filter.h: Add some missing documentation.

diff --git a/filter.h b/filter.h
index befcd3381abd539ec743bf3e28b5198d7b093b50..c34acca8e96063804fd0d4cf788ac27658ca94b7 100644 (file)
--- a/filter.h
+++ b/filter.h
@@ -81,19 +81,38 @@ struct filter {
         * argv. On failure, a negative paraslash error code must be returned.
         */
        int (*parse_config)(int argc, char **argv, void **config);
+       /**
+        * Deallocate the memory for the configuration.
+        *
+        * This is called to free whatever ->parse_config() has allocated.
+        */
        void (*free_config)(void *conf);
 
        /** The help texts for this filter. */
        struct ggo_help help;
+       /**
+        * Set scheduler timeout and add file descriptors to fd sets.
+        *
+        * This function is used to control the timeout value for select. It
+        * only allowed to decrease the current value. The second purpose of
+        * this function is to set file descriptors to be watched by the
+        * subsequent select call to the two fd sets.
+        */
        void (*pre_select)(struct sched *s, struct task *t);
        /**
         * Convert (filter) the given data.
         *
-        * Pointer to the converting function of the filter. It should convert as
-        * input data as possible. On errors, the post_select function is supposed
-        * to set t->error to a (negative) error code.
+        * Pointer to the converting function of the filter. On errors, the
+        * post_select function is supposed to set t->error to a (negative)
+        * error code.
         */
        void (*post_select)(struct sched *s, struct task *t);
+       /**
+        * Answer a buffer tree query.
+        *
+        * This optional function pointer is used for inter node communications
+        * of the buffer tree nodes. See \ref btr_command_handler for details.
+        */
        btr_command_handler execute;
 };