drm/edid: make drm_edid_are_equal() more convenient for its single user

Repurpose drm_edid_are_equal() to be more helpful for its single user,
and rename drm_edid_eq(). Functionally deduce the length from the blob
size, not the blob data, making it more robust against any errors.
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/1011a285d30babce3aabd8218abb7ece7dcf58a2.1713259151.git.jani.nikula@intel.comSigned-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/drm_edid.c

@@ -1820,30 +1820,20 @@ static bool edid_block_is_zero(const void *edid)
 	return !memchr_inv(edid, 0, EDID_LENGTH);
 }
 
-/**
- * drm_edid_are_equal - compare two edid blobs.
- * @edid1: pointer to first blob
- * @edid2: pointer to second blob
- * This helper can be used during probing to determine if
- * edid had changed.
- */
-static bool drm_edid_are_equal(const struct edid *edid1, const struct edid *edid2)
+static bool drm_edid_eq(const struct drm_edid *drm_edid,
+			const void *raw_edid, size_t raw_edid_size)
 {
-	int edid1_len, edid2_len;
-	bool edid1_present = edid1 != NULL;
-	bool edid2_present = edid2 != NULL;
+	bool edid1_present = drm_edid && drm_edid->edid && drm_edid->size;
+	bool edid2_present = raw_edid && raw_edid_size;
 
 	if (edid1_present != edid2_present)
 		return false;
 
-	if (edid1) {
-		edid1_len = edid_size(edid1);
-		edid2_len = edid_size(edid2);
-
-		if (edid1_len != edid2_len)
+	if (edid1_present) {
+		if (drm_edid->size != raw_edid_size)
 			return false;
 
-		if (memcmp(edid1, edid2, edid1_len))
+		if (memcmp(drm_edid->edid, raw_edid, drm_edid->size))
 			return false;
 	}
 
@@ -6936,15 +6926,14 @@ static int _drm_edid_connector_property_update(struct drm_connector *connector,
 	int ret;
 
 	if (connector->edid_blob_ptr) {
-		const struct edid *old_edid = connector->edid_blob_ptr->data;
-
-		if (old_edid) {
-			if (!drm_edid_are_equal(drm_edid ? drm_edid->edid : NULL, old_edid)) {
-				connector->epoch_counter++;
-				drm_dbg_kms(dev, "[CONNECTOR:%d:%s] EDID changed, epoch counter %llu\n",
-					    connector->base.id, connector->name,
-					    connector->epoch_counter);
-			}
+		const void *old_edid = connector->edid_blob_ptr->data;
+		size_t old_edid_size = connector->edid_blob_ptr->length;
+
+		if (old_edid && !drm_edid_eq(drm_edid, old_edid, old_edid_size)) {
+			connector->epoch_counter++;
+			drm_dbg_kms(dev, "[CONNECTOR:%d:%s] EDID changed, epoch counter %llu\n",
+				    connector->base.id, connector->name,
+				    connector->epoch_counter);
 		}
 	}