man: document the new sd_event_add_inotify() call

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+<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
+
+<refentry id="sd_event_add_inotify" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+  <refentryinfo>
+    <title>sd_event_add_inotify</title>
+    <productname>elogind</productname>
+  </refentryinfo>
+
+  <refmeta>
+    <refentrytitle>sd_event_add_inotify</refentrytitle>
+    <manvolnum>3</manvolnum>
+  </refmeta>
+
+  <refnamediv>
+    <refname>sd_event_add_inotify</refname>
+    <refname>sd_event_source_get_inotify_mask</refname>
+    <refname>sd_event_inotify_handler_t</refname>
+
+    <refpurpose>Add an "inotify" file system inode event source to an event loop</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <funcsynopsis>
+      <funcsynopsisinfo>#include &lt;elogind/sd-event.h&gt;</funcsynopsisinfo>
+
+      <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo>
+
+      <funcprototype>
+        <funcdef>typedef int (*<function>sd_event_inotify_handler_t</function>)</funcdef>
+        <paramdef>sd_event_source *<parameter>s</parameter></paramdef>
+        <paramdef>const struct inotify_event *<parameter>event</parameter></paramdef>
+        <paramdef>void *<parameter>userdata</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_add_inotify</function></funcdef>
+        <paramdef>sd_event *<parameter>event</parameter></paramdef>
+        <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
+        <paramdef>const char *<parameter>path</parameter></paramdef>
+        <paramdef>uint32_t <parameter>mask</parameter></paramdef>
+        <paramdef>sd_event_inotify_handler_t <parameter>handler</parameter></paramdef>
+        <paramdef>void *<parameter>userdata</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_source_get_inotify_mask</function></funcdef>
+        <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+        <paramdef>uint32_t *<parameter>mask</parameter></paramdef>
+      </funcprototype>
+
+    </funcsynopsis>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para><function>sd_event_add_inotify()</function> adds a new <citerefentry
+    project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry> file system inode
+    event source 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 <parameter>path</parameter>
+    parameter specifies the path of the file system inode to watch. The <parameter>handler</parameter> must reference a
+    function to call when the inode changes. The handler function will be passed the <parameter>userdata</parameter>
+    pointer, which may be chosen freely by the caller. The handler also receives a pointer to a <structname>struct
+    inotify_event</structname> structure containing information about the inode event. The <parameter>mask</parameter>
+    parameter specifie which types of inode events to watch specifically. It must contain an OR-ed combination of
+    <constant>IN_ACCESS</constant>, <constant>IN_ATTRIB</constant>, <constant>IN_CLOSE_WRITE</constant>, … flags. See
+    <citerefentry project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
+    further information.</para>
+
+    <para>If multiple event sources are installed for the same inode the backing inotify watch descriptor is
+    automatically shared. The mask parameter may contain any flag defined by the inotify API, with the exception of
+    <constant>IN_MASK_ADD</constant>.</para>
+
+    <para>The handler is enabled continuously (<constant>SD_EVENT_ON</constant>), but this may be changed with
+    <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Alternatively,
+    the <constant>IN_ONESHOT</constant> mask flag may be used to request <constant>SD_EVENT_ONESHOT</constant> mode.
+    If the handler function returns a negative error code, it will be disabled after the invocation, even if the
+    <constant>SD_EVENT_ON</constant> mode was requested before.
+    </para>
+
+    <para>As a special limitation the priority of inotify event sources may only be altered (see
+    <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>)
+    in the time between creation of the event source object with <function>sd_event_add_inotify()</function> and the
+    beginning of the next event loop iteration. Attempts of changing the priority any later will be refused. Consider
+    freeing and allocating a new inotify event source to change the priority at that point.</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 disabling
+    it with
+    <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+
+    <para>If the second parameter of <function>sd_event_add_inotify()</function> is passed as NULL 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><function>sd_event_source_get_inotify_mask()</function> retrieves the configured inotify watch mask of an
+    event source created previously with <function>sd_event_add_inotify()</function>. It takes the event source object
+    as the <parameter>source</parameter> parameter and a pointer to a <type>uint32_t</type> variable to return the mask
+    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><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. This includes specifying a mask with
+        <constant>IN_MASK_ADD</constant> set.</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>
+
+      <varlistentry>
+        <term><constant>-EDOM</constant></term>
+
+        <listitem><para>The passed event source is not an inotify process event source.</para></listitem>
+      </varlistentry>
+
+    </variablelist>
+  </refsect1>
+
+  <xi:include href="libelogind-pkgconfig.xml" />
+
+  <refsect1>
+    <title>See Also</title>
+
+    <para>
+      <citerefentry><refentrytitle>elogind</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_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_add_child</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 project='man-pages'><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+    </para>
+  </refsect1>
+
+</refentry>