
148 /* next block in section */
149 iter->idx += sizeof(*block) + block->num_bytes;
150
151 block = displayid_iter_block(iter);
152 if (block)
153 return block;
154 }
155
156 for (;;) {
157 /* The first section we encounter is the base section */
158 bool base_section = !iter->section;
159
160 iter->section = find_next_displayid_extension(iter);
161 if (!iter->section) {
162 iter->drm_edid = NULL;
163 return NULL;
164 }
165
166 /* Save the structure version and primary use case. */
167 if (base_section) {
168 const struct displayid_header *base;
169
170 base = displayid_get_header(displayid: iter->section, length: iter->length,
171 index: iter->idx);
172 if (!IS_ERR(ptr: base)) {
173 iter->version = base->rev;
174 iter->primary_use = base->prod_id;
175 }
176 }
177
178 iter->idx += sizeof(struct displayid_header);
179
180 block = displayid_iter_block(iter);
181 if (block)
182 return block;
183 }
184}
185
186void displayid_iter_end(struct displayid_iter *iter)
187{
188 memset(iter, 0, sizeof(*iter));
189}
190
191/* DisplayID Structure Version/Revision from the Base Section. */
192u8 displayid_version(const struct displayid_iter *iter)
193{
194 return iter->version;
195}
196
197/*
198 * DisplayID Primary Use Case (2.0+) or Product Type Identifier (1.0-1.3) from
199 * the Base Section.
200 */
201u8 displayid_primary_use(const struct displayid_iter *iter)
202{
203 return iter->primary_use;
204}
205

source code of linux/drivers/gpu/drm/drm_displayid.c