if (blob_id != 0) {
                new_blob = drm_property_lookup_blob(dev, blob_id);
-               if (new_blob == NULL)
+               if (new_blob == NULL) {
+                       drm_dbg_atomic(dev,
+                                      "cannot find blob ID %llu\n", blob_id);
                        return -EINVAL;
+               }
 
                if (expected_size > 0 &&
                    new_blob->length != expected_size) {
+                       drm_dbg_atomic(dev,
+                                      "[BLOB:%d] length %zu different from expected %zu\n",
+                                      new_blob->base.id, new_blob->length, expected_size);
                        drm_property_blob_put(new_blob);
                        return -EINVAL;
                }
                if (expected_elem_size > 0 &&
                    new_blob->length % expected_elem_size != 0) {
+                       drm_dbg_atomic(dev,
+                                      "[BLOB:%d] length %zu not divisible by element size %zu\n",
+                                      new_blob->base.id, new_blob->length, expected_elem_size);
                        drm_property_blob_put(new_blob);
                        return -EINVAL;
                }