/**
* Open one instance of this filter.
*
- * This should allocate the output buffer of the given filter node and do any
- * other filter-specific preparations like initializing the private_data member
- * of \a fn suitably. The open function is assumed to succeed.
+ * This should allocate the output buffer of the given filter node and
+ * do any other filter-specific preparations like initializing the
+ * private_data member of \a fn suitably. The open function is
+ * optional, If it is provided, it is assumed to succeed.
*/
void (*open)(struct filter_node *fn);
/**
* Close one instance of this filter.
*
- * Free all resources of associated with \a fn that were previously allocated
- * by the open() function. It's OK to leave this alone if the filter does not
- * need any cleanups.
+ * Free all resources associated with \a fn that were previously
+ * allocated by the open() function. It's OK to set this to NULL if the
+ * filter does not need to perform any cleanup operation.
*/
void (*close)(struct filter_node *fn);
/**