mirror of
https://github.com/systemd/systemd.git
synced 2024-11-23 18:23:32 +08:00
209 lines
10 KiB
XML
209 lines
10 KiB
XML
<?xml version='1.0'?>
|
|
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
|
|
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
|
|
|
|
<refentry id="sd_bus_call"
|
|
xmlns:xi="http://www.w3.org/2001/XInclude">
|
|
|
|
<refentryinfo>
|
|
<title>sd_bus_call</title>
|
|
<productname>systemd</productname>
|
|
</refentryinfo>
|
|
|
|
<refmeta>
|
|
<refentrytitle>sd_bus_call</refentrytitle>
|
|
<manvolnum>3</manvolnum>
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>sd_bus_call</refname>
|
|
<refname>sd_bus_call_async</refname>
|
|
|
|
<refpurpose>Invoke a D-Bus method call</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<funcsynopsis>
|
|
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
|
|
|
|
<xi:include href="sd_bus_add_match.xml" xpointer="sd_bus_message_handler_t"/>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_bus_call</function></funcdef>
|
|
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
|
<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
|
|
<paramdef>uint64_t <parameter>usec</parameter></paramdef>
|
|
<paramdef>sd_bus_error *<parameter>ret_error</parameter></paramdef>
|
|
<paramdef>sd_bus_message **<parameter>reply</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_bus_call_async</function></funcdef>
|
|
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
|
<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
|
|
<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
|
|
<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
|
|
<paramdef>void *<parameter>userdata</parameter></paramdef>
|
|
<paramdef>uint64_t <parameter>usec</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1>
|
|
<title>Description</title>
|
|
|
|
<para><function>sd_bus_call()</function> takes a complete bus message object and calls the
|
|
corresponding D-Bus method. On success, the response is stored in <parameter>reply</parameter>.
|
|
<parameter>usec</parameter> indicates the timeout in microseconds. If
|
|
<parameter>ret_error</parameter> is not <constant>NULL</constant> and
|
|
<function>sd_bus_call()</function> fails (either because of an internal error or because it
|
|
received a D-Bus error reply), <parameter>ret_error</parameter> is initialized to an instance of
|
|
<structname>sd_bus_error</structname> describing the error.</para>
|
|
|
|
<para><function>sd_bus_call_async()</function> is like <function>sd_bus_call()</function> but works
|
|
asynchronously. The <parameter>callback</parameter> indicates the function to call when the response
|
|
arrives. The <parameter>userdata</parameter> pointer will be passed to the callback function, and may be
|
|
chosen freely by the caller. If <parameter>slot</parameter> is not <constant>NULL</constant> and
|
|
<function>sd_bus_call_async()</function> succeeds, <parameter>slot</parameter> is set to a slot object
|
|
which can be used to cancel the method call at a later time using
|
|
<citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
|
If <parameter>slot</parameter> is <constant>NULL</constant>, the lifetime of the method call is bound to
|
|
the lifetime of the bus object itself, and it cannot be cancelled independently. See
|
|
<citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
for details. <parameter>callback</parameter> is called when a reply arrives with the reply,
|
|
<parameter>userdata</parameter> and an <structname>sd_bus_error</structname> output parameter as its
|
|
arguments. Unlike <function>sd_bus_call()</function>, the <structname>sd_bus_error</structname> output
|
|
parameter passed to the callback will be empty. To determine whether the method call succeeded, use
|
|
<citerefentry><refentrytitle>sd_bus_message_is_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
on the reply message passed to the callback instead. If the callback returns zero and the
|
|
<structname>sd_bus_error</structname> output parameter is still empty when the callback finishes, other
|
|
handlers registered with functions such as
|
|
<citerefentry><refentrytitle>sd_bus_add_filter</refentrytitle><manvolnum>3</manvolnum></citerefentry> or
|
|
<citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry> are
|
|
given a chance to process the message. If the callback returns a non-zero value or the
|
|
<structname>sd_bus_error</structname> output parameter is not empty when the callback finishes, no
|
|
further processing of the message is done. Generally, you want to return zero from the callback to give
|
|
other registered handlers a chance to process the reply as well. (Note that the
|
|
<structname>sd_bus_error</structname> parameter is an output parameter of the callback function, not an
|
|
input parameter; it can be used to propagate errors from the callback handler, it will not receive any
|
|
error that was received as method reply.)</para>
|
|
|
|
<para>The message <parameter>m</parameter> passed to the callback is only borrowed, that is, the callback should
|
|
not call <citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
on it. If the callback wants to hold on to the message beyond the lifetime of the callback, it needs to call
|
|
<citerefentry><refentrytitle>sd_bus_message_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to create a
|
|
new reference.</para>
|
|
|
|
<para>If <parameter>usec</parameter> is zero, the default D-Bus method call timeout is used. See
|
|
<citerefentry><refentrytitle>sd_bus_get_method_call_timeout</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
|
</para>
|
|
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Return Value</title>
|
|
|
|
<para>On success, these functions return a non-negative integer. On failure, they return a
|
|
negative errno-style error code.</para>
|
|
|
|
<refsect2 id='errors'>
|
|
<title>Errors</title>
|
|
|
|
<para>When <function>sd_bus_call()</function> internally receives a D-Bus error reply, it will set
|
|
<parameter>ret_error</parameter> if it is not <constant>NULL</constant>, and will return a negative
|
|
value mapped from the error reply, see
|
|
<citerefentry><refentrytitle>sd_bus_error_get_errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
|
</para>
|
|
|
|
<para>Returned errors may indicate the following problems:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><constant>-EINVAL</constant></term>
|
|
|
|
<listitem>
|
|
<para>The input parameter <parameter>m</parameter> is <constant>NULL</constant>.
|
|
</para>
|
|
|
|
<para>The input parameter <parameter>m</parameter> is not a D-Bus method call.
|
|
To create a new D-Bus method call, use
|
|
<citerefentry><refentrytitle>sd_bus_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
|
</para>
|
|
|
|
<para>The input parameter <parameter>m</parameter> has the
|
|
<constant>BUS_MESSAGE_NO_REPLY_EXPECTED</constant> flag set.</para>
|
|
|
|
<para>The input parameter <parameter>error</parameter> is
|
|
non-<constant>NULL</constant> but was not set to <constant>SD_BUS_ERROR_NULL</constant>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-ECHILD</constant></term>
|
|
|
|
<listitem><para>The bus connection was allocated in a parent process and is being reused
|
|
in a child process after <function>fork()</function>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-ENOTCONN</constant></term>
|
|
|
|
<listitem><para>The input parameter <parameter>bus</parameter> is
|
|
<constant>NULL</constant> or the bus is not connected.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-ECONNRESET</constant></term>
|
|
|
|
<listitem><para>The bus connection was closed while waiting for the response.
|
|
</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-ETIMEDOUT</constant></term>
|
|
|
|
<listitem><para>A response was not received within the given timeout.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-ELOOP</constant></term>
|
|
|
|
<listitem><para>The message <parameter>m</parameter> is addressed to its own client.
|
|
</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-ENOMEM</constant></term>
|
|
|
|
<listitem><para>Memory allocation failed.</para></listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect2>
|
|
</refsect1>
|
|
|
|
<xi:include href="libsystemd-pkgconfig.xml" />
|
|
|
|
<refsect1>
|
|
<title>History</title>
|
|
<para><function>sd_bus_call()</function> and
|
|
<function>sd_bus_call_async()</function> were added in version 221.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>See Also</title>
|
|
|
|
<para><simplelist type="inline">
|
|
<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>sd_bus_call_method</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>sd_bus_call_method_async</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>sd_bus_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>sd_bus_error</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
|
|
</simplelist></para>
|
|
</refsect1>
|
|
|
|
</refentry>
|