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+<?xml version='1.0'?> <!--*-nxml-*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!--
+This file is part of systemd.
+
+Copyright 2014 Lennart Poettering
+
+systemd is free software; you can redistribute it and/or modify it
+under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+systemd is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with systemd; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<refentry id="sd_event_add_time" conditional="ENABLE_KDBUS">
+
+  <refentryinfo>
+    <title>sd_event_add_time</title>
+    <productname>systemd</productname>
+
+    <authorgroup>
+      <author>
+        <contrib>Developer</contrib>
+        <firstname>Lennart</firstname>
+        <surname>Poettering</surname>
+        <email>lennart@poettering.net</email>
+      </author>
+    </authorgroup>
+  </refentryinfo>
+
+  <refmeta>
+    <refentrytitle>sd_event_add_time</refentrytitle>
+    <manvolnum>3</manvolnum>
+  </refmeta>
+
+  <refnamediv>
+    <refname>sd_event_add_time</refname>
+    <refname>sd_event_source_get_time</refname>
+    <refname>sd_event_source_set_time</refname>
+    <refname>sd_event_source_get_time_accuracy</refname>
+    <refname>sd_event_source_set_time_accuracy</refname>
+    <refname>sd_event_source_get_time_clock</refname>
+
+    <refpurpose>Add a timer event source to an event loop</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <funcsynopsis>
+      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_add_time</function></funcdef>
+        <paramdef>sd_event *<parameter>event</parameter></paramdef>
+        <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
+        <paramdef>clockid_t <parameter>clock</parameter></paramdef>
+        <paramdef>uint64_t <parameter>usec</parameter></paramdef>
+        <paramdef>uint64_t <parameter>accuracy</parameter></paramdef>
+        <paramdef>sd_event_time_handler_t <parameter>handler</parameter></paramdef>
+        <paramdef>void* <parameter>userdata</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_source_get_time</function></funcdef>
+        <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+        <paramdef>usec_t* <parameter>usec</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_source_set_time</function></funcdef>
+        <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+        <paramdef>usec_t <parameter>usec</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_source_get_time_accuracy</function></funcdef>
+        <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+        <paramdef>usec_t *<parameter>usec</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_source_set_time_accuracy</function></funcdef>
+        <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+        <paramdef>usec_t <parameter>usec</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_source_get_time_clock</function></funcdef>
+        <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+        <paramdef>clockid_t *<parameter>clock</parameter></paramdef>
+      </funcprototype>
+
+    </funcsynopsis>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para><function>sd_event_add_time()</function> adds a new timer
+    event source to an event loop object. The event loop is specified
+    in <parameter>event</parameter>, the event source is returned in
+    the <parameter>source</parameter> parameter. The
+    <parameter>clock</parameter> parameter takes a clock identifier,
+    one of <constant>CLOCK_REALTIME</constant>,
+    <constant>CLOCK_MONOTONIC</constant> and
+    <constant>CLOCK_BOOTTIME_ALARM</constant>. See
+    <citerefentry><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+    for details regarding the various types of clocks. The
+    <parameter>usec</parameter> parameter takes a time value in
+    microseconds, relative to the clock's epoch specifying when the
+    timer shall elapse the earliest. The
+    <parameter>accuracy</parameter> parameter takes an additional
+    accuracy value in microseconds specifying a time the timer event
+    may be delayed. Specify 0 for selecting the default accuracy
+    (250ms). Specify 1 for most accurate timers. Consider specifying
+    60000000 or larger (1h) for long running events that may be
+    delayed substantially. Picking higher accuracy values allows the
+    system to coalesce timer events more aggressively, thus improving
+    power efficiency. The <parameter>handler</parameter> shall
+    reference a function to call when the timer elapses. The handler
+    function will be passed the <parameter>userdata</parameter>
+    pointer, which may be chosen freely by the caller. The handler is
+    also passed the configured time it was triggered, however it might
+    actually have been called at a slightly later time, subject to the
+    specified accuracy value, the kernel timer slack (see
+    <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>)
+    and additional scheduling latencies. By default the timer will
+    elapse once (SD_EVENT_ONESHOT), but this may be changed with
+    <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
+    the handler function returns a negative error code it will be
+    disabled after the invocation, even if SD_EVENT_ON mode is set.
+    </para>
+
+    <para><function>sd_event_source_get_time()</function> retrieves
+    the configured time value of a timer event source created
+    previously with <function>sd_event_add_time()</function>. It takes
+    the event source object and a pointer to a variable to store the
+    time in microseconds in.</para>
+
+    <para><function>sd_event_source_set_time()</function> changes the
+    configured time value of a timer event source created previously
+    with <function>sd_event_add_time()</function>. It takes the event
+    source object and a time relative to the selected clock's
+    epoch, in microseconds.</para>
+
+    <para><function>sd_event_source_get_time_accuracy()</function>
+    retrieves the configured accuracy value of a timer event source
+    created previously with <function>sd_event_add_time()</function>. It
+    takes the event source object and a pointer to a variable to store
+    the accuracy in microseconds in.</para>
+
+    <para><function>sd_event_source_set_time_accuracy()</function>
+    changes the configured accuracy of a timer event source created
+    previously with <function>sd_event_add_time()</function>. It takes
+    the event source object and an accuracy, in microseconds.</para>
+
+    <para><function>sd_event_source_get_time_clock()</function>
+    retrieves the configured clock of a timer event source created
+    previously with <function>sd_event_add_time()</function>. It takes
+    the event source object and a pointer to a variable to store the
+    clock identifier in.</para>
+
+  </refsect1>
+
+  <refsect1>
+    <title>Return Value</title>
+
+    <para>On success, these functions return 0 or a positive
+    integer. On failure, they return a negative errno-style error
+    code. </para>
+  </refsect1>
+
+  <refsect1>
+    <title>Errors</title>
+
+    <para>Returned errors may indicate the following problems:</para>
+
+    <variablelist>
+      <varlistentry>
+        <term><varname>-ENOMEM</varname></term>
+
+        <listitem><para>Not enough memory to allocate object.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>-EINVAL</varname></term>
+
+        <listitem><para>An invalid argument has been passed.</para></listitem>
+
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>-ESTALE</varname></term>
+
+        <listitem><para>The event loop is already terminated.</para></listitem>
+
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>-ECHILD</varname></term>
+
+        <listitem><para>The event loop has been created in a different process.</para></listitem>
+
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>-ENOTSUP</varname></term>
+
+        <listitem><para>The selected clock is not supported by the event loop implementation.</para></listitem>
+
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
+    <title>Notes</title>
+
+    <para><function>sd_event_add_time()</function> and the other functions
+    described here are available as a shared library, which can be
+    compiled and linked to with the
+    <constant>libsystemd</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+    file.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>See Also</title>
+
+    <para>
+      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    </para>
+  </refsect1>
+
+</refentry>