man/sd_bus_slot_set_floating.xml

   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">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="sd_bus_slot_set_floating" xmlns:xi="http://www.w3.org/2001/XInclude">
   7
   8   <refentryinfo>
   9     <title>sd_bus_slot_set_floating</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>sd_bus_slot_set_floating</refentrytitle>
  15     <manvolnum>3</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>sd_bus_slot_set_floating</refname>
  20     <refname>sd_bus_slot_get_floating</refname>
  21
  22     <refpurpose>Control whether a bus slot object is "floating".</refpurpose>
  23   </refnamediv>
  24
  25   <refsynopsisdiv>
  26     <funcsynopsis>
  27       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  28
  29       <funcprototype>
  30         <funcdef>int <function>sd_bus_slot_set_floating</function></funcdef>
  31         <paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
  32         <paramdef>int <parameter>b</parameter></paramdef>
  33       </funcprototype>
  34
  35       <funcprototype>
  36         <funcdef>int <function>sd_bus_slot_get_floating</function></funcdef>
  37         <paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
  38       </funcprototype>
  39
  40     </funcsynopsis>
  41   </refsynopsisdiv>
  42
  43   <refsect1>
  44     <title>Description</title>
  45
  46     <para><function>sd_bus_slot_set_floating()</function> controls whether the specified bus slot object
  47     <parameter>slot</parameter> shall be "floating" or not. A floating bus slot object's lifetime is bound to the
  48     lifetime of the bus object it is associated with, meaning that it remains allocated as long as the bus object
  49     itself and is freed automatically when the bus object is freed. Regular (i.e. non-floating) bus slot objects keep
  50     the bus referenced, hence the bus object remains allocated at least as long as there remains at least one
  51     referenced bus slot object around. The floating state hence controls the direction of referencing between the bus
  52     object and the bus slot objects: if floating the bus pins the bus slot, and otherwise the bus slot pins the bus
  53     objects. Use <function>sd_bus_slot_set_floating()</function> to switch between both modes: if the
  54     <parameter>b</parameter> parameter is zero, the slot object is considered floating, otherwise it is made a regular
  55     (non-floating) slot object.</para>
  56
  57     <para>Bus slot objects may be allocated with calls such as
  58     <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If the
  59     <parameter>slot</parameter> of these functions is non-<constant>NULL</constant> the slot object will be of the
  60     regular kind (i.e. non-floating), otherwise it will be created floating. With
  61     <function>sd_bus_slot_set_floating()</function> a bus slot object allocated as regular can be converted into a
  62     floating object and back. This is particularly useful for creating a bus slot object, then changing parameters of
  63     it, and then turning it into a floating object, whose lifecycle is managed by the bus object.</para>
  64
  65     <para><function>sd_bus_slot_get_floating()</function> returns the current floating state of the specified bus slot
  66     object. It returns negative on error, zero if the bus slot object is a regular (non-floating) object and positive
  67     otherwise.</para>
  68   </refsect1>
  69
  70   <refsect1>
  71     <title>Return Value</title>
  72
  73     <para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style
  74     error code.</para>
  75   </refsect1>
  76
  77   <refsect1>
  78     <title>Errors</title>
  79
  80     <para>Returned errors may indicate the following problems:</para>
  81
  82     <variablelist>
  83       <varlistentry>
  84         <term><constant>-EINVAL</constant></term>
  85
  86         <listitem><para>The <parameter>slot</parameter> parameter is <constant>NULL</constant>.</para></listitem>
  87       </varlistentry>
  88
  89       <varlistentry>
  90         <term><constant>-ECHILD</constant></term>
  91
  92         <listitem><para>The bus connection has been created in a different process.</para></listitem>
  93       </varlistentry>
  94
  95       <varlistentry>
  96         <term><constant>-ESTALE</constant></term>
  97
  98         <listitem><para>The bus object the specified bus slot object is associated with has already been freed, and
  99         hence no change in the floating state can be made anymore.</para></listitem>
 100       </varlistentry>
 101     </variablelist>
 102   </refsect1>
 103
 104   <xi:include href="libsystemd-pkgconfig.xml" />
 105
 106   <refsect1>
 107     <title>See Also</title>
 108
 109     <para>
 110       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 111       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 112       <citerefentry><refentrytitle>sd_bus_slot_set_destroy_callback</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 113       <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 114     </para>
 115   </refsect1>
 116
 117 </refentry>