mirror of
https://github.com/systemd/systemd.git
synced 2024-11-23 02:03:37 +08:00
700 lines
36 KiB
XML
700 lines
36 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
|
|
<!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_add_object"
|
|
xmlns:xi="http://www.w3.org/2001/XInclude">
|
|
|
|
<refentryinfo>
|
|
<title>sd_bus_add_object</title>
|
|
<productname>systemd</productname>
|
|
</refentryinfo>
|
|
|
|
<refmeta>
|
|
<refentrytitle>sd_bus_add_object</refentrytitle>
|
|
<manvolnum>3</manvolnum>
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>sd_bus_add_object</refname>
|
|
<refname>sd_bus_add_fallback</refname>
|
|
<refname>sd_bus_add_object_vtable</refname>
|
|
<refname>sd_bus_add_fallback_vtable</refname>
|
|
<refname>sd_bus_add_filter</refname>
|
|
<refname>SD_BUS_VTABLE_CAPABILITY</refname>
|
|
<refname>SD_BUS_VTABLE_START</refname>
|
|
<refname>SD_BUS_VTABLE_END</refname>
|
|
<refname>SD_BUS_METHOD_WITH_NAMES_OFFSET</refname>
|
|
<refname>SD_BUS_METHOD_WITH_NAMES</refname>
|
|
<refname>SD_BUS_METHOD_WITH_OFFSET</refname>
|
|
<refname>SD_BUS_METHOD</refname>
|
|
<refname>SD_BUS_SIGNAL_WITH_NAMES</refname>
|
|
<refname>SD_BUS_SIGNAL</refname>
|
|
<refname>SD_BUS_WRITABLE_PROPERTY</refname>
|
|
<refname>SD_BUS_PROPERTY</refname>
|
|
<refname>SD_BUS_PARAM</refname>
|
|
|
|
<refpurpose>Declare properties and methods for a D-Bus path</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<funcsynopsis>
|
|
<funcsynopsisinfo>#include <systemd/sd-bus-vtable.h></funcsynopsisinfo>
|
|
|
|
<xi:include href="sd_bus_add_match.xml" xpointer="sd_bus_message_handler_t"/>
|
|
|
|
<funcprototype>
|
|
<funcdef>typedef int (*<function>sd_bus_property_get_t</function>)</funcdef>
|
|
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
|
<paramdef>const char *<parameter>path</parameter></paramdef>
|
|
<paramdef>const char *<parameter>interface</parameter></paramdef>
|
|
<paramdef>const char *<parameter>property</parameter></paramdef>
|
|
<paramdef>sd_bus_message *<parameter>reply</parameter></paramdef>
|
|
<paramdef>void *<parameter>userdata</parameter></paramdef>
|
|
<paramdef>sd_bus_error *<parameter>ret_error</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>typedef int (*<function>sd_bus_property_set_t</function>)</funcdef>
|
|
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
|
<paramdef>const char *<parameter>path</parameter></paramdef>
|
|
<paramdef>const char *<parameter>interface</parameter></paramdef>
|
|
<paramdef>const char *<parameter>property</parameter></paramdef>
|
|
<paramdef>sd_bus_message *<parameter>value</parameter></paramdef>
|
|
<paramdef>void *<parameter>userdata</parameter></paramdef>
|
|
<paramdef>sd_bus_error *<parameter>ret_error</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>typedef int (*<function>sd_bus_object_find_t</function>)</funcdef>
|
|
<paramdef>const char *<parameter>path</parameter></paramdef>
|
|
<paramdef>const char *<parameter>interface</parameter></paramdef>
|
|
<paramdef>void *<parameter>userdata</parameter></paramdef>
|
|
<paramdef>void **<parameter>ret_found</parameter></paramdef>
|
|
<paramdef>sd_bus_error *<parameter>ret_error</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_bus_add_object</function></funcdef>
|
|
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
|
<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
|
|
<paramdef>const char *<parameter>path</parameter></paramdef>
|
|
<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
|
|
<paramdef>void *<parameter>userdata</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_bus_add_fallback</function></funcdef>
|
|
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
|
<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
|
|
<paramdef>const char *<parameter>path</parameter></paramdef>
|
|
<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
|
|
<paramdef>void *<parameter>userdata</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_bus_add_object_vtable</function></funcdef>
|
|
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
|
<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
|
|
<paramdef>const char *<parameter>path</parameter></paramdef>
|
|
<paramdef>const char *<parameter>interface</parameter></paramdef>
|
|
<paramdef>const sd_bus_vtable *<parameter>vtable</parameter></paramdef>
|
|
<paramdef>void *<parameter>userdata</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_bus_add_fallback_vtable</function></funcdef>
|
|
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
|
<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
|
|
<paramdef>const char *<parameter>prefix</parameter></paramdef>
|
|
<paramdef>const char *<parameter>interface</parameter></paramdef>
|
|
<paramdef>const sd_bus_vtable *<parameter>vtable</parameter></paramdef>
|
|
<paramdef>sd_bus_object_find_t <parameter>find</parameter></paramdef>
|
|
<paramdef>void *<parameter>userdata</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_bus_add_filter</function></funcdef>
|
|
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
|
<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
|
|
<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
|
|
<paramdef>void *<parameter>userdata</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
|
|
<para>
|
|
<constant>SD_BUS_VTABLE_CAPABILITY(<replaceable>capability</replaceable>)</constant>
|
|
</para>
|
|
|
|
<para>
|
|
<constant>SD_BUS_VTABLE_START(<replaceable>flags</replaceable>)</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_VTABLE_END</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_METHOD_WITH_ARGS_OFFSET(<replaceable>member</replaceable>,
|
|
<replaceable>args</replaceable>,
|
|
<replaceable>result</replaceable>,
|
|
<replaceable>handler</replaceable>,
|
|
<replaceable>offset</replaceable>,
|
|
<replaceable>flags</replaceable>)
|
|
</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_METHOD_WITH_ARGS(<replaceable>member</replaceable>,
|
|
<replaceable>args</replaceable>,
|
|
<replaceable>result</replaceable>,
|
|
<replaceable>handler</replaceable>,
|
|
<replaceable>flags</replaceable>)
|
|
</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_METHOD_WITH_NAMES_OFFSET(<replaceable>member</replaceable>,
|
|
<replaceable>signature</replaceable>,
|
|
<replaceable>in_names</replaceable>,
|
|
<replaceable>result</replaceable>,
|
|
<replaceable>out_names</replaceable>,
|
|
<replaceable>handler</replaceable>,
|
|
<replaceable>offset</replaceable>,
|
|
<replaceable>flags</replaceable>)
|
|
</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_METHOD_WITH_NAMES(<replaceable>member</replaceable>,
|
|
<replaceable>signature</replaceable>,
|
|
<replaceable>in_names</replaceable>,
|
|
<replaceable>result</replaceable>,
|
|
<replaceable>out_names</replaceable>,
|
|
<replaceable>handler</replaceable>,
|
|
<replaceable>flags</replaceable>)
|
|
</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_METHOD_WITH_OFFSET(<replaceable>member</replaceable>,
|
|
<replaceable>signature</replaceable>,
|
|
<replaceable>result</replaceable>,
|
|
<replaceable>handler</replaceable>,
|
|
<replaceable>offset</replaceable>,
|
|
<replaceable>flags</replaceable>)
|
|
</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_METHOD(<replaceable>member</replaceable>,
|
|
<replaceable>signature</replaceable>,
|
|
<replaceable>result</replaceable>,
|
|
<replaceable>handler</replaceable>,
|
|
<replaceable>flags</replaceable>)
|
|
</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_SIGNAL_WITH_ARGS(<replaceable>member</replaceable>,
|
|
<replaceable>args</replaceable>,
|
|
<replaceable>flags</replaceable>)
|
|
</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_SIGNAL_WITH_NAMES(<replaceable>member</replaceable>,
|
|
<replaceable>signature</replaceable>,
|
|
<replaceable>names</replaceable>,
|
|
<replaceable>flags</replaceable>)
|
|
</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_SIGNAL(<replaceable>member</replaceable>,
|
|
<replaceable>signature</replaceable>,
|
|
<replaceable>flags</replaceable>)
|
|
</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_WRITABLE_PROPERTY(<replaceable>member</replaceable>,
|
|
<replaceable>signature</replaceable>,
|
|
<replaceable>get</replaceable>,
|
|
<replaceable>set</replaceable>,
|
|
<replaceable>offset</replaceable>,
|
|
<replaceable>flags</replaceable>)
|
|
</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_PROPERTY(<replaceable>member</replaceable>,
|
|
<replaceable>signature</replaceable>,
|
|
<replaceable>get</replaceable>,
|
|
<replaceable>offset</replaceable>,
|
|
<replaceable>flags</replaceable>)
|
|
</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_PARAM(<replaceable>name</replaceable>)</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_ARGS(<replaceable>...</replaceable>)</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_RESULT(<replaceable>...</replaceable>)</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_NO_ARGS</constant>
|
|
</para>
|
|
<para>
|
|
<constant>SD_BUS_NO_RESULT</constant>
|
|
</para>
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1>
|
|
<title>Description</title>
|
|
|
|
<para><function>sd_bus_add_object_vtable()</function> is used to declare attributes for the
|
|
object path <parameter>path</parameter> connected to the bus connection
|
|
<parameter>bus</parameter> under the interface <parameter>interface</parameter>. The table
|
|
<parameter>vtable</parameter> may contain property declarations using
|
|
<constant>SD_BUS_PROPERTY()</constant> or <constant>SD_BUS_WRITABLE_PROPERTY()</constant>,
|
|
method declarations using <constant>SD_BUS_METHOD()</constant>,
|
|
<constant>SD_BUS_METHOD_WITH_NAMES()</constant>,
|
|
<constant>SD_BUS_METHOD_WITH_OFFSET()</constant>, or
|
|
<constant>SD_BUS_METHOD_WITH_NAMES_OFFSET()</constant>, and signal declarations using
|
|
<constant>SD_BUS_SIGNAL_WITH_NAMES()</constant> or <constant>SD_BUS_SIGNAL()</constant>, see
|
|
below. The <replaceable>userdata</replaceable> parameter contains a pointer that will be passed
|
|
to various callback functions. It may be specified as <constant>NULL</constant> if no value is
|
|
necessary. An interface can have any number of vtables attached to it.</para>
|
|
|
|
<para><function>sd_bus_add_fallback_vtable()</function> is similar to
|
|
<function>sd_bus_add_object_vtable()</function>, but is used to register "fallback" attributes.
|
|
When looking for an attribute declaration, bus object paths registered with
|
|
<function>sd_bus_add_object_vtable()</function> are checked first. If no match is found, the
|
|
fallback vtables are checked for each prefix of the bus object path, i.e. with the last
|
|
slash-separated components successively removed. This allows the vtable to be used for an
|
|
arbitrary number of dynamically created objects.</para>
|
|
|
|
<para>Parameter <replaceable>find</replaceable> is a function which is used to locate the target
|
|
object based on the bus object path <replaceable>path</replaceable>. It must return
|
|
<constant>1</constant> and set the <parameter>ret_found</parameter> output parameter if the
|
|
object is found, return <constant>0</constant> if the object was not found, and return a
|
|
negative errno-style error code or initialize the error structure
|
|
<replaceable>ret_error</replaceable> on error. The pointer passed in
|
|
<parameter>ret_found</parameter> will be used as the <parameter>userdata</parameter> parameter
|
|
for the callback functions (offset by the <parameter>offset</parameter> offsets as specified in
|
|
the vtable entries).</para>
|
|
|
|
<para><function>sd_bus_add_object()</function> attaches a callback directly to the object path
|
|
<parameter>path</parameter>. An object path can have any number of callbacks attached to it.
|
|
Each callback is prepended to the list of callbacks which are always called in order.
|
|
<function>sd_bus_add_fallback()</function> is similar to
|
|
<function>sd_bus_add_object()</function> but applies to fallback paths instead.</para>
|
|
|
|
<para><function>sd_bus_add_filter()</function> installs a callback that is invoked for each
|
|
incoming D-Bus message. Filters can be used to handle logic common to all messages received by
|
|
a service (e.g. authentication or authorization).</para>
|
|
|
|
<para>When a request is received, any associated callbacks are called sequentially until a
|
|
callback returns a non-zero integer. Return zero from a callback to give other callbacks the
|
|
chance to process the request. Callbacks are called in the following order: first, global
|
|
callbacks installed with <function>sd_bus_add_filter()</function> are called. Second, callbacks
|
|
attached directly to the request object path are called, followed by any D-Bus method callbacks
|
|
attached to the request object path, interface and member. Finally, the property callbacks
|
|
attached to the request object path, interface and member are called. If the final callback
|
|
returns zero, an error reply is sent back to the caller indicating no matching object for the
|
|
request was found.</para>
|
|
|
|
<para>Note that you can return a positive integer from a <parameter>method</parameter> callback without
|
|
immediately sending a reply. This informs sd-bus this callback will take responsibility for
|
|
replying to the request without forcing the callback to produce a reply immediately. This allows
|
|
a callback to perform any number of asynchronous operations required to construct a reply.
|
|
However, if producing a reply takes too long, the method call will time out at the caller. This is
|
|
only available to methods and not properties.</para>
|
|
|
|
<para>If a callback was invoked to handle a request that expects a reply and the callback
|
|
returns a negative value, the value is interpreted as a negative errno-style error code and sent
|
|
back to the caller as a D-Bus error as if
|
|
<citerefentry><refentrytitle>sd_bus_reply_method_errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
was called. Additionally, all callbacks take a <structname>sd_bus_error</structname> output
|
|
parameter that can be used to provide more detailed error information. If
|
|
<parameter>ret_error</parameter> is set when the callback finishes, the corresponding D-Bus
|
|
error is sent back to the caller as if
|
|
<citerefentry><refentrytitle>sd_bus_reply_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
was called. Any error stored in <parameter>ret_error</parameter> takes priority over any
|
|
negative values returned by the same callback when determining which error to send back to
|
|
the caller. Use
|
|
<citerefentry><refentrytitle>sd_bus_error_set</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
or one of its variants to set <parameter>ret_error</parameter> and return a negative integer
|
|
from a callback with a single function call. To send an error reply after a callback has already
|
|
finished, use
|
|
<citerefentry><refentrytitle>sd_bus_reply_method_errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
or one of its variants.</para>
|
|
|
|
<para>For all functions, a match slot is created internally. If the output parameter
|
|
<replaceable>slot</replaceable> is <constant>NULL</constant>, a "floating" slot object is
|
|
created, see
|
|
<citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
|
Otherwise, a pointer to the slot object is returned. In that case, the reference to the slot
|
|
object should be dropped when the vtable is not needed anymore, see
|
|
<citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
|
</para>
|
|
|
|
<refsect2>
|
|
<title>The <structname>sd_bus_vtable</structname> array</title>
|
|
|
|
<para>The array consists of the structures of type <structname>sd_bus_vtable</structname>, but it
|
|
should never be filled in manually, but through one of the following macros:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_VTABLE_START(<replaceable>flags</replaceable>)</constant></term>
|
|
<term><constant>SD_BUS_VTABLE_END</constant></term>
|
|
|
|
<listitem><para>Those must always be the first and last element. The
|
|
<replaceable>flags</replaceable> parameter can be used to set attributes that apply to the whole
|
|
array; see the "Flags" section below.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_METHOD_WITH_ARGS_OFFSET()</constant></term>
|
|
<term><constant>SD_BUS_METHOD_WITH_ARGS()</constant></term>
|
|
|
|
<listitem><para>Declare a D-Bus method with the name <replaceable>member</replaceable>,
|
|
arguments <replaceable>args</replaceable> and result <replaceable>result</replaceable>.
|
|
<replaceable>args</replaceable> expects a sequence of argument type/name pairs wrapped in the
|
|
<constant>SD_BUS_ARGS()</constant> macro. The elements at even indices in this list describe the
|
|
types of the method's arguments. The method's parameter signature is the concatenation of all the
|
|
string literals at even indices in <replaceable>args</replaceable>. If a method has no parameters,
|
|
pass <constant>SD_BUS_NO_ARGS</constant> to <replaceable>args</replaceable>. The elements at uneven
|
|
indices describe the names of the method's arguments. <replaceable>result</replaceable> expects a
|
|
sequence of type/name pairs wrapped in the <constant>SD_BUS_RESULT()</constant> macro in the same
|
|
format as <constant>SD_BUS_ARGS()</constant>. The method's result signature is the concatenation of
|
|
all the string literals at even indices in <replaceable>result</replaceable>. If a method has no
|
|
result, pass <constant>SD_BUS_NO_RESULT</constant> to <replaceable>result</replaceable>. Note that
|
|
argument types are expected to be quoted string literals and argument names are expected to be
|
|
unquoted string literals. See below for a complete example.</para>
|
|
|
|
<para>The handler function <replaceable>handler</replaceable> must be of type
|
|
<function>sd_bus_message_handler_t</function>. It will be called to handle the incoming messages
|
|
that call this method. It receives a pointer that is the <replaceable>userdata</replaceable>
|
|
parameter passed to the registration function offset by <replaceable>offset</replaceable> bytes.
|
|
This may be used to pass pointers to different fields in the same data structure to different
|
|
methods in the same vtable. To send a reply from <parameter>handler</parameter>, call
|
|
<citerefentry><refentrytitle>sd_bus_reply_method_return</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
with the message the callback was invoked with. Parameter <replaceable>flags</replaceable> is a
|
|
combination of flags, see below.</para>
|
|
|
|
<para><constant>SD_BUS_METHOD_WITH_ARGS()</constant> is a shorthand for calling
|
|
<constant>SD_BUS_METHOD_WITH_ARGS_OFFSET()</constant> with an offset of zero.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_METHOD_WITH_NAMES_OFFSET()</constant></term>
|
|
<term><constant>SD_BUS_METHOD_WITH_NAMES()</constant></term>
|
|
<term><constant>SD_BUS_METHOD_WITH_OFFSET()</constant></term>
|
|
<term><constant>SD_BUS_METHOD()</constant></term>
|
|
|
|
<listitem><para>Declare a D-Bus method with the name <replaceable>member</replaceable>,
|
|
parameter signature <replaceable>signature</replaceable>, result signature
|
|
<replaceable>result</replaceable>. Parameters <replaceable>in_names</replaceable> and
|
|
<replaceable>out_names</replaceable> specify the argument names of the input and output
|
|
arguments in the function signature. <replaceable>in_names</replaceable> and
|
|
<replaceable>out_names</replaceable> should be created using the
|
|
<constant>SD_BUS_PARAM()</constant> macro, see below. In all other regards, this macro behaves
|
|
exactly the same as <constant>SD_BUS_METHOD_WITH_ARGS_OFFSET()</constant>.</para>
|
|
|
|
<para><constant>SD_BUS_METHOD_WITH_NAMES()</constant>,
|
|
<constant>SD_BUS_METHOD_WITH_OFFSET()</constant>, and <constant>SD_BUS_METHOD()</constant>
|
|
are variants which specify zero offset (<replaceable>userdata</replaceable> parameter is
|
|
passed with no change), leave the names unset (i.e. no parameter names), or both.</para>
|
|
|
|
<para>Prefer using <constant>SD_BUS_METHOD_WITH_ARGS_OFFSET()</constant> and
|
|
<constant>SD_BUS_METHOD_WITH_ARGS()</constant> over these macros as they allow specifying argument
|
|
types and names next to each other which is less error-prone than first specifying all argument
|
|
types followed by specifying all argument names.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_SIGNAL_WITH_ARGS()</constant></term>
|
|
|
|
<listitem><para>Declare a D-Bus signal with the name <replaceable>member</replaceable> and
|
|
arguments <replaceable>args</replaceable>. <replaceable>args</replaceable> expects a sequence of
|
|
argument type/name pairs wrapped in the <constant>SD_BUS_ARGS()</constant> macro. The elements at
|
|
even indices in this list describe the types of the signal's arguments. The signal's parameter
|
|
signature is the concatenation of all the string literals at even indices in
|
|
<replaceable>args</replaceable>. If a signal has no parameters, pass
|
|
<constant>SD_BUS_NO_ARGS</constant> to <replaceable>args</replaceable>. The elements at uneven
|
|
indices describe the names of the signal's arguments. Parameter <replaceable>flags</replaceable> is
|
|
a combination of flags. See below for a complete example.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_SIGNAL_WITH_NAMES()</constant></term>
|
|
<term><constant>SD_BUS_SIGNAL()</constant></term>
|
|
|
|
<listitem><para>Declare a D-Bus signal with the name <replaceable>member</replaceable>,
|
|
parameter signature <replaceable>signature</replaceable>, and argument names
|
|
<replaceable>names</replaceable>. <replaceable>names</replaceable> should be
|
|
created using the <constant>SD_BUS_PARAM()</constant> macro, see below.
|
|
Parameter <replaceable>flags</replaceable> is a combination of flags, see below.
|
|
</para>
|
|
|
|
<para><constant>SD_BUS_SIGNAL()</constant> is equivalent to
|
|
<constant>SD_BUS_SIGNAL_WITH_NAMES()</constant> with the <replaceable>names</replaceable> parameter
|
|
unset (i.e. no parameter names).</para>
|
|
|
|
<para>Prefer using <constant>SD_BUS_SIGNAL_WITH_ARGS()</constant> over these macros as it allows
|
|
specifying argument types and names next to each other which is less error-prone than first
|
|
specifying all argument types followed by specifying all argument names.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_WRITABLE_PROPERTY()</constant></term>
|
|
<term><constant>SD_BUS_PROPERTY()</constant></term>
|
|
|
|
<listitem><para>Declare a D-Bus property with the name <replaceable>member</replaceable>
|
|
and value signature <replaceable>signature</replaceable>. Parameters
|
|
<replaceable>get</replaceable> and <replaceable>set</replaceable> are the getter and
|
|
setter methods. They are called with a pointer that is the
|
|
<replaceable>userdata</replaceable> parameter passed to the registration function offset
|
|
by <replaceable>offset</replaceable> bytes. This may be used pass pointers to different
|
|
fields in the same data structure to different setters and getters in the same vtable.
|
|
Parameter <replaceable>flags</replaceable> is a combination of flags, see below.</para>
|
|
|
|
<para>The setter and getter methods may be omitted (specified as
|
|
<constant>NULL</constant>), if the property is one of the basic types or
|
|
<literal>as</literal> in case of read-only properties. In those cases, the
|
|
<replaceable>userdata</replaceable> and <replaceable>offset</replaceable> parameters must
|
|
together point to a valid variable of the corresponding type. A default setter and getter
|
|
will be provided, which simply copy the argument between this variable and the message.
|
|
</para>
|
|
|
|
<para><constant>SD_BUS_PROPERTY()</constant> is used to define a read-only property.
|
|
</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_PARAM()</constant></term>
|
|
<listitem><para>Parameter names should be wrapped in this macro, see the example below.
|
|
</para></listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect2>
|
|
|
|
<refsect2>
|
|
<title>Flags</title>
|
|
|
|
<para>The <replaceable>flags</replaceable> parameter is used to specify a combination of
|
|
<ulink url="https://dbus.freedesktop.org/doc/dbus-specification.html#introspection-format">D-Bus annotations</ulink>.
|
|
</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_VTABLE_DEPRECATED</constant></term>
|
|
|
|
<listitem><para>Mark this vtable entry as deprecated using the
|
|
<constant>org.freedesktop.DBus.Deprecated</constant> annotation in introspection data. If
|
|
specified for <constant>SD_BUS_VTABLE_START()</constant>, the annotation is applied to the
|
|
enclosing interface.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_VTABLE_HIDDEN</constant></term>
|
|
|
|
<listitem><para>Make this vtable entry hidden. It will not be shown in introspection data.
|
|
If specified for <constant>SD_BUS_VTABLE_START()</constant>, all entries in the array are
|
|
hidden.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_VTABLE_METHOD_NO_REPLY</constant></term>
|
|
|
|
<listitem><para>Mark this vtable entry as a method that will not return a reply using the
|
|
<constant>org.freedesktop.DBus.Method.NoReply</constant> annotation in introspection data.
|
|
</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_VTABLE_PROPERTY_CONST</constant></term>
|
|
<term><constant>SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE</constant></term>
|
|
<term><constant>SD_BUS_VTABLE_PROPERTY_EMITS_INVALIDATION</constant></term>
|
|
|
|
<listitem><para>Those three flags correspond to different values of the
|
|
<constant>org.freedesktop.DBus.Property.EmitsChangedSignal</constant> annotation, which
|
|
specifies whether the
|
|
<constant>org.freedesktop.DBus.Properties.PropertiesChanged</constant> signal is emitted
|
|
whenever the property changes. <constant>SD_BUS_VTABLE_PROPERTY_CONST</constant>
|
|
corresponds to <constant>const</constant> and means that the property never changes during
|
|
the lifetime of the object it belongs to, so no signal needs to be emitted.
|
|
<constant>SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE</constant> corresponds to
|
|
<constant>true</constant> and means that the signal is emitted.
|
|
<constant>SD_BUS_VTABLE_PROPERTY_EMITS_INVALIDATION</constant> corresponds to
|
|
<constant>invalidates</constant> and means that the signal is emitted, but the value is
|
|
not included in the signal.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_VTABLE_PROPERTY_EXPLICIT</constant></term>
|
|
|
|
<listitem><para>Mark this vtable property entry as requiring explicit request to for the
|
|
value to be shown (generally because the value is large or slow to calculate). This entry
|
|
cannot be combined with <constant>SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE</constant>, and will
|
|
not be shown in property listings by default (e.g. <command>busctl introspect</command>).
|
|
This corresponds to the <constant>org.freedesktop.systemd1.Explicit</constant> annotation
|
|
in introspection data.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_VTABLE_SENSITIVE</constant></term>
|
|
|
|
<listitem><para>Mark this vtable method entry as processing sensitive data. When set,
|
|
incoming method call messages and their outgoing reply messages are marked as sensitive using
|
|
<citerefentry><refentrytitle>sd_bus_message_sensitive</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
so that they are erased from memory when freed.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_VTABLE_ABSOLUTE_OFFSET</constant></term>
|
|
|
|
<listitem><para>Mark this vtable method or property entry so that the user data pointer passed to
|
|
its associated handler functions is determined slightly differently: instead of adding the offset
|
|
parameter of the entry to the user data pointer specified during vtable registration, the offset is
|
|
passed directly, converted to a pointer, without taking the user data pointer specified during
|
|
vtable registration into account.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_VTABLE_CAPABILITY(<replaceable>capability</replaceable>)</constant></term>
|
|
|
|
<listitem><para>Access to this vtable entry will be allowed if the calling process has the
|
|
capability <replaceable>capability</replaceable>, as described in
|
|
<citerefentry><refentrytitle>sd_bus_query_sender_privilege</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
|
If used for <constant>SD_BUS_VTABLE_START()</constant>, provides a default for all entries in the
|
|
array. If not specified, either for an individual entry or the whole array,
|
|
<constant>CAP_SYS_ADMIN</constant> is checked by default. See <citerefentry
|
|
project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
|
|
for information about capabilities.</para>
|
|
|
|
<para>Note that vtable entries may be marked as unprivileged and the whole bus may be marked as
|
|
trusted, see the discussion of <constant>SD_BUS_VTABLE_UNPRIVILEGED</constant> below.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>SD_BUS_VTABLE_UNPRIVILEGED</constant></term>
|
|
|
|
<listitem><para>Mark this vtable entry as unprivileged. Access to privileged entries is limited to
|
|
users with appropriate capabilities as described above. In practice many vtable entries are marked
|
|
as unprivileged, and either are open to everyone, or the decision whether to allow access is taken
|
|
later, e.g. by delegating to <ulink
|
|
url="https://www.freedesktop.org/software/polkit/docs/latest/">polkit</ulink>.</para>
|
|
|
|
<para>The whole bus may be marked as trusted, in which case annotations at the entry level are
|
|
ignored, see
|
|
<citerefentry><refentrytitle>sd_bus_set_trusted</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
|
</para>
|
|
|
|
<para>When <emphasis>not</emphasis> specified, the
|
|
<constant>org.freedesktop.systemd1.Privileged</constant> annotation with value
|
|
<literal>true</literal> will be shown in introspection data.</para>
|
|
|
|
<para>Note that this page describes checks implemented in the D-Bus client. The D-Bus server has an
|
|
additional policy that may permit or deny connections, see
|
|
"CONFIGURATION FILE" in
|
|
<citerefentry project='man-pages'><refentrytitle>dbus-daemon</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
|
|
</para></listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect2>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Examples</title>
|
|
|
|
<example>
|
|
<title>Create a simple listener on the bus</title>
|
|
|
|
<programlisting><xi:include href="vtable-example.c" parse="text" /></programlisting>
|
|
|
|
<para>This creates a simple client on the bus (the user bus, when run as normal user). We may
|
|
use the D-Bus <constant>org.freedesktop.DBus.Introspectable.Introspect</constant> call to
|
|
acquire the XML description of the interface:</para>
|
|
|
|
<programlisting><xi:include href="vtable-example.xml" parse="text" /></programlisting>
|
|
</example>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Return Value</title>
|
|
|
|
<para>On success, <function>sd_bus_add_object_vtable()</function> and
|
|
<function>sd_bus_add_fallback_vtable()</function> return a non-negative integer. On
|
|
failure, they return a negative errno-style error code.</para>
|
|
|
|
<refsect2>
|
|
<title>Errors</title>
|
|
|
|
<para>Returned errors may indicate the following problems:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><constant>-EINVAL</constant></term>
|
|
|
|
<listitem><para>One of the required parameters is <constant>NULL</constant> or invalid. A
|
|
reserved D-Bus interface was passed as the <replaceable>interface</replaceable> parameter.
|
|
</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-ENOPKG</constant></term>
|
|
|
|
<listitem><para>The bus cannot be resolved.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-ECHILD</constant></term>
|
|
|
|
<listitem><para>The bus was created in a different process, library or module instance.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-ENOMEM</constant></term>
|
|
|
|
<listitem><para>Memory allocation failed.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-EPROTOTYPE</constant></term>
|
|
|
|
<listitem><para><function>sd_bus_add_object_vtable()</function> and
|
|
<function>sd_bus_add_fallback_vtable()</function> have been both called for the same bus
|
|
object path, which is not allowed.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-EEXIST</constant></term>
|
|
|
|
<listitem><para>This vtable has already been registered for this
|
|
<replaceable>interface</replaceable> and <replaceable>path</replaceable>.</para></listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect2>
|
|
</refsect1>
|
|
|
|
<xi:include href="libsystemd-pkgconfig.xml" />
|
|
|
|
<refsect1>
|
|
<title>History</title>
|
|
<para><function>sd_bus_property_get_t()</function>,
|
|
<function>sd_bus_property_set_t()</function>,
|
|
<function>sd_bus_object_find_t()</function>,
|
|
<function>sd_bus_add_object()</function>,
|
|
<function>sd_bus_add_fallback()</function>,
|
|
<function>sd_bus_add_object_vtable()</function>,
|
|
<function>sd_bus_add_fallback_vtable()</function>, and
|
|
<function>sd_bus_add_filter()</function> were added in version 221.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>See Also</title>
|
|
|
|
<para><simplelist type="inline">
|
|
<member><citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>busctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>sd_bus_emit_properties_changed</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>sd_bus_emit_object_added</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
|
|
</simplelist></para>
|
|
</refsect1>
|
|
</refentry>
|