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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 | <!-- | |
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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 | |
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11 | --> |
12 | ||
13 | <refentry id="sd_event_source_set_prepare" xmlns:xi="http://www.w3.org/2001/XInclude"> | |
14 | ||
15 | <refentryinfo> | |
16 | <title>sd_event_source_set_prepare</title> | |
17 | <productname>systemd</productname> | |
18 | ||
19 | <authorgroup> | |
20 | <author> | |
21 | <contrib>Developer</contrib> | |
22 | <firstname>Lennart</firstname> | |
23 | <surname>Poettering</surname> | |
24 | <email>lennart@poettering.net</email> | |
25 | </author> | |
26 | </authorgroup> | |
27 | </refentryinfo> | |
28 | ||
29 | <refmeta> | |
30 | <refentrytitle>sd_event_source_set_prepare</refentrytitle> | |
31 | <manvolnum>3</manvolnum> | |
32 | </refmeta> | |
33 | ||
34 | <refnamediv> | |
35 | <refname>sd_event_source_set_prepare</refname> | |
36 | ||
37 | <refpurpose>Set a preparation callback for event sources</refpurpose> | |
38 | </refnamediv> | |
39 | ||
40 | <refsynopsisdiv> | |
41 | <funcsynopsis> | |
42 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> | |
43 | ||
44 | <funcprototype> | |
45 | <funcdef>int <function>sd_event_source_set_prepare</function></funcdef> | |
46 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
47 | <paramdef>sd_event_handler_t <parameter>callback</parameter></paramdef> | |
48 | </funcprototype> | |
49 | ||
50 | <funcprototype> | |
51 | <funcdef>typedef int (*<function>sd_event_handler_t</function>)</funcdef> | |
52 | <paramdef>sd_event_source *<parameter>s</parameter></paramdef> | |
53 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
54 | </funcprototype> | |
55 | ||
56 | </funcsynopsis> | |
57 | </refsynopsisdiv> | |
58 | ||
59 | <refsect1> | |
60 | <title>Description</title> | |
61 | ||
62 | <para><function>sd_event_source_set_prepare()</function> may be | |
7f3fdb7f | 63 | used to set a preparation callback for the event source object |
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64 | specified as <parameter>source</parameter>. The callback function |
65 | specified as <parameter>callback</parameter> will be invoked | |
66 | immediately before the event loop goes to sleep to wait for | |
67 | incoming events. It is invoked with the user data pointer passed | |
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68 | when the event source was created. The event source will be disabled |
69 | if the callback function returns a negative error code. The callback | |
70 | function may be used to reconfigure the precise events to wait for. | |
71 | If the <parameter>callback</parameter> parameter is passed as NULL | |
72 | the callback function is reset. </para> | |
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73 | |
74 | <para>Event source objects have no preparation callback associated | |
75 | when they are first created with calls such as | |
76 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
77 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Preparation | |
78 | callback functions are supported for all event source types with | |
79 | the exception of those created with | |
80 | <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Preparation | |
81 | callback functions are dispatched in the order indicated by the | |
82 | event source's priority field, as set with | |
83 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Preparation | |
84 | callbacks of disabled event sources (see | |
85 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>) | |
86 | are not invoked.</para> | |
87 | </refsect1> | |
88 | ||
89 | <refsect1> | |
90 | <title>Return Value</title> | |
91 | ||
92 | <para>On success, | |
93 | <function>sd_event_source_set_prepare()</function> returns a | |
94 | non-negative integer. On failure, it returns a negative | |
95 | errno-style error code.</para> | |
96 | </refsect1> | |
97 | ||
98 | <refsect1> | |
99 | <title>Errors</title> | |
100 | ||
101 | <para>Returned errors may indicate the following problems:</para> | |
102 | ||
103 | <variablelist> | |
104 | <varlistentry> | |
105 | <term><constant>-EINVAL</constant></term> | |
106 | ||
107 | <listitem><para><parameter>source</parameter> is not a valid | |
108 | pointer to an <structname>sd_event_source</structname> | |
109 | object.</para></listitem> | |
110 | </varlistentry> | |
111 | ||
112 | <varlistentry> | |
113 | <term><constant>-ESTALE</constant></term> | |
114 | ||
115 | <listitem><para>The event loop is already terminated.</para></listitem> | |
116 | ||
117 | </varlistentry> | |
118 | <varlistentry> | |
119 | <term><constant>-ENOMEM</constant></term> | |
120 | ||
121 | <listitem><para>Not enough memory.</para></listitem> | |
122 | </varlistentry> | |
123 | ||
124 | <varlistentry> | |
125 | <term><constant>-ECHILD</constant></term> | |
126 | ||
127 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
128 | ||
129 | </varlistentry> | |
130 | ||
131 | <varlistentry> | |
132 | <term><constant>-EDOM</constant></term> | |
133 | ||
134 | <listitem><para>The specified event source has been created | |
135 | with | |
136 | <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem> | |
137 | ||
138 | </varlistentry> | |
139 | ||
140 | </variablelist> | |
141 | </refsect1> | |
142 | ||
143 | <xi:include href="libsystemd-pkgconfig.xml" /> | |
144 | ||
145 | <refsect1> | |
146 | <title>See Also</title> | |
147 | ||
148 | <para> | |
149 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
150 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
151 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
152 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
153 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
154 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
155 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
156 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
157 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
158 | </para> | |
159 | </refsect1> | |
160 | ||
161 | </refentry> |