sd-bus: Add sd_bus_reply_method_return docs + cleanups

[thirdparty/systemd.git] / man / sd_bus_call.xml

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<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 &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>

      <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. 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> returns an error, <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> shall reference a function to call
    when the event source is triggered. 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. The <parameter>callback</parameter> function is called when the response arrives
    and receives the response, <parameter>userdata</parameter> and a
    <structname>sd_bus_error</structname> object as its arguments. The
    <structname>sd_bus_error</structname> object is unused here and should be ignored. If
    <parameter>callback</parameter> returns a non-negative integer when called, a debug message is
    logged along with details about the response.</para>

    <para>To determine whether the method call succeeded, use
    <citerefentry><refentrytitle>sd_bus_message_is_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    on the reply object returned by <function>sd_bus_call()</function> or passed to the callback of
    <function>sd_bus_call_async()</function>.</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>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></listitem>

          <listitem><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></listitem>

          <listitem><para>The input parameter <parameter>m</parameter> has the
          <constant>BUS_MESSAGE_NO_REPLY_EXPECTED</constant> flag set.</para></listitem>

          <listitem><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 bus 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 client was disconnected 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>See Also</title>

    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_call_method</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_call_method_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>