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
 12static const struct displayid_header *
 13displayid_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
 25static const struct displayid_header *
 26validate_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
 51static 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
 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}