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514094f9 | 1 | <?xml version='1.0'?> |
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2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
db9ecf05 | 4 | <!-- SPDX-License-Identifier: LGPL-2.1-or-later --> |
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5 | |
6 | <refentry id="sd_event_source_set_prepare" xmlns:xi="http://www.w3.org/2001/XInclude"> | |
7 | ||
8 | <refentryinfo> | |
9 | <title>sd_event_source_set_prepare</title> | |
10 | <productname>systemd</productname> | |
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11 | </refentryinfo> |
12 | ||
13 | <refmeta> | |
14 | <refentrytitle>sd_event_source_set_prepare</refentrytitle> | |
15 | <manvolnum>3</manvolnum> | |
16 | </refmeta> | |
17 | ||
18 | <refnamediv> | |
19 | <refname>sd_event_source_set_prepare</refname> | |
20 | ||
21 | <refpurpose>Set a preparation callback for event sources</refpurpose> | |
22 | </refnamediv> | |
23 | ||
24 | <refsynopsisdiv> | |
25 | <funcsynopsis> | |
26 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> | |
27 | ||
28 | <funcprototype> | |
29 | <funcdef>int <function>sd_event_source_set_prepare</function></funcdef> | |
30 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
31 | <paramdef>sd_event_handler_t <parameter>callback</parameter></paramdef> | |
32 | </funcprototype> | |
33 | ||
34 | <funcprototype> | |
35 | <funcdef>typedef int (*<function>sd_event_handler_t</function>)</funcdef> | |
36 | <paramdef>sd_event_source *<parameter>s</parameter></paramdef> | |
37 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
38 | </funcprototype> | |
39 | ||
40 | </funcsynopsis> | |
41 | </refsynopsisdiv> | |
42 | ||
43 | <refsect1> | |
44 | <title>Description</title> | |
45 | ||
46 | <para><function>sd_event_source_set_prepare()</function> may be | |
7f3fdb7f | 47 | used to set a preparation callback for the event source object |
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48 | specified as <parameter>source</parameter>. The callback function |
49 | specified as <parameter>callback</parameter> will be invoked | |
50 | immediately before the event loop goes to sleep to wait for | |
51 | incoming events. It is invoked with the user data pointer passed | |
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52 | when the event source was created. The event source will be disabled |
53 | if the callback function returns a negative error code. The callback | |
54 | function may be used to reconfigure the precise events to wait for. | |
6b44ad0b | 55 | If the <parameter>callback</parameter> parameter is passed as <constant>NULL</constant> |
95977da9 | 56 | the callback function is reset. </para> |
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57 | |
58 | <para>Event source objects have no preparation callback associated | |
59 | when they are first created with calls such as | |
60 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
61 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Preparation | |
62 | callback functions are supported for all event source types with | |
63 | the exception of those created with | |
64 | <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Preparation | |
65 | callback functions are dispatched in the order indicated by the | |
66 | event source's priority field, as set with | |
67 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Preparation | |
68 | callbacks of disabled event sources (see | |
69 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>) | |
70 | are not invoked.</para> | |
71 | </refsect1> | |
72 | ||
73 | <refsect1> | |
74 | <title>Return Value</title> | |
75 | ||
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76 | <para>On success, <function>sd_event_source_set_prepare()</function> returns a non-negative integer. On |
77 | failure, it returns a negative errno-style error code.</para> | |
dc83f27a | 78 | |
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79 | <refsect2> |
80 | <title>Errors</title> | |
dc83f27a | 81 | |
b1de39de | 82 | <para>Returned errors may indicate the following problems:</para> |
dc83f27a | 83 | |
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84 | <variablelist> |
85 | <varlistentry> | |
86 | <term><constant>-EINVAL</constant></term> | |
dc83f27a | 87 | |
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88 | <listitem><para><parameter>source</parameter> is not a valid pointer to an |
89 | <structname>sd_event_source</structname> object.</para></listitem> | |
90 | </varlistentry> | |
dc83f27a | 91 | |
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92 | <varlistentry> |
93 | <term><constant>-ESTALE</constant></term> | |
dc83f27a | 94 | |
b1de39de | 95 | <listitem><para>The event loop is already terminated.</para></listitem> |
dc83f27a | 96 | |
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97 | </varlistentry> |
98 | <varlistentry> | |
99 | <term><constant>-ENOMEM</constant></term> | |
dc83f27a | 100 | |
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101 | <listitem><para>Not enough memory.</para></listitem> |
102 | </varlistentry> | |
dc83f27a | 103 | |
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104 | <varlistentry> |
105 | <term><constant>-ECHILD</constant></term> | |
dc83f27a | 106 | |
b1de39de | 107 | <listitem><para>The event loop has been created in a different process.</para></listitem> |
dc83f27a | 108 | |
b1de39de | 109 | </varlistentry> |
dc83f27a | 110 | |
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111 | <varlistentry> |
112 | <term><constant>-EDOM</constant></term> | |
dc83f27a | 113 | |
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114 | <listitem><para>The specified event source has been created with |
115 | <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem> | |
dc83f27a | 116 | |
b1de39de | 117 | </varlistentry> |
dc83f27a | 118 | |
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119 | </variablelist> |
120 | </refsect2> | |
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121 | </refsect1> |
122 | ||
123 | <xi:include href="libsystemd-pkgconfig.xml" /> | |
124 | ||
125 | <refsect1> | |
126 | <title>See Also</title> | |
127 | ||
128 | <para> | |
129 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
130 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
131 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
dc83f27a | 132 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
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133 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
134 | <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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135 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
136 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
137 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
138 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
139 | </para> | |
140 | </refsect1> | |
141 | ||
142 | </refentry> |