drivers/gpu/drm/drm_displayid.c

Source file repositories/reference/linux-study-clean/drivers/gpu/drm/drm_displayid.c

File Facts

System
Linux kernel
Corpus path
drivers/gpu/drm/drm_displayid.c
Extension
.c
Size
4516 bytes
Lines
205
Domain
Driver Families
Bucket
drivers/gpu
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

struct displayid_quirk {
	const struct drm_edid_ident ident;
	u8 quirks;
};

static const struct displayid_quirk quirks[] = {
	{
		.ident = DRM_EDID_IDENT_INIT('C', 'S', 'O', 5142, "MNE007ZA1-5"),
		.quirks = BIT(QUIRK_IGNORE_CHECKSUM),
	},
};

static u8 get_quirks(const struct drm_edid *drm_edid)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(quirks); i++) {
		if (drm_edid_match(drm_edid, &quirks[i].ident))
			return quirks[i].quirks;
	}

	return 0;
}

static const struct displayid_header *
displayid_get_header(const u8 *displayid, int length, int index)
{
	const struct displayid_header *base;

	if (sizeof(*base) > length - index)
		return ERR_PTR(-EINVAL);

	base = (const struct displayid_header *)&displayid[index];

	return base;
}

static const struct displayid_header *
validate_displayid(const u8 *displayid, int length, int idx, bool ignore_checksum)
{
	int i, dispid_length;
	u8 csum = 0;
	const struct displayid_header *base;

	base = displayid_get_header(displayid, length, idx);
	if (IS_ERR(base))
		return base;

	/* +1 for DispID checksum */
	dispid_length = sizeof(*base) + base->bytes + 1;
	if (dispid_length > length - idx)
		return ERR_PTR(-EINVAL);

	for (i = 0; i < dispid_length; i++)
		csum += displayid[idx + i];
	if (csum) {
		DRM_NOTE("DisplayID checksum invalid, remainder is %d%s\n", csum,
			 ignore_checksum ? " (ignoring)" : "");

		if (!ignore_checksum)
			return ERR_PTR(-EINVAL);
	}

	return base;
}

static const u8 *find_next_displayid_extension(struct displayid_iter *iter)
{
	const struct displayid_header *base;
	const u8 *displayid;
	bool ignore_checksum = iter->quirks & BIT(QUIRK_IGNORE_CHECKSUM);

	displayid = drm_edid_find_extension(iter->drm_edid, DISPLAYID_EXT, &iter->ext_index);
	if (!displayid)
		return NULL;

	/* EDID extensions block checksum isn't for us */
	iter->length = EDID_LENGTH - 1;
	iter->idx = 1;

	base = validate_displayid(displayid, iter->length, iter->idx, ignore_checksum);
	if (IS_ERR(base))
		return NULL;

	iter->length = iter->idx + sizeof(*base) + base->bytes;

	return displayid;
}

void displayid_iter_edid_begin(const struct drm_edid *drm_edid,

Annotation

Implementation Notes