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514094f9 | 1 | <?xml version='1.0'?> |
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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 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
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7 | --> |
8 | ||
9 | <refentry id="sd_event_source_set_prepare" xmlns:xi="http://www.w3.org/2001/XInclude"> | |
10 | ||
11 | <refentryinfo> | |
12 | <title>sd_event_source_set_prepare</title> | |
13 | <productname>systemd</productname> | |
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14 | </refentryinfo> |
15 | ||
16 | <refmeta> | |
17 | <refentrytitle>sd_event_source_set_prepare</refentrytitle> | |
18 | <manvolnum>3</manvolnum> | |
19 | </refmeta> | |
20 | ||
21 | <refnamediv> | |
22 | <refname>sd_event_source_set_prepare</refname> | |
23 | ||
24 | <refpurpose>Set a preparation callback for event sources</refpurpose> | |
25 | </refnamediv> | |
26 | ||
27 | <refsynopsisdiv> | |
28 | <funcsynopsis> | |
29 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> | |
30 | ||
31 | <funcprototype> | |
32 | <funcdef>int <function>sd_event_source_set_prepare</function></funcdef> | |
33 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
34 | <paramdef>sd_event_handler_t <parameter>callback</parameter></paramdef> | |
35 | </funcprototype> | |
36 | ||
37 | <funcprototype> | |
38 | <funcdef>typedef int (*<function>sd_event_handler_t</function>)</funcdef> | |
39 | <paramdef>sd_event_source *<parameter>s</parameter></paramdef> | |
40 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
41 | </funcprototype> | |
42 | ||
43 | </funcsynopsis> | |
44 | </refsynopsisdiv> | |
45 | ||
46 | <refsect1> | |
47 | <title>Description</title> | |
48 | ||
49 | <para><function>sd_event_source_set_prepare()</function> may be | |
7f3fdb7f | 50 | used to set a preparation callback for the event source object |
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51 | specified as <parameter>source</parameter>. The callback function |
52 | specified as <parameter>callback</parameter> will be invoked | |
53 | immediately before the event loop goes to sleep to wait for | |
54 | incoming events. It is invoked with the user data pointer passed | |
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55 | when the event source was created. The event source will be disabled |
56 | if the callback function returns a negative error code. The callback | |
57 | function may be used to reconfigure the precise events to wait for. | |
58 | If the <parameter>callback</parameter> parameter is passed as NULL | |
59 | the callback function is reset. </para> | |
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60 | |
61 | <para>Event source objects have no preparation callback associated | |
62 | when they are first created with calls such as | |
63 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
64 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Preparation | |
65 | callback functions are supported for all event source types with | |
66 | the exception of those created with | |
67 | <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Preparation | |
68 | callback functions are dispatched in the order indicated by the | |
69 | event source's priority field, as set with | |
70 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Preparation | |
71 | callbacks of disabled event sources (see | |
72 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>) | |
73 | are not invoked.</para> | |
74 | </refsect1> | |
75 | ||
76 | <refsect1> | |
77 | <title>Return Value</title> | |
78 | ||
79 | <para>On success, | |
80 | <function>sd_event_source_set_prepare()</function> returns a | |
81 | non-negative integer. On failure, it returns a negative | |
82 | errno-style error code.</para> | |
83 | </refsect1> | |
84 | ||
85 | <refsect1> | |
86 | <title>Errors</title> | |
87 | ||
88 | <para>Returned errors may indicate the following problems:</para> | |
89 | ||
90 | <variablelist> | |
91 | <varlistentry> | |
92 | <term><constant>-EINVAL</constant></term> | |
93 | ||
94 | <listitem><para><parameter>source</parameter> is not a valid | |
95 | pointer to an <structname>sd_event_source</structname> | |
96 | object.</para></listitem> | |
97 | </varlistentry> | |
98 | ||
99 | <varlistentry> | |
100 | <term><constant>-ESTALE</constant></term> | |
101 | ||
102 | <listitem><para>The event loop is already terminated.</para></listitem> | |
103 | ||
104 | </varlistentry> | |
105 | <varlistentry> | |
106 | <term><constant>-ENOMEM</constant></term> | |
107 | ||
108 | <listitem><para>Not enough memory.</para></listitem> | |
109 | </varlistentry> | |
110 | ||
111 | <varlistentry> | |
112 | <term><constant>-ECHILD</constant></term> | |
113 | ||
114 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
115 | ||
116 | </varlistentry> | |
117 | ||
118 | <varlistentry> | |
119 | <term><constant>-EDOM</constant></term> | |
120 | ||
121 | <listitem><para>The specified event source has been created | |
122 | with | |
123 | <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem> | |
124 | ||
125 | </varlistentry> | |
126 | ||
127 | </variablelist> | |
128 | </refsect1> | |
129 | ||
130 | <xi:include href="libsystemd-pkgconfig.xml" /> | |
131 | ||
132 | <refsect1> | |
133 | <title>See Also</title> | |
134 | ||
135 | <para> | |
136 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
137 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
138 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
139 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
140 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
141 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
142 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
143 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
144 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
145 | </para> | |
146 | </refsect1> | |
147 | ||
148 | </refentry> |