filter.h: Improve documentation of ->pre_select().

Fix a grammar issue ("it only allowed") and explain the purpose of
the fd sets.

diff --git a/filter.h b/filter.h
index 135a6887405e496ef7c44154886d449c1e3e8156..7ae28fe4946a578b0d0f229359f740252de4b1b9 100644 (file)
--- a/filter.h
+++ b/filter.h
@@ -96,10 +96,12 @@ struct filter {
        /**
         * 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.
+        * This function controls the timeout value for the next call to
+        * select(2). It may decrease the current timeout but shall never
+        * increase it. The second purpose of this function is to add file
+        * descriptors to the two fd sets of the sched structure. The
+        * descriptors in these sets will be watched by the subsequent
+        * select(2) call.
         */
        void (*pre_select)(struct sched *s, void *context);
        /**