filter.h: Document that the ->close method need not be provided.

diff --git a/filter.h b/filter.h
index 2c1fdac1191516587502833434605fb97bb20339..a11cad50d272981c21d986f6381d3dd41a823c25 100644 (file)
--- a/filter.h
+++ b/filter.h
@@ -64,7 +64,8 @@ struct filter {
         * Close one instance of this filter.
         *
         * Free all resources of associated with \a fn that were previously allocated
-        * by the open() function.
+        * by the open() function. It's OK to leave this alone if the filter does not
+        * need any cleanups.
         */
        void (*close)(struct filter_node *fn);
        /**