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
10static const struct displayid_header *
11displayid_get_header(const u8 *displayid, int length, int index)
12{
13	const struct displayid_header *base;
14
15	if (sizeof(*base) > length - index)
16		return ERR_PTR(-EINVAL);
17
18	base = (const struct displayid_header *)&displayid[index];
19
20	return base;
21}
22
23static const struct displayid_header *
24validate_displayid(const u8 *displayid, int length, int idx)
25{
26	int i, dispid_length;
27	u8 csum = 0;
28	const struct displayid_header *base;
29
30	base = displayid_get_header(displayid, length, idx);
31	if (IS_ERR(base))
32		return base;
33
34	DRM_DEBUG_KMS("base revision 0x%x, length %d, %d %d\n",
35		      base->rev, base->bytes, base->prod_id, base->ext_count);
36
37	/* +1 for DispID checksum */
38	dispid_length = sizeof(*base) + base->bytes + 1;
39	if (dispid_length > length - idx)
40		return ERR_PTR(-EINVAL);
41
42	for (i = 0; i < dispid_length; i++)
43		csum += displayid[idx + i];
44	if (csum) {
45		DRM_NOTE("DisplayID checksum invalid, remainder is %d\n", csum);
46		return ERR_PTR(-EINVAL);
47	}
48
49	return base;
50}
51
52static const u8 *drm_find_displayid_extension(const struct drm_edid *drm_edid,
53					      int *length, int *idx,
54					      int *ext_index)
55{
56	const u8 *displayid = drm_find_edid_extension(drm_edid, DISPLAYID_EXT, ext_index);
57	const struct displayid_header *base;
58
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
75void 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
83static const struct displayid_block *
84displayid_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
100const struct displayid_block *
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
158void 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. */
164u8 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 */
173u8 displayid_primary_use(const struct displayid_iter *iter)
174{
175	return iter->primary_use;
176}
177