Commit aba58254 authored by Jani Nikula's avatar Jani Nikula
Browse files

drm/edid: add iterator for CTA data blocks 



Add an iterator for CTA Data Blocks across EDID CTA Extensions and
DisplayID CTA Data Blocks.

v2: Update references, note why we can trust displayid ranges (Ville)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
Reviewed-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/37fdd2d9eabc73aaa9f95c56246dc47aea0e8e4e.1651569697.git.jani.nikula@intel.com
parent 94afc538

drivers/gpu/drm/drm_edid.c

+190 −12
Original line number Diff line number Diff line
@@ -4336,24 +4336,12 @@ do_hdmi_vsdb_modes(struct drm_connector *connector, const u8 *db, u8 len, 
	return modes;

}



static int

cea_db_payload_len(const u8 *db)

{

	return db[0] & 0x1f;

}



static int

cea_db_extended_tag(const u8 *db)

{

	return db[1];

}



static int

cea_db_tag(const u8 *db)

{

	return db[0] >> 5;

}



static int

cea_revision(const u8 *cea)

{
@@ -4409,6 +4397,196 @@ cea_db_offsets(const u8 *cea, int *start, int *end) 
	return 0;

}



/*

 * CTA Data Block iterator.

 *

 * Iterate through all CTA Data Blocks in both EDID CTA Extensions and DisplayID

 * CTA Data Blocks.

 *

 * struct cea_db *db:

 * struct cea_db_iter iter;

 *

 * cea_db_iter_edid_begin(edid, &iter);

 * cea_db_iter_for_each(db, &iter) {

 *         // do stuff with db

 * }

 * cea_db_iter_end(&iter);

 */

struct cea_db_iter {

	struct drm_edid_iter edid_iter;

	struct displayid_iter displayid_iter;



	/* Current Data Block Collection. */

	const u8 *collection;



	/* Current Data Block index in current collection. */

	int index;



	/* End index in current collection. */

	int end;

};



/* CTA-861-H section 7.4 CTA Data BLock Collection */

struct cea_db {

	u8 tag_length;

	u8 data[];

} __packed;



static int cea_db_tag(const void *_db)

{

	/* FIXME: Transition to passing struct cea_db * everywhere. */

	const struct cea_db *db = _db;



	return db->tag_length >> 5;

}



static int cea_db_payload_len(const void *_db)

{

	/* FIXME: Transition to passing struct cea_db * everywhere. */

	const struct cea_db *db = _db;



	return db->tag_length & 0x1f;

}



static const void *cea_db_data(const struct cea_db *db)

{

	return db->data;

}



static void cea_db_iter_edid_begin(const struct edid *edid, struct cea_db_iter *iter)

{

	memset(iter, 0, sizeof(*iter));



	drm_edid_iter_begin(edid, &iter->edid_iter);

	displayid_iter_edid_begin(edid, &iter->displayid_iter);

}



static const struct cea_db *

__cea_db_iter_current_block(const struct cea_db_iter *iter)

{

	const struct cea_db *db;



	if (!iter->collection)

		return NULL;



	db = (const struct cea_db *)&iter->collection[iter->index];



	if (iter->index + sizeof(*db) <= iter->end &&

	    iter->index + sizeof(*db) + cea_db_payload_len(db) <= iter->end)

		return db;



	return NULL;

}



/*

 * References:

 * - VESA E-EDID v1.4

 * - CTA-861-H section 7.3.3 CTA Extension Version 3

 */

static const void *__cea_db_iter_edid_next(struct cea_db_iter *iter)

{

	const u8 *ext;



	drm_edid_iter_for_each(ext, &iter->edid_iter) {

		/* Only support CTA Extension revision 3+ */

		if (ext[0] != CEA_EXT || cea_revision(ext) < 3)

			continue;



		iter->index = 4;

		iter->end = ext[2];

		if (iter->end == 0)

			iter->end = 127;

		if (iter->end < 4 || iter->end > 127)

			continue;



		return ext;

	}



	return NULL;

}



/*

 * References:

 * - DisplayID v1.3 Appendix C: CEA Data Block within a DisplayID Data Block

 * - DisplayID v2.0 section 4.10 CTA DisplayID Data Block

 *

 * Note that the above do not specify any connection between DisplayID Data

 * Block revision and CTA Extension versions.

 */

static const void *__cea_db_iter_displayid_next(struct cea_db_iter *iter)

{

	const struct displayid_block *block;



	displayid_iter_for_each(block, &iter->displayid_iter) {

		if (block->tag != DATA_BLOCK_CTA)

			continue;



		/*

		 * The displayid iterator has already verified the block bounds

		 * in displayid_iter_block().

		 */

		iter->index = sizeof(*block);

		iter->end = iter->index + block->num_bytes;



		return block;

	}



	return NULL;

}



static const struct cea_db *__cea_db_iter_next(struct cea_db_iter *iter)

{

	const struct cea_db *db;



	if (iter->collection) {

		/* Current collection should always be valid. */

		db = __cea_db_iter_current_block(iter);

		if (WARN_ON(!db)) {

			iter->collection = NULL;

			return NULL;

		}



		/* Next block in CTA Data Block Collection */

		iter->index += sizeof(*db) + cea_db_payload_len(db);



		db = __cea_db_iter_current_block(iter);

		if (db)

			return db;

	}



	for (;;) {

		/*

		 * Find the next CTA Data Block Collection. First iterate all

		 * the EDID CTA Extensions, then all the DisplayID CTA blocks.

		 *

		 * Per DisplayID v1.3 Appendix B: DisplayID as an EDID

		 * Extension, it's recommended that DisplayID extensions are

		 * exposed after all of the CTA Extensions.

		 */

		iter->collection = __cea_db_iter_edid_next(iter);

		if (!iter->collection)

			iter->collection = __cea_db_iter_displayid_next(iter);



		if (!iter->collection)

			return NULL;



		db = __cea_db_iter_current_block(iter);

		if (db)

			return db;

	}

}



#define cea_db_iter_for_each(__db, __iter) \

	while (((__db) = __cea_db_iter_next(__iter)))



static void cea_db_iter_end(struct cea_db_iter *iter)

{

	displayid_iter_end(&iter->displayid_iter);

	drm_edid_iter_end(&iter->edid_iter);



	memset(iter, 0, sizeof(*iter));

}



static bool cea_db_is_hdmi_vsdb(const u8 *db)

{

	if (cea_db_tag(db) != CTA_DB_VENDOR)