drm/edid: clean up cea_db_is_*() functions

Abstract helpers for matching vendor data blocks and extended tags, and
use them to simplify all the cea_db_is_*() functions.

Take void pointer as parameter to allow transitional use for both u8 *
and struct cea_db *.

v2: Remove superfluous parens (Ville)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/b6bb813afc35c763e744c6cdb4a787da3adf910b.1651569697.git.jani.nikula@intel.com

drivers/gpu/drm/drm_edid.c

@@ -4336,12 +4336,6 @@ do_hdmi_vsdb_modes(struct drm_connector *connector, const u8 *db, u8 len,
 	return modes;
 }
 
-static int
-cea_db_extended_tag(const u8 *db)
-{
-	return db[1];
-}
-
 static int
 cea_revision(const u8 *cea)
 {
@@ -4453,6 +4447,22 @@ static const void *cea_db_data(const struct cea_db *db)
 	return db->data;
 }
 
+static bool cea_db_is_extended_tag(const struct cea_db *db, int tag)
+{
+	return cea_db_tag(db) == CTA_DB_EXTENDED_TAG &&
+		cea_db_payload_len(db) >= 1 &&
+		db->data[0] == tag;
+}
+
+static bool cea_db_is_vendor(const struct cea_db *db, int vendor_oui)
+{
+	const u8 *data = cea_db_data(db);
+
+	return cea_db_tag(db) == CTA_DB_VENDOR &&
+		cea_db_payload_len(db) >= 3 &&
+		oui(data[2], data[1], data[0]) == vendor_oui;
+}
+
 static void cea_db_iter_edid_begin(const struct edid *edid, struct cea_db_iter *iter)
 {
 	memset(iter, 0, sizeof(*iter));
@@ -4587,93 +4597,50 @@ static void cea_db_iter_end(struct cea_db_iter *iter)
 	memset(iter, 0, sizeof(*iter));
 }
 
-static bool cea_db_is_hdmi_vsdb(const u8 *db)
+static bool cea_db_is_hdmi_vsdb(const void *db)
 {
-	if (cea_db_tag(db) != CTA_DB_VENDOR)
-		return false;
-
-	if (cea_db_payload_len(db) < 5)
-		return false;
-
-	return oui(db[3], db[2], db[1]) == HDMI_IEEE_OUI;
+	return cea_db_is_vendor(db, HDMI_IEEE_OUI) &&
+		cea_db_payload_len(db) >= 5;
 }
 
-static bool cea_db_is_hdmi_forum_vsdb(const u8 *db)
+static bool cea_db_is_hdmi_forum_vsdb(const void *db)
 {
-	if (cea_db_tag(db) != CTA_DB_VENDOR)
-		return false;
-
-	if (cea_db_payload_len(db) < 7)
-		return false;
-
-	return oui(db[3], db[2], db[1]) == HDMI_FORUM_IEEE_OUI;
+	return cea_db_is_vendor(db, HDMI_FORUM_IEEE_OUI) &&
+		cea_db_payload_len(db) >= 7;
 }
 
-static bool cea_db_is_microsoft_vsdb(const u8 *db)
+static bool cea_db_is_microsoft_vsdb(const void *db)
 {
-	if (cea_db_tag(db) != CTA_DB_VENDOR)
-		return false;
-
-	if (cea_db_payload_len(db) != 21)
-		return false;
-
-	return oui(db[3], db[2], db[1]) == MICROSOFT_IEEE_OUI;
+	return cea_db_is_vendor(db, MICROSOFT_IEEE_OUI) &&
+		cea_db_payload_len(db) == 21;
 }
 
-static bool cea_db_is_vcdb(const u8 *db)
+static bool cea_db_is_vcdb(const void *db)
 {
-	if (cea_db_tag(db) != CTA_DB_EXTENDED_TAG)
-		return false;
-
-	if (cea_db_payload_len(db) != 2)
-		return false;
-
-	if (cea_db_extended_tag(db) != CTA_EXT_DB_VIDEO_CAP)
-		return false;
-
-	return true;
+	return cea_db_is_extended_tag(db, CTA_EXT_DB_VIDEO_CAP) &&
+		cea_db_payload_len(db) == 2;
 }
 
-static bool cea_db_is_hdmi_forum_scdb(const u8 *db)
+static bool cea_db_is_hdmi_forum_scdb(const void *db)
 {
-	if (cea_db_tag(db) != CTA_DB_EXTENDED_TAG)
-		return false;
-
-	if (cea_db_payload_len(db) < 7)
-		return false;
-
-	if (cea_db_extended_tag(db) != CTA_EXT_DB_HF_SCDB)
-		return false;
-
-	return true;
+	return cea_db_is_extended_tag(db, CTA_EXT_DB_HF_SCDB) &&
+		cea_db_payload_len(db) >= 7;
 }
 
-static bool cea_db_is_y420cmdb(const u8 *db)
+static bool cea_db_is_y420cmdb(const void *db)
 {
-	if (cea_db_tag(db) != CTA_DB_EXTENDED_TAG)
-		return false;
-
-	if (!cea_db_payload_len(db))
-		return false;
-
-	if (cea_db_extended_tag(db) != CTA_EXT_DB_420_VIDEO_CAP_MAP)
-		return false;
-
-	return true;
+	return cea_db_is_extended_tag(db, CTA_EXT_DB_420_VIDEO_CAP_MAP);
 }
 
-static bool cea_db_is_y420vdb(const u8 *db)
+static bool cea_db_is_y420vdb(const void *db)
 {
-	if (cea_db_tag(db) != CTA_DB_EXTENDED_TAG)
-		return false;
-
-	if (!cea_db_payload_len(db))
-		return false;
-
-	if (cea_db_extended_tag(db) != CTA_EXT_DB_420_VIDEO_DATA)
-		return false;
+	return cea_db_is_extended_tag(db, CTA_EXT_DB_420_VIDEO_DATA);
+}
 
-	return true;
+static bool cea_db_is_hdmi_hdr_metadata_block(const void *db)
+{
+	return cea_db_is_extended_tag(db, CTA_EXT_DB_HDR_STATIC_METADATA) &&
+		cea_db_payload_len(db) >= 3;
 }
 
 #define for_each_cea_db(cea, i, start, end) \
@@ -4809,20 +4776,6 @@ static void fixup_detailed_cea_mode_clock(struct drm_display_mode *mode)
 	mode->clock = clock;
 }
 
-static bool cea_db_is_hdmi_hdr_metadata_block(const u8 *db)
-{
-	if (cea_db_tag(db) != CTA_DB_EXTENDED_TAG)
-		return false;
-
-	if (db[1] != CTA_EXT_DB_HDR_STATIC_METADATA)
-		return false;
-
-	if (cea_db_payload_len(db) < 3)
-		return false;
-
-	return true;
-}
-
 static uint8_t eotf_supported(const u8 *edid_ext)
 {
 	return edid_ext[2] &