Adding upstream version 252.22.upstream/252.22upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 202 insertions, 0 deletions

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+<?xml version='1.0'?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
+
+<refentry id="sd_event_add_defer" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+  <refentryinfo>
+    <title>sd_event_add_defer</title>
+    <productname>systemd</productname>
+  </refentryinfo>
+
+  <refmeta>
+    <refentrytitle>sd_event_add_defer</refentrytitle>
+    <manvolnum>3</manvolnum>
+  </refmeta>
+
+  <refnamediv>
+    <refname>sd_event_add_defer</refname>
+    <refname>sd_event_add_post</refname>
+    <refname>sd_event_add_exit</refname>
+    <refname>sd_event_handler_t</refname>
+
+    <refpurpose>Add static event sources to an event loop</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <funcsynopsis>
+      <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
+
+      <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo>
+
+      <funcprototype>
+        <funcdef>typedef int (*<function>sd_event_handler_t</function>)</funcdef>
+        <paramdef>sd_event_source *<parameter>s</parameter></paramdef>
+        <paramdef>void *<parameter>userdata</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_add_defer</function></funcdef>
+        <paramdef>sd_event *<parameter>event</parameter></paramdef>
+        <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
+        <paramdef>sd_event_handler_t <parameter>handler</parameter></paramdef>
+        <paramdef>void *<parameter>userdata</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_add_post</function></funcdef>
+        <paramdef>sd_event *<parameter>event</parameter></paramdef>
+        <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
+        <paramdef>sd_event_handler_t <parameter>handler</parameter></paramdef>
+        <paramdef>void *<parameter>userdata</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_add_exit</function></funcdef>
+        <paramdef>sd_event *<parameter>event</parameter></paramdef>
+        <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
+        <paramdef>sd_event_handler_t <parameter>handler</parameter></paramdef>
+        <paramdef>void *<parameter>userdata</parameter></paramdef>
+      </funcprototype>
+
+    </funcsynopsis>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para>These three functions add new static event sources to an event loop. The event loop object is
+    specified in the <parameter>event</parameter> parameter, the event source object is returned in the
+    <parameter>source</parameter> parameter. The event sources are enabled statically and will "fire" when
+    the event loop is run and the conditions described below are met.</para>
+
+    <para>The <parameter>handler</parameter> is a function to call or <constant>NULL</constant>. The handler
+    function will be passed the <parameter>userdata</parameter> pointer, which may be chosen freely by the
+    caller. The handler may return negative to signal an error (see below), other return values are
+    ignored. If <parameter>handler</parameter> is <constant>NULL</constant>, a default handler that calls
+    <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry> will be
+    used.</para>
+
+    <para><function>sd_event_add_defer()</function> adds a new event
+    source that will be dispatched instantly, before the event loop
+    goes to sleep again and waits for new events. By default, the
+    handler will be called once
+    (<constant>SD_EVENT_ONESHOT</constant>). Note that if the event
+    source is set to <constant>SD_EVENT_ON</constant> the event loop
+    will never go to sleep again, but continuously call the handler,
+    possibly interleaved with other event sources.</para>
+
+    <para><function>sd_event_add_post()</function> adds a new event
+    source that is run before the event loop will sleep and wait
+    for new events, but only after at least one other non-post event
+    source was dispatched. By default, the source is enabled
+    permanently (<constant>SD_EVENT_ON</constant>). Note that this
+    event source type will still allow the event loop to go to sleep
+    again, even if set to <constant>SD_EVENT_ON</constant>, as long as
+    no other event source is ever triggered.</para>
+
+    <para><function>sd_event_add_exit()</function> adds a new event
+    source that will be dispatched when the event loop is terminated
+    with <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+
+    <para>The
+    <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    function may be used to enable the event source permanently
+    (<constant>SD_EVENT_ON</constant>) or to make it fire just once
+    (<constant>SD_EVENT_ONESHOT</constant>).</para>
+
+    <para>If the handler function returns a negative error code, it will either be disabled after the
+    invocation, even if the <constant>SD_EVENT_ON</constant> mode was requested before, or it will cause the
+    loop to terminate, see
+    <citerefentry><refentrytitle>sd_event_source_set_exit_on_failure</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+    </para>
+
+    <para>To destroy an event source object use
+    <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    but note that the event source is only removed from the event loop
+    when all references to the event source are dropped. To make sure
+    an event source does not fire anymore, even when there's still a
+    reference to it kept, consider setting the event source to
+    <constant>SD_EVENT_OFF</constant> with
+    <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+
+    <para>If the second parameter of these functions is passed as <constant>NULL</constant> no reference to
+    the event source object is returned. In this case the event source is considered "floating", and will be
+    destroyed implicitly when the event loop itself is destroyed.</para>
+
+    <para>If the <parameter>handler</parameter> parameter to <function>sd_event_add_defer()</function> or
+    <function>sd_event_add_post()</function> is <constant>NULL</constant>, and the event source fires, this
+    will be considered a request to exit the event loop. In this case, the <parameter>userdata</parameter>
+    parameter, cast to an integer, is passed as the exit code parameter to
+    <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Similar
+    functionality is not available for <function>sd_event_add_exit()</function>, as these types of event
+    sources are only dispatched when exiting anyway.</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>
+
+    <refsect2>
+      <title>Errors</title>
+
+      <para>Returned errors may indicate the following problems:</para>
+
+      <variablelist>
+        <varlistentry>
+          <term><constant>-ENOMEM</constant></term>
+
+          <listitem><para>Not enough memory to allocate an object.</para></listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>-EINVAL</constant></term>
+
+          <listitem><para>An invalid argument has been passed.</para></listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>-ESTALE</constant></term>
+
+          <listitem><para>The event loop is already terminated.</para></listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>-ECHILD</constant></term>
+
+          <listitem><para>The event loop has been created in a different process.</para></listitem>
+        </varlistentry>
+
+      </variablelist>
+    </refsect2>
+  </refsect1>
+
+  <xi:include href="libsystemd-pkgconfig.xml" />
+
+  <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>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_source_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    </para>
+  </refsect1>
+
+</refentry>