diff --git a/functions/dio.xml b/functions/dio.xml
index c5cdbca9f5..d5ffea8300 100644
--- a/functions/dio.xml
+++ b/functions/dio.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.5 $ -->
+<!-- $Revision: 1.6 $ -->
  <reference id="ref.dio">
   <title>Direct IO functions</title>
   <titleabbrev>DIO functions</titleabbrev>
@@ -236,7 +236,7 @@
   <refentry id="function.dio-fcntl">
    <refnamediv>
     <refname>dio_fcntl</refname>
-    <refpurpose>Perform a c library fcntl on fd </refpurpose>
+    <refpurpose>Performs a c library fcntl on fd </refpurpose>
    </refnamediv>
    <refsect1>
     <title>Description</title>
@@ -257,11 +257,40 @@
      additional arguments <parameter>args</parameter> to be supplied.
     </para>
     <para>
-     <parameter>cmd</parameter> can be one of the following
-     operations:
+    <parameter>arg</parameter> is an associative array, when
+    <parameter>cmd</parameter> is F_SETLK or F_SETLLW, with the
+    following keys:
+     <itemizedlist>
+      <listitem><para>"start" - offset where lock begins</para></listitem>
+      <listitem><para>"length" - size of locked area. zero means to
+      end of file</para></listitem>
+      <listitem><para>"wenth" - Where l_start is relative to: can be
+      SEEK_SET, SEEK_END and SEEK_CUR</para></listitem>
+      <listitem><para>"type" - type of lock: can be F_RDLCK (read
+      lock), F_WRLCK (write lock) or F_UNLCK (unlock)</para></listitem>
+     </itemizedlist>
     </para>
     <para>
-       cmd parameters still undocumented. 
+     <parameter>cmd</parameter> can be one of the following
+     operations:
+      <itemizedlist>
+        <listitem><para>F_SETLK - Lock is set or cleared. If the lock
+        is held by someone else <function>dio_fcntl</function> returns
+        -1.</para></listitem>
+        <listitem><para>F_SETLKW - like F_SETLK, but in case the lock
+        is held by someone else, <function>dio_fcntl</function> waits
+        until the lock is released.</para></listitem>
+        <listitem><para>F_GETLK - <function>dio_fcntl</function>
+        returns an associative array (as described above) if someone
+        else prevents lock. If there is no obstruction key "type"
+        will set to F_UNLCK.</para></listitem>
+        <listitem><para>F_DUPFD - finds the lowest numbered available
+        file descriptor greater or equal than
+        <parameter>arg</parameter> and returns them.</para></listitem>
+      </itemizedlist>
+   </para>
+    <para>
+
     </para>
    </refsect1>
   </refentry>