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1 | <?xml version='1.0'?> |
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_bus_call" | |
7 | xmlns:xi="http://www.w3.org/2001/XInclude"> | |
8 | ||
9 | <refentryinfo> | |
10 | <title>sd_bus_call</title> | |
11 | <productname>systemd</productname> | |
12 | </refentryinfo> | |
13 | ||
14 | <refmeta> | |
15 | <refentrytitle>sd_bus_call</refentrytitle> | |
16 | <manvolnum>3</manvolnum> | |
17 | </refmeta> | |
18 | ||
19 | <refnamediv> | |
20 | <refname>sd_bus_call</refname> | |
21 | <refname>sd_bus_call_async</refname> | |
22 | ||
23 | <refpurpose>Invoke a D-Bus method call</refpurpose> | |
24 | </refnamediv> | |
25 | ||
26 | <refsynopsisdiv> | |
27 | <funcsynopsis> | |
28 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
29 | ||
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30 | <xi:include href="sd_bus_add_match.xml" xpointer="sd_bus_message_handler_t"/> |
31 | ||
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32 | <funcprototype> |
33 | <funcdef>int <function>sd_bus_call</function></funcdef> | |
34 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
35 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
36 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> | |
37 | <paramdef>sd_bus_error *<parameter>ret_error</parameter></paramdef> | |
38 | <paramdef>sd_bus_message **<parameter>reply</parameter></paramdef> | |
39 | </funcprototype> | |
40 | ||
41 | <funcprototype> | |
42 | <funcdef>int <function>sd_bus_call_async</function></funcdef> | |
43 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
44 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
45 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
46 | <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> | |
47 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
48 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> | |
49 | </funcprototype> | |
50 | </funcsynopsis> | |
51 | </refsynopsisdiv> | |
52 | ||
53 | <refsect1> | |
54 | <title>Description</title> | |
55 | ||
56 | <para><function>sd_bus_call()</function> takes a complete bus message object and calls the | |
47203ed0 | 57 | corresponding D-Bus method. On success, the response is stored in <parameter>reply</parameter>. |
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58 | <parameter>usec</parameter> indicates the timeout in microseconds. If |
59 | <parameter>ret_error</parameter> is not <constant>NULL</constant> and | |
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60 | <function>sd_bus_call()</function> fails (either because of an internal error or because it |
61 | received a D-Bus error reply), <parameter>ret_error</parameter> is initialized to an instance of | |
62 | <structname>sd_bus_error</structname> describing the error.</para> | |
953ee402 | 63 | |
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64 | <para><function>sd_bus_call_async()</function> is like <function>sd_bus_call()</function> but works |
65 | asynchronously. The <parameter>callback</parameter> indicates the function to call when the response | |
66 | arrives. The <parameter>userdata</parameter> pointer will be passed to the callback function, and may be | |
67 | chosen freely by the caller. If <parameter>slot</parameter> is not <constant>NULL</constant> and | |
68 | <function>sd_bus_call_async()</function> succeeds, <parameter>slot</parameter> is set to a slot object | |
69 | which can be used to cancel the method call at a later time using | |
953ee402 | 70 | <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>. |
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71 | If <parameter>slot</parameter> is <constant>NULL</constant>, the lifetime of the method call is bound to |
72 | the lifetime of the bus object itself, and it cannot be cancelled independently. See | |
953ee402 | 73 | <citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
47203ed0 | 74 | for details. <parameter>callback</parameter> is called when a reply arrives with the reply, |
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75 | <parameter>userdata</parameter> and an <structname>sd_bus_error</structname> output parameter as its |
76 | arguments. Unlike <function>sd_bus_call()</function>, the <structname>sd_bus_error</structname> output | |
77 | parameter passed to the callback will be empty. To determine whether the method call succeeded, use | |
953ee402 | 78 | <citerefentry><refentrytitle>sd_bus_message_is_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
47203ed0 | 79 | on the reply message passed to the callback instead. If the callback returns zero and the |
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80 | <structname>sd_bus_error</structname> output parameter is still empty when the callback finishes, other |
81 | handlers registered with functions such as | |
47203ed0 | 82 | <citerefentry><refentrytitle>sd_bus_add_filter</refentrytitle><manvolnum>3</manvolnum></citerefentry> or |
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83 | <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry> are |
84 | given a chance to process the message. If the callback returns a non-zero value or the | |
85 | <structname>sd_bus_error</structname> output parameter is not empty when the callback finishes, no | |
86 | further processing of the message is done. Generally, you want to return zero from the callback to give | |
87 | other registered handlers a chance to process the reply as well. (Note that the | |
88 | <structname>sd_bus_error</structname> parameter is an output parameter of the callback function, not an | |
89 | input parameter; it can be used to propagate errors from the callback handler, it will not receive any | |
90 | error that was received as method reply.)</para> | |
953ee402 | 91 | |
e6ce785d | 92 | <para>The message <parameter>m</parameter> passed to the callback is only borrowed, that is, the callback should |
93 | not call <citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
94 | on it. If the callback wants to hold on to the message beyond the lifetime of the callback, it needs to call | |
95 | <citerefentry><refentrytitle>sd_bus_message_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to create a | |
96 | new reference.</para> | |
97 | ||
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98 | <para>If <parameter>usec</parameter> is zero, the default D-Bus method call timeout is used. See |
99 | <citerefentry><refentrytitle>sd_bus_get_method_call_timeout</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
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100 | </para> |
101 | ||
102 | </refsect1> | |
103 | ||
104 | <refsect1> | |
105 | <title>Return Value</title> | |
106 | ||
107 | <para>On success, these functions return a non-negative integer. On failure, they return a | |
108 | negative errno-style error code.</para> | |
109 | ||
110 | <refsect2 id='errors'> | |
111 | <title>Errors</title> | |
112 | ||
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113 | <para>When <function>sd_bus_call()</function> internally receives a D-Bus error reply, it will set |
114 | <parameter>ret_error</parameter> if it is not <constant>NULL</constant>, and will return a negative | |
115 | value mapped from the error reply, see | |
c660668e YW |
116 | <citerefentry><refentrytitle>sd_bus_error_get_errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>. |
117 | </para> | |
953ee402 | 118 | |
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119 | <para>Returned errors may indicate the following problems:</para> |
120 | ||
121 | <variablelist> | |
122 | <varlistentry> | |
123 | <term><constant>-EINVAL</constant></term> | |
124 | ||
125 | <listitem><para>The input parameter <parameter>m</parameter> is <constant>NULL</constant>. | |
126 | </para></listitem> | |
127 | ||
128 | <listitem><para>The input parameter <parameter>m</parameter> is not a D-Bus method call. | |
129 | To create a new D-Bus method call, use | |
130 | <citerefentry><refentrytitle>sd_bus_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
131 | </para></listitem> | |
132 | ||
133 | <listitem><para>The input parameter <parameter>m</parameter> has the | |
134 | <constant>BUS_MESSAGE_NO_REPLY_EXPECTED</constant> flag set.</para></listitem> | |
135 | ||
136 | <listitem><para>The input parameter <parameter>error</parameter> is | |
137 | non-<constant>NULL</constant> but was not set to <constant>SD_BUS_ERROR_NULL</constant>. | |
138 | </para></listitem> | |
139 | </varlistentry> | |
140 | ||
141 | <varlistentry> | |
142 | <term><constant>-ECHILD</constant></term> | |
143 | ||
144 | <listitem><para>The bus connection was allocated in a parent process and is being reused | |
145 | in a child process after <function>fork()</function>.</para></listitem> | |
146 | </varlistentry> | |
147 | ||
148 | <varlistentry> | |
149 | <term><constant>-ENOTCONN</constant></term> | |
150 | ||
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151 | <listitem><para>The input parameter <parameter>bus</parameter> is |
152 | <constant>NULL</constant> or the bus is not connected.</para></listitem> | |
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153 | </varlistentry> |
154 | ||
155 | <varlistentry> | |
156 | <term><constant>-ECONNRESET</constant></term> | |
157 | ||
b0f4c02e | 158 | <listitem><para>The bus connection was closed while waiting for the response. |
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159 | </para></listitem> |
160 | </varlistentry> | |
161 | ||
162 | <varlistentry> | |
163 | <term><constant>-ETIMEDOUT</constant></term> | |
164 | ||
165 | <listitem><para>A response was not received within the given timeout.</para></listitem> | |
166 | </varlistentry> | |
167 | ||
168 | <varlistentry> | |
169 | <term><constant>-ELOOP</constant></term> | |
170 | ||
171 | <listitem><para>The message <parameter>m</parameter> is addressed to its own client. | |
172 | </para></listitem> | |
173 | </varlistentry> | |
174 | ||
175 | <varlistentry> | |
176 | <term><constant>-ENOMEM</constant></term> | |
177 | ||
178 | <listitem><para>Memory allocation failed.</para></listitem> | |
179 | </varlistentry> | |
180 | </variablelist> | |
181 | </refsect2> | |
182 | </refsect1> | |
183 | ||
184 | <xi:include href="libsystemd-pkgconfig.xml" /> | |
185 | ||
186 | <refsect1> | |
187 | <title>See Also</title> | |
188 | ||
189 | <para> | |
190 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
191 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
192 | <citerefentry><refentrytitle>sd_bus_call_method</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
193 | <citerefentry><refentrytitle>sd_bus_call_method_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
194 | <citerefentry><refentrytitle>sd_bus_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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195 | <citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
196 | <citerefentry><refentrytitle>sd_bus_error</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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197 | </para> |
198 | </refsect1> | |
199 | ||
200 | </refentry> |