- * If an input module is found, an instance is created and returned.
- * Otherwise, NULL is returned.
+ * If an input module is found, an instance is created into *in.
+ * Otherwise, *in contains NULL.
+ *
+ * If an instance is created, it has the given buffer used for scanning
+ * already submitted to it, to be processed before more data is sent.
+ * This allows a frontend to submit an initial chunk of a non-seekable
+ * stream, such as stdin, without having to keep it around and submit
+ * it again later.