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1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
4 | ||
5 | <!-- | |
52ad194e MB |
6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
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8 | This file is part of systemd. |
9 | ||
10 | Copyright 2015 Lennart Poettering | |
11 | ||
12 | systemd is free software; you can redistribute it and/or modify it | |
13 | under the terms of the GNU Lesser General Public License as published by | |
14 | the Free Software Foundation; either version 2.1 of the License, or | |
15 | (at your option) any later version. | |
16 | ||
17 | systemd is distributed in the hope that it will be useful, but | |
18 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
20 | Lesser General Public License for more details. | |
21 | ||
22 | You should have received a copy of the GNU Lesser General Public License | |
23 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
24 | --> | |
25 | ||
26 | <refentry id="sd_event_source_set_prepare" xmlns:xi="http://www.w3.org/2001/XInclude"> | |
27 | ||
28 | <refentryinfo> | |
29 | <title>sd_event_source_set_prepare</title> | |
30 | <productname>systemd</productname> | |
31 | ||
32 | <authorgroup> | |
33 | <author> | |
34 | <contrib>Developer</contrib> | |
35 | <firstname>Lennart</firstname> | |
36 | <surname>Poettering</surname> | |
37 | <email>lennart@poettering.net</email> | |
38 | </author> | |
39 | </authorgroup> | |
40 | </refentryinfo> | |
41 | ||
42 | <refmeta> | |
43 | <refentrytitle>sd_event_source_set_prepare</refentrytitle> | |
44 | <manvolnum>3</manvolnum> | |
45 | </refmeta> | |
46 | ||
47 | <refnamediv> | |
48 | <refname>sd_event_source_set_prepare</refname> | |
49 | ||
50 | <refpurpose>Set a preparation callback for event sources</refpurpose> | |
51 | </refnamediv> | |
52 | ||
53 | <refsynopsisdiv> | |
54 | <funcsynopsis> | |
55 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> | |
56 | ||
57 | <funcprototype> | |
58 | <funcdef>int <function>sd_event_source_set_prepare</function></funcdef> | |
59 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
60 | <paramdef>sd_event_handler_t <parameter>callback</parameter></paramdef> | |
61 | </funcprototype> | |
62 | ||
63 | <funcprototype> | |
64 | <funcdef>typedef int (*<function>sd_event_handler_t</function>)</funcdef> | |
65 | <paramdef>sd_event_source *<parameter>s</parameter></paramdef> | |
66 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
67 | </funcprototype> | |
68 | ||
69 | </funcsynopsis> | |
70 | </refsynopsisdiv> | |
71 | ||
72 | <refsect1> | |
73 | <title>Description</title> | |
74 | ||
75 | <para><function>sd_event_source_set_prepare()</function> may be | |
76 | used to set a preparation callback for the event source object | |
77 | specified as <parameter>source</parameter>. The callback function | |
78 | specified as <parameter>callback</parameter> will be invoked | |
79 | immediately before the event loop goes to sleep to wait for | |
80 | incoming events. It is invoked with the user data pointer passed | |
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81 | when the event source was created. The event source will be disabled |
82 | if the callback function returns a negative error code. The callback | |
83 | function may be used to reconfigure the precise events to wait for. | |
84 | If the <parameter>callback</parameter> parameter is passed as NULL | |
85 | the callback function is reset. </para> | |
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86 | |
87 | <para>Event source objects have no preparation callback associated | |
88 | when they are first created with calls such as | |
89 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
90 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Preparation | |
91 | callback functions are supported for all event source types with | |
92 | the exception of those created with | |
93 | <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Preparation | |
94 | callback functions are dispatched in the order indicated by the | |
95 | event source's priority field, as set with | |
96 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Preparation | |
97 | callbacks of disabled event sources (see | |
98 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>) | |
99 | are not invoked.</para> | |
100 | </refsect1> | |
101 | ||
102 | <refsect1> | |
103 | <title>Return Value</title> | |
104 | ||
105 | <para>On success, | |
106 | <function>sd_event_source_set_prepare()</function> returns a | |
107 | non-negative integer. On failure, it returns a negative | |
108 | errno-style error code.</para> | |
109 | </refsect1> | |
110 | ||
111 | <refsect1> | |
112 | <title>Errors</title> | |
113 | ||
114 | <para>Returned errors may indicate the following problems:</para> | |
115 | ||
116 | <variablelist> | |
117 | <varlistentry> | |
118 | <term><constant>-EINVAL</constant></term> | |
119 | ||
120 | <listitem><para><parameter>source</parameter> is not a valid | |
121 | pointer to an <structname>sd_event_source</structname> | |
122 | object.</para></listitem> | |
123 | </varlistentry> | |
124 | ||
125 | <varlistentry> | |
126 | <term><constant>-ESTALE</constant></term> | |
127 | ||
128 | <listitem><para>The event loop is already terminated.</para></listitem> | |
129 | ||
130 | </varlistentry> | |
131 | <varlistentry> | |
132 | <term><constant>-ENOMEM</constant></term> | |
133 | ||
134 | <listitem><para>Not enough memory.</para></listitem> | |
135 | </varlistentry> | |
136 | ||
137 | <varlistentry> | |
138 | <term><constant>-ECHILD</constant></term> | |
139 | ||
140 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
141 | ||
142 | </varlistentry> | |
143 | ||
144 | <varlistentry> | |
145 | <term><constant>-EDOM</constant></term> | |
146 | ||
147 | <listitem><para>The specified event source has been created | |
148 | with | |
149 | <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem> | |
150 | ||
151 | </varlistentry> | |
152 | ||
153 | </variablelist> | |
154 | </refsect1> | |
155 | ||
156 | <xi:include href="libsystemd-pkgconfig.xml" /> | |
157 | ||
158 | <refsect1> | |
159 | <title>See Also</title> | |
160 | ||
161 | <para> | |
162 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
163 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
164 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
165 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
166 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
167 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
168 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
169 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
170 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
171 | </para> | |
172 | </refsect1> | |
173 | ||
174 | </refentry> |