drm/edid: add drm_edid helper for drm_edid_to_speaker_allocation()

We'll need to propagate drm_edid everywhere.'

v2: Handle NULL EDID pointer (Ville, CI)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/770d095c93274969c4b86480e07044e16a7b5760.1652097712.git.jani.nikula@intel.com

drivers/gpu/drm/drm_edid.c

@@ -5025,25 +5025,14 @@ int drm_edid_to_sad(const struct edid *edid, struct cea_sad **sads)
 }
 EXPORT_SYMBOL(drm_edid_to_sad);
 
-/**
- * drm_edid_to_speaker_allocation - extracts Speaker Allocation Data Blocks from EDID
- * @edid: EDID to parse
- * @sadb: pointer to the speaker block
- *
- * Looks for CEA EDID block and extracts the Speaker Allocation Data Block from it.
- *
- * Note: The returned pointer needs to be freed using kfree().
- *
- * Return: The number of found Speaker Allocation Blocks or negative number on
- * error.
- */
-int drm_edid_to_speaker_allocation(const struct edid *edid, u8 **sadb)
+static int _drm_edid_to_speaker_allocation(const struct drm_edid *drm_edid,
+					   u8 **sadb)
 {
 	const struct cea_db *db;
 	struct cea_db_iter iter;
 	int count = 0;
 
-	cea_db_iter_edid_begin(edid, &iter);
+	cea_db_iter_edid_begin(drm_edid ? drm_edid->edid : NULL, &iter);
 	cea_db_iter_for_each(db, &iter) {
 		if (cea_db_tag(db) == CTA_DB_SPEAKER &&
 		    cea_db_payload_len(db) == 3) {
@@ -5061,6 +5050,26 @@ int drm_edid_to_speaker_allocation(const struct edid *edid, u8 **sadb)
 
 	return count;
 }
+
+/**
+ * drm_edid_to_speaker_allocation - extracts Speaker Allocation Data Blocks from EDID
+ * @edid: EDID to parse
+ * @sadb: pointer to the speaker block
+ *
+ * Looks for CEA EDID block and extracts the Speaker Allocation Data Block from it.
+ *
+ * Note: The returned pointer needs to be freed using kfree().
+ *
+ * Return: The number of found Speaker Allocation Blocks or negative number on
+ * error.
+ */
+int drm_edid_to_speaker_allocation(const struct edid *edid, u8 **sadb)
+{
+	struct drm_edid drm_edid;
+
+	return _drm_edid_to_speaker_allocation(drm_edid_legacy_init(&drm_edid, edid),
+					       sadb);
+}
 EXPORT_SYMBOL(drm_edid_to_speaker_allocation);
 
 /**