<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>
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
+ <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
+ 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
+ <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
- inishes, other handlers registered with functions such as
+ <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.</para>
+ <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>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>.