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1 | <?xml version='1.0'?> <!--*-nxml-*--> |
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 | ||
9b62e232 | 6 | <refentry id="sd_bus_add_object" |
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7 | xmlns:xi="http://www.w3.org/2001/XInclude"> |
8 | ||
9 | <refentryinfo> | |
9b62e232 | 10 | <title>sd_bus_add_object</title> |
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11 | <productname>systemd</productname> |
12 | </refentryinfo> | |
13 | ||
14 | <refmeta> | |
9b62e232 | 15 | <refentrytitle>sd_bus_add_object</refentrytitle> |
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16 | <manvolnum>3</manvolnum> |
17 | </refmeta> | |
18 | ||
19 | <refnamediv> | |
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20 | <refname>sd_bus_add_object</refname> |
21 | <refname>sd_bus_add_fallback</refname> | |
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22 | <refname>sd_bus_add_object_vtable</refname> |
23 | <refname>sd_bus_add_fallback_vtable</refname> | |
3841fa79 | 24 | <refname>sd_bus_add_filter</refname> |
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25 | <refname>SD_BUS_VTABLE_START</refname> |
26 | <refname>SD_BUS_VTABLE_END</refname> | |
27 | <refname>SD_BUS_METHOD_WITH_NAMES_OFFSET</refname> | |
28 | <refname>SD_BUS_METHOD_WITH_NAMES</refname> | |
29 | <refname>SD_BUS_METHOD_WITH_OFFSET</refname> | |
30 | <refname>SD_BUS_METHOD</refname> | |
31 | <refname>SD_BUS_SIGNAL_WITH_NAMES</refname> | |
32 | <refname>SD_BUS_SIGNAL</refname> | |
33 | <refname>SD_BUS_WRITABLE_PROPERTY</refname> | |
34 | <refname>SD_BUS_PROPERTY</refname> | |
35 | <refname>SD_BUS_PARAM</refname> | |
36 | ||
37 | <refpurpose>Declare properties and methods for a D-Bus path</refpurpose> | |
38 | </refnamediv> | |
39 | ||
40 | <refsynopsisdiv> | |
41 | <funcsynopsis> | |
42 | <funcsynopsisinfo>#include <systemd/sd-bus-vtable.h></funcsynopsisinfo> | |
43 | ||
44 | <funcprototype> | |
45 | <funcdef>typedef int (*<function>sd_bus_message_handler_t</function>)</funcdef> | |
46 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
47 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
48 | <paramdef>sd_bus_error *<parameter>ret_error</parameter></paramdef> | |
49 | </funcprototype> | |
50 | ||
51 | <funcprototype> | |
52 | <funcdef>typedef int (*<function>sd_bus_property_get_t</function>)</funcdef> | |
53 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
54 | <paramdef>const char *<parameter>path</parameter></paramdef> | |
55 | <paramdef>const char *<parameter>interface</parameter></paramdef> | |
56 | <paramdef>const char *<parameter>property</parameter></paramdef> | |
57 | <paramdef>sd_bus_message *<parameter>reply</parameter></paramdef> | |
58 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
59 | <paramdef>sd_bus_error *<parameter>ret_error</parameter></paramdef> | |
60 | </funcprototype> | |
61 | ||
62 | <funcprototype> | |
63 | <funcdef>typedef int (*<function>sd_bus_property_set_t</function>)</funcdef> | |
64 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
65 | <paramdef>const char *<parameter>path</parameter></paramdef> | |
66 | <paramdef>const char *<parameter>interface</parameter></paramdef> | |
67 | <paramdef>const char *<parameter>property</parameter></paramdef> | |
68 | <paramdef>sd_bus_message *<parameter>value</parameter></paramdef> | |
69 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
70 | <paramdef>sd_bus_error *<parameter>ret_error</parameter></paramdef> | |
71 | </funcprototype> | |
72 | ||
73 | <funcprototype> | |
74 | <funcdef>typedef int (*<function>sd_bus_object_find_t</function>)</funcdef> | |
75 | <paramdef>const char *<parameter>path</parameter></paramdef> | |
76 | <paramdef>const char *<parameter>interface</parameter></paramdef> | |
77 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
78 | <paramdef>void **<parameter>ret_found</parameter></paramdef> | |
79 | <paramdef>sd_bus_error *<parameter>ret_error</parameter></paramdef> | |
80 | </funcprototype> | |
81 | ||
82 | <funcprototype> | |
9b62e232 | 83 | <funcdef>int <function>sd_bus_add_object</function></funcdef> |
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84 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> |
85 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
86 | <paramdef>const char *<parameter>path</parameter></paramdef> | |
9b62e232 | 87 | <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> |
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88 | <paramdef>void *<parameter>userdata</parameter></paramdef> |
89 | </funcprototype> | |
90 | ||
91 | <funcprototype> | |
9b62e232 | 92 | <funcdef>int <function>sd_bus_add_fallback</function></funcdef> |
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93 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> |
94 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
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95 | <paramdef>const char *<parameter>path</parameter></paramdef> |
96 | <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> | |
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97 | <paramdef>void *<parameter>userdata</parameter></paramdef> |
98 | </funcprototype> | |
99 | ||
fc91667d | 100 | <funcprototype> |
9b62e232 | 101 | <funcdef>int <function>sd_bus_add_object_vtable</function></funcdef> |
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102 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> |
103 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
104 | <paramdef>const char *<parameter>path</parameter></paramdef> | |
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105 | <paramdef>const char *<parameter>interface</parameter></paramdef> |
106 | <paramdef>const sd_bus_vtable *<parameter>vtable</parameter></paramdef> | |
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107 | <paramdef>void *<parameter>userdata</parameter></paramdef> |
108 | </funcprototype> | |
109 | ||
110 | <funcprototype> | |
9b62e232 | 111 | <funcdef>int <function>sd_bus_add_fallback_vtable</function></funcdef> |
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112 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> |
113 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
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114 | <paramdef>const char *<parameter>prefix</parameter></paramdef> |
115 | <paramdef>const char *<parameter>interface</parameter></paramdef> | |
116 | <paramdef>const sd_bus_vtable *<parameter>vtable</parameter></paramdef> | |
117 | <paramdef>sd_bus_object_find_t <parameter>find</parameter></paramdef> | |
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118 | <paramdef>void *<parameter>userdata</parameter></paramdef> |
119 | </funcprototype> | |
120 | ||
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121 | <funcprototype> |
122 | <funcdef>int <function>sd_bus_add_filter</function></funcdef> | |
123 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
124 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
125 | <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> | |
126 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
127 | </funcprototype> | |
128 | ||
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129 | <para> |
130 | <constant>SD_BUS_VTABLE_START(<replaceable>flags</replaceable>)</constant> | |
131 | </para> | |
132 | <para> | |
133 | <constant>SD_BUS_VTABLE_END</constant> | |
134 | </para> | |
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135 | <para> |
136 | <constant>SD_BUS_METHOD_WITH_ARGS_OFFSET( | |
137 | <replaceable>member</replaceable>, | |
138 | <replaceable>args</replaceable>, | |
139 | <replaceable>result</replaceable>, | |
140 | <replaceable>handler</replaceable>, | |
141 | <replaceable>offset</replaceable>, | |
142 | <replaceable>flags</replaceable>) | |
143 | </constant> | |
144 | </para> | |
145 | <para> | |
146 | <constant>SD_BUS_METHOD_WITH_ARGS( | |
147 | <replaceable>member</replaceable>, | |
148 | <replaceable>args</replaceable>, | |
149 | <replaceable>result</replaceable>, | |
150 | <replaceable>handler</replaceable>, | |
151 | <replaceable>flags</replaceable>) | |
152 | </constant> | |
153 | </para> | |
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154 | <para> |
155 | <constant>SD_BUS_METHOD_WITH_NAMES_OFFSET( | |
156 | <replaceable>member</replaceable>, | |
157 | <replaceable>signature</replaceable>, | |
158 | <replaceable>in_names</replaceable>, | |
159 | <replaceable>result</replaceable>, | |
160 | <replaceable>out_names</replaceable>, | |
161 | <replaceable>handler</replaceable>, | |
162 | <replaceable>offset</replaceable>, | |
163 | <replaceable>flags</replaceable>) | |
164 | </constant> | |
165 | </para> | |
166 | <para> | |
167 | <constant>SD_BUS_METHOD_WITH_NAMES( | |
168 | <replaceable>member</replaceable>, | |
169 | <replaceable>signature</replaceable>, | |
170 | <replaceable>in_names</replaceable>, | |
171 | <replaceable>result</replaceable>, | |
172 | <replaceable>out_names</replaceable>, | |
173 | <replaceable>handler</replaceable>, | |
174 | <replaceable>flags</replaceable>) | |
175 | </constant> | |
176 | </para> | |
177 | <para> | |
178 | <constant>SD_BUS_METHOD_WITH_OFFSET( | |
179 | <replaceable>member</replaceable>, | |
180 | <replaceable>signature</replaceable>, | |
181 | <replaceable>result</replaceable>, | |
182 | <replaceable>handler</replaceable>, | |
183 | <replaceable>offset</replaceable>, | |
184 | <replaceable>flags</replaceable>) | |
185 | </constant> | |
186 | </para> | |
187 | <para> | |
188 | <constant>SD_BUS_METHOD( | |
189 | <replaceable>member</replaceable>, | |
190 | <replaceable>signature</replaceable>, | |
191 | <replaceable>result</replaceable>, | |
192 | <replaceable>handler</replaceable>, | |
193 | <replaceable>flags</replaceable>) | |
194 | </constant> | |
195 | </para> | |
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196 | <para> |
197 | <constant>SD_BUS_SIGNAL_WITH_ARGS( | |
198 | <replaceable>member</replaceable>, | |
199 | <replaceable>args</replaceable>, | |
200 | <replaceable>flags</replaceable>) | |
201 | </constant> | |
202 | </para> | |
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203 | <para> |
204 | <constant>SD_BUS_SIGNAL_WITH_NAMES( | |
205 | <replaceable>member</replaceable>, | |
206 | <replaceable>signature</replaceable>, | |
207 | <replaceable>names</replaceable>, | |
208 | <replaceable>flags</replaceable>) | |
209 | </constant> | |
210 | </para> | |
211 | <para> | |
212 | <constant>SD_BUS_SIGNAL( | |
213 | <replaceable>member</replaceable>, | |
214 | <replaceable>signature</replaceable>, | |
215 | <replaceable>flags</replaceable>) | |
216 | </constant> | |
217 | </para> | |
218 | <para> | |
219 | <constant>SD_BUS_WRITABLE_PROPERTY( | |
220 | <replaceable>member</replaceable>, | |
221 | <replaceable>signature</replaceable>, | |
222 | <replaceable>get</replaceable>, | |
223 | <replaceable>set</replaceable>, | |
224 | <replaceable>offset</replaceable>, | |
225 | <replaceable>flags</replaceable>) | |
226 | </constant> | |
227 | </para> | |
228 | <para> | |
229 | <constant>SD_BUS_PROPERTY( | |
230 | <replaceable>member</replaceable>, | |
231 | <replaceable>signature</replaceable>, | |
232 | <replaceable>get</replaceable>, | |
233 | <replaceable>offset</replaceable>, | |
234 | <replaceable>flags</replaceable>) | |
235 | </constant> | |
236 | </para> | |
237 | <para> | |
238 | <constant>SD_BUS_PARAM(<replaceable>name</replaceable>)</constant> | |
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239 | <constant>SD_BUS_ARGS(<replaceable>...</replaceable>)</constant> |
240 | <constant>SD_BUS_RESULT(<replaceable>...</replaceable>)</constant> | |
241 | <constant>SD_BUS_NO_ARGS</constant> | |
242 | <constant>SD_BUS_NO_RESULT</constant> | |
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243 | </para> |
244 | </funcsynopsis> | |
245 | </refsynopsisdiv> | |
246 | ||
247 | <refsect1> | |
248 | <title>Description</title> | |
249 | ||
6ba8071c | 250 | <para><function>sd_bus_add_object_vtable()</function> is used to declare attributes for the |
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251 | object path <parameter>path</parameter> connected to the bus connection |
252 | <parameter>bus</parameter> under the interface <parameter>interface</parameter>. The table | |
253 | <parameter>vtable</parameter> may contain property declarations using | |
254 | <constant>SD_BUS_PROPERTY()</constant> or <constant>SD_BUS_WRITABLE_PROPERTY()</constant>, | |
255 | method declarations using <constant>SD_BUS_METHOD()</constant>, | |
256 | <constant>SD_BUS_METHOD_WITH_NAMES()</constant>, | |
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257 | <constant>SD_BUS_METHOD_WITH_OFFSET()</constant>, or |
258 | <constant>SD_BUS_METHOD_WITH_NAMES_OFFSET()</constant>, and signal declarations using | |
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259 | <constant>SD_BUS_SIGNAL_WITH_NAMES()</constant> or <constant>SD_BUS_SIGNAL()</constant>, see |
260 | below. The <replaceable>userdata</replaceable> parameter contains a pointer that will be passed | |
261 | to various callback functions. It may be specified as <constant>NULL</constant> if no value is | |
fc91667d | 262 | necessary. An interface can have any number of vtables attached to it.</para> |
afb9c0c9 | 263 | |
12880d14 | 264 | <para><function>sd_bus_add_fallback_vtable()</function> is similar to |
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265 | <function>sd_bus_add_object_vtable()</function>, but is used to register "fallback" attributes. |
266 | When looking for an attribute declaration, bus object paths registered with | |
267 | <function>sd_bus_add_object_vtable()</function> are checked first. If no match is found, the | |
268 | fallback vtables are checked for each prefix of the bus object path, i.e. with the last | |
269 | slash-separated components successively removed. This allows the vtable to be used for an | |
270 | arbitrary number of dynamically created objects.</para> | |
271 | ||
272 | <para>Parameter <replaceable>find</replaceable> is a function which is used to locate the target | |
273 | object based on the bus object path <replaceable>path</replaceable>. It must return | |
274 | <constant>1</constant> and set the <parameter>ret_found</parameter> output parameter if the | |
275 | object is found, return <constant>0</constant> if the object was not found, and return a | |
276 | negative errno-style error code or initialize the error structure | |
277 | <replaceable>ret_error</replaceable> on error. The pointer passed in | |
278 | <parameter>ret_found</parameter> will be used as the <parameter>userdata</parameter> parameter | |
279 | for the callback functions (offset by the <parameter>offset</parameter> offsets as specified in | |
280 | the vtable entries).</para> | |
afb9c0c9 | 281 | |
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282 | <para><function>sd_bus_add_object()</function> attaches a callback directly to the object path |
283 | <parameter>path</parameter>. An object path can have any number of callbacks attached to it. | |
284 | Each callback is prepended to the list of callbacks which are always called in order. | |
285 | <function>sd_bus_add_fallback()</function> is similar to | |
286 | <function>sd_bus_add_object()</function> but applies to fallback paths instead.</para> | |
287 | ||
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288 | <para><function>sd_bus_add_filter()</function> installs a callback that is invoked for each |
289 | incoming D-Bus message. Filters can be used to handle logic common to all messages received by | |
290 | a service (e.g. authentication or authorization).</para> | |
291 | ||
fc91667d | 292 | <para>When a request is received, any associated callbacks are called sequentially until a |
9b62e232 | 293 | callback returns a non-zero integer. Return zero from a callback to give other callbacks the |
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294 | chance to process the request. Callbacks are called in the following order: first, global |
295 | callbacks installed with <function>sd_bus_add_filter()</function> are called. Second, callbacks | |
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296 | attached directly to the request object path are called, followed by any D-Bus method callbacks |
297 | attached to the request object path, interface and member. Finally, the property callbacks | |
298 | attached to the request object path, interface and member are called. If the final callback | |
299 | returns zero, an error reply is sent back to the caller indicating no matching object for the | |
300 | request was found. Note that you can return a positive integer from a callback without | |
301 | immediately sending a reply. This informs sd-bus this callback will take responsibility for | |
302 | replying to the request without forcing the callback to produce a reply immediately. This allows | |
303 | a callback to perform any number of asynchronous operations required to construct a reply. Note | |
9b62e232 | 304 | that if producing a reply takes too long, the method call will time out at the caller.</para> |
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305 | |
306 | <para>If a callback was invoked to handle a request that expects a reply and the callback | |
307 | returns a negative value, the value is interpreted as a negative errno-style error code and sent | |
308 | back to the caller as a D-Bus error as if | |
309 | <citerefentry><refentrytitle>sd_bus_reply_method_errno</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
310 | was called. Additionally, all callbacks take a <structname>sd_bus_error</structname> output | |
311 | parameter that can be used to provide more detailed error information. If | |
312 | <parameter>ret_error</parameter> is set when the callback finishes, the corresponding D-Bus | |
313 | error is sent back to the caller as if | |
314 | <citerefentry><refentrytitle>sd_bus_reply_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
315 | was called. Any error stored in <parameter>ret_error</parameter> takes priority over any | |
316 | negative values returned by the same callback when determining which error to send back to | |
317 | the caller. Use | |
318 | <citerefentry><refentrytitle>sd_bus_error_set</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
319 | or one of its variants to set <parameter>ret_error</parameter> and return a negative integer | |
320 | from a callback with a single function call. To send an error reply after a callback has already | |
321 | finished, use | |
322 | <citerefentry><refentrytitle>sd_bus_reply_method_errno</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
323 | or one of its variants.</para> | |
324 | ||
325 | <para>For all functions, a match slot is created internally. If the output parameter | |
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326 | <replaceable>slot</replaceable> is <constant>NULL</constant>, a "floating" slot object is |
327 | created, see | |
afb9c0c9 | 328 | <citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>. |
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329 | Otherwise, a pointer to the slot object is returned. In that case, the reference to the slot |
330 | object should be dropped when the vtable is not needed anymore, see | |
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331 | <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>. |
332 | </para> | |
333 | ||
334 | <refsect2> | |
335 | <title>The <structname>sd_bus_vtable</structname> array</title> | |
336 | ||
337 | <para>The array consists of the structures of type <structname>sd_bus_vtable</structname>, but it | |
338 | should never be filled in manually, but through one of the following macros:</para> | |
339 | ||
340 | <variablelist> | |
341 | <varlistentry> | |
342 | <term><constant>SD_BUS_VTABLE_START()</constant></term> | |
343 | <term><constant>SD_BUS_VTABLE_END</constant></term> | |
344 | ||
345 | <listitem><para>Those must always be the first and last element.</para></listitem> | |
346 | </varlistentry> | |
347 | ||
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348 | <varlistentry> |
349 | <term><constant>SD_BUS_METHOD_WITH_ARGS_OFFSET()</constant></term> | |
350 | <term><constant>SD_BUS_METHOD_WITH_ARGS()</constant></term> | |
351 | ||
352 | <listitem><para>Declare a D-Bus method with the name <replaceable>member</replaceable>, | |
353 | arguments <replaceable>args</replaceable> and result <replaceable>result</replaceable>. | |
354 | <replaceable>args</replaceable> expects a sequence of argument type/name pairs wrapped in the | |
355 | <constant>SD_BUS_ARGS()</constant> macro. The elements at even indices in this list describe the | |
356 | types of the method's arguments. The method's parameter signature is the concatenation of all the | |
357 | string literals at even indices in <replaceable>args</replaceable>. If a method has no parameters, | |
358 | pass <constant>SD_BUS_NO_ARGS</constant> to <replaceable>args</replaceable>. The elements at uneven | |
359 | indices describe the names of the method's arguments. <replaceable>result</replaceable> expects a | |
360 | sequence of type/name pairs wrapped in the <constant>SD_BUS_RESULT()</constant> macro in the same | |
361 | format as <constant>SD_BUS_ARGS()</constant>. The method's result signature is the concatenation of | |
362 | all the string literals at even indices in <replaceable>result</replaceable>. If a method has no | |
363 | result, pass <constant>SD_BUS_NO_RESULT</constant> to <replaceable>result</replaceable>. Note that | |
364 | argument types are expected to be quoted string literals and argument names are expected to be | |
365 | unquoted string literals. See below for a complete example.</para> | |
366 | ||
367 | <para>The handler function <replaceable>handler</replaceable> must be of type | |
368 | <function>sd_bus_message_handler_t</function>. It will be called to handle the incoming messages | |
369 | that call this method. It receives a pointer that is the <replaceable>userdata</replaceable> | |
370 | parameter passed to the registration function offset by <replaceable>offset</replaceable> bytes. | |
371 | This may be used to pass pointers to different fields in the same data structure to different | |
372 | methods in the same vtable. To send a reply from <parameter>handler</parameter>, call | |
373 | <citerefentry><refentrytitle>sd_bus_reply_method_return</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
374 | with the message the callback was invoked with. Parameter <replaceable>flags</replaceable> is a | |
375 | combination of flags, see below.</para> | |
376 | ||
377 | <constant>SD_BUS_METHOD_WITH_ARGS()</constant> is a shorthand for calling | |
378 | <constant>SD_BUS_METHOD_WITH_ARGS_OFFSET()</constant> with an offset of zero. | |
379 | </listitem> | |
380 | </varlistentry> | |
381 | ||
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382 | <varlistentry> |
383 | <term><constant>SD_BUS_METHOD_WITH_NAMES_OFFSET()</constant></term> | |
384 | <term><constant>SD_BUS_METHOD_WITH_NAMES()</constant></term> | |
385 | <term><constant>SD_BUS_METHOD_WITH_OFFSET()</constant></term> | |
386 | <term><constant>SD_BUS_METHOD()</constant></term> | |
387 | ||
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388 | <listitem><para>Declare a D-Bus method with the name <replaceable>member</replaceable>, |
389 | parameter signature <replaceable>signature</replaceable>, result signature | |
390 | <replaceable>result</replaceable>. Parameters <replaceable>in_names</replaceable> and | |
391 | <replaceable>out_names</replaceable> specify the argument names of the input and output | |
eff7c2d3 | 392 | arguments in the function signature. <replaceable>in_names</replaceable> and |
9b62e232 | 393 | <replaceable>out_names</replaceable> should be created using the |
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394 | <constant>SD_BUS_PARAM()</constant> macro, see below. In all other regards, this macro behaves |
395 | exactly the same as <constant>SD_BUS_METHOD_WITH_ARGS_OFFSET()</constant>.</para> | |
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396 | |
397 | <para><constant>SD_BUS_METHOD_WITH_NAMES()</constant>, | |
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398 | <constant>SD_BUS_METHOD_WITH_OFFSET()</constant>, and <constant>SD_BUS_METHOD()</constant> |
399 | are variants which specify zero offset (<replaceable>userdata</replaceable> parameter is | |
400 | passed with no change), leave the names unset (i.e. no parameter names), or both.</para> | |
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401 | |
402 | <para>Prefer using <constant>SD_BUS_METHOD_WITH_ARGS_OFFSET()</constant> and | |
403 | <constant>SD_BUS_METHOD_WITH_ARGS()</constant> over these macros as they allow specifying argument | |
404 | types and names next to each other which is less error-prone than first specifying all argument | |
405 | types followed by specifying all argument names.</para> | |
afb9c0c9 ZJS |
406 | </listitem> |
407 | </varlistentry> | |
408 | ||
eff7c2d3 DDM |
409 | <varlistentry> |
410 | <term><constant>SD_BUS_SIGNAL_WITH_ARGS()</constant></term> | |
411 | ||
412 | <listitem><para>>Declare a D-Bus signal with the name <replaceable>member</replaceable> and | |
413 | arguments <replaceable>args</replaceable>. <replaceable>args</replaceable> expects a sequence of | |
414 | argument type/name pairs wrapped in the <constant>SD_BUS_ARGS()</constant> macro. The elements at | |
415 | even indices in this list describe the types of the signal's arguments. The signal's parameter | |
416 | signature is the concatenation of all the string literals at even indices in | |
417 | <replaceable>args</replaceable>. If a signal has no parameters, pass | |
418 | <constant>SD_BUS_NO_ARGS</constant> to <replaceable>args</replaceable>. The elements at uneven | |
419 | indices describe the names of the signal's arguments. Parameter <replaceable>flags</replaceable> is | |
420 | a combination of flags. See below for a complete example.</para></listitem> | |
421 | </varlistentry> | |
422 | ||
afb9c0c9 ZJS |
423 | <varlistentry> |
424 | <term><constant>SD_BUS_SIGNAL_WITH_NAMES()</constant></term> | |
425 | <term><constant>SD_BUS_SIGNAL()</constant></term> | |
426 | ||
427 | <listitem><para>Declare a D-Bus signal with the name <replaceable>member</replaceable>, | |
428 | parameter signature <replaceable>signature</replaceable>, and argument names | |
429 | <replaceable>names</replaceable>. <replaceable>names</replaceable> should be | |
430 | created using the <constant>SD_BUS_PARAM()</constant> macro, see below. | |
431 | Parameter <replaceable>flags</replaceable> is a combination of flags, see below. | |
432 | </para> | |
433 | ||
eff7c2d3 DDM |
434 | <para><constant>SD_BUS_SIGNAL()</constant> is equivalent to |
435 | <constant>SD_BUS_SIGNAL_WITH_NAMES()</constant> with the <replaceable>names</replaceable> parameter | |
436 | unset (i.e. no parameter names).</para> | |
437 | ||
438 | <para>Prefer using <constant>SD_BUS_SIGNAL_WITH_ARGS()</constant> over these macros as it allows | |
439 | specifying argument types and names next to each other which is less error-prone than first | |
440 | specifying all argument types followed by specifying all argument names.</para> | |
afb9c0c9 ZJS |
441 | </listitem> |
442 | </varlistentry> | |
443 | ||
444 | <varlistentry> | |
445 | <term><constant>SD_BUS_WRITABLE_PROPERTY()</constant></term> | |
446 | <term><constant>SD_BUS_PROPERTY()</constant></term> | |
447 | ||
50b88e87 DDM |
448 | <listitem><para>Declare a D-Bus property with the name <replaceable>member</replaceable> |
449 | and value signature <replaceable>signature</replaceable>. Parameters | |
450 | <replaceable>get</replaceable> and <replaceable>set</replaceable> are the getter and | |
451 | setter methods. They are called with a pointer that is the | |
452 | <replaceable>userdata</replaceable> parameter passed to the registration function offset | |
453 | by <replaceable>offset</replaceable> bytes. This may be used pass pointers to different | |
454 | fields in the same data structure to different setters and getters in the same vtable. | |
455 | Parameter <replaceable>flags</replaceable> is a combination of flags, see below.</para> | |
456 | ||
457 | <para>The setter and getter methods may be omitted (specified as | |
6ba8071c | 458 | <constant>NULL</constant>), if the property is one of the basic types or |
50b88e87 DDM |
459 | <literal>as</literal> in case of read-only properties. In those cases, the |
460 | <replaceable>userdata</replaceable> and <replaceable>offset</replaceable> parameters must | |
6ba8071c | 461 | together point to a valid variable of the corresponding type. A default setter and getter |
50b88e87 | 462 | will be provided, which simply copy the argument between this variable and the message. |
afb9c0c9 ZJS |
463 | </para> |
464 | ||
50b88e87 DDM |
465 | <para><constant>SD_BUS_PROPERTY()</constant> is used to define a read-only property. |
466 | </para></listitem> | |
afb9c0c9 ZJS |
467 | </varlistentry> |
468 | ||
469 | <varlistentry> | |
470 | <term><constant>SD_BUS_PARAM()</constant></term> | |
50b88e87 DDM |
471 | <listitem><para>Parameter names should be wrapped in this macro, see the example below. |
472 | </para></listitem> | |
afb9c0c9 ZJS |
473 | </varlistentry> |
474 | </variablelist> | |
475 | </refsect2> | |
476 | ||
477 | <refsect2> | |
478 | <title>Flags</title> | |
479 | ||
480 | <para>The <replaceable>flags</replaceable> parameter is used to specify a combination of | |
481 | <ulink url="https://dbus.freedesktop.org/doc/dbus-specification.html#introspection-format">D-Bus annotations</ulink>. | |
482 | </para> | |
483 | ||
484 | <variablelist> | |
485 | <varlistentry> | |
486 | <term><constant>SD_BUS_VTABLE_DEPRECATED</constant></term> | |
487 | ||
488 | <listitem><para>Mark this vtable entry as deprecated using the | |
50b88e87 | 489 | <constant>org.freedesktop.DBus.Deprecated</constant> annotation in introspection data. If |
afb9c0c9 ZJS |
490 | specified for <constant>SD_BUS_VTABLE_START()</constant>, the annotation is applied to the |
491 | enclosing interface.</para></listitem> | |
492 | </varlistentry> | |
493 | ||
494 | <varlistentry> | |
495 | <term><constant>SD_BUS_VTABLE_HIDDEN</constant></term> | |
496 | ||
50b88e87 DDM |
497 | <listitem><para>Make this vtable entry hidden. It will not be shown in introspection data. |
498 | If specified for <constant>SD_BUS_VTABLE_START()</constant>, all entries in the array are | |
499 | hidden.</para></listitem> | |
afb9c0c9 ZJS |
500 | </varlistentry> |
501 | ||
502 | <varlistentry> | |
503 | <term><constant>SD_BUS_VTABLE_UNPRIVILEGED</constant></term> | |
504 | ||
505 | <listitem><para>Mark this vtable entry as unprivileged. If not specified, the | |
506 | <constant>org.freedesktop.systemd1.Privileged</constant> annotation with value | |
50b88e87 | 507 | <literal>true</literal> will be shown in introspection data.</para></listitem> |
afb9c0c9 ZJS |
508 | </varlistentry> |
509 | ||
510 | <varlistentry> | |
511 | <term><constant>SD_BUS_VTABLE_METHOD_NO_REPLY</constant></term> | |
512 | ||
513 | <listitem><para>Mark his vtable entry as a method that will not return a reply using the | |
514 | <constant>org.freedesktop.DBus.Method.NoReply</constant> annotation in introspection data. | |
515 | </para></listitem> | |
516 | </varlistentry> | |
517 | ||
518 | <varlistentry> | |
94c4bbe5 PB |
519 | <term><constant>SD_BUS_VTABLE_PROPERTY_CONST</constant></term> |
520 | <term><constant>SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE</constant></term> | |
521 | <term><constant>SD_BUS_VTABLE_PROPERTY_EMITS_INVALIDATION</constant></term> | |
afb9c0c9 ZJS |
522 | |
523 | <listitem><para>Those three flags correspond to different values of the | |
50b88e87 DDM |
524 | <constant>org.freedesktop.DBus.Property.EmitsChangedSignal</constant> annotation, which |
525 | specifies whether the | |
526 | <constant>org.freedesktop.DBus.Properties.PropertiesChanged</constant> signal is emitted | |
527 | whenever the property changes. <constant>SD_BUS_VTABLE_PROPERTY_CONST</constant> | |
528 | corresponds to <constant>const</constant> and means that the property never changes during | |
529 | the lifetime of the object it belongs to, so no signal needs to be emitted. | |
530 | <constant>SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE</constant> corresponds to | |
531 | <constant>true</constant> and means that the signal is emitted. | |
532 | <constant>SD_BUS_VTABLE_PROPERTY_EMITS_INVALIDATION</constant> corresponds to | |
533 | <constant>invalidates</constant> and means that the signal is emitted, but the value is | |
534 | not included in the signal.</para></listitem> | |
afb9c0c9 ZJS |
535 | </varlistentry> |
536 | ||
537 | <varlistentry> | |
538 | <term><constant>SD_BUS_VTABLE_PROPERTY_EXPLICIT</constant></term> | |
539 | ||
50b88e87 DDM |
540 | <listitem><para>Mark this vtable property entry as requiring explicit request to for the |
541 | value to be shown (generally because the value is large or slow to calculate). This entry | |
542 | cannot be combined with <constant>SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE</constant>, and will | |
543 | not be shown in property listings by default (e.g. <command>busctl introspect</command>). | |
544 | This corresponds to the <constant>org.freedesktop.systemd1.Explicit</constant> annotation | |
545 | in introspection data.</para></listitem> | |
afb9c0c9 ZJS |
546 | </varlistentry> |
547 | </variablelist> | |
548 | </refsect2> | |
549 | </refsect1> | |
550 | ||
551 | <refsect1> | |
552 | <title>Examples</title> | |
553 | ||
554 | <example> | |
555 | <title>Create a simple listener on the bus</title> | |
556 | ||
557 | <programlisting><xi:include href="vtable-example.c" parse="text" /></programlisting> | |
558 | ||
50b88e87 DDM |
559 | <para>This creates a simple client on the bus (the user bus, when run as normal user). We may |
560 | use the D-Bus <constant>org.freedesktop.DBus.Introspectable.Introspect</constant> call to | |
561 | acquire the XML description of the interface:</para> | |
afb9c0c9 ZJS |
562 | |
563 | <programlisting><xi:include href="vtable-example.xml" parse="text" /></programlisting> | |
564 | </example> | |
565 | </refsect1> | |
566 | ||
567 | <refsect1> | |
568 | <title>Return Value</title> | |
569 | ||
85eeb142 DDM |
570 | <para>On success, <function>sd_bus_add_object_vtable()</function> and |
571 | <function>sd_bus_add_fallback_vtable()</function> return a non-negative integer. On | |
50b88e87 | 572 | failure, they return a negative errno-style error code.</para> |
afb9c0c9 ZJS |
573 | |
574 | <refsect2> | |
575 | <title>Errors</title> | |
576 | ||
577 | <para>Returned errors may indicate the following problems:</para> | |
578 | ||
579 | <variablelist> | |
580 | <varlistentry> | |
581 | <term><constant>-EINVAL</constant></term> | |
582 | ||
50b88e87 DDM |
583 | <listitem><para>One of the required parameters is <constant>NULL</constant> or invalid. A |
584 | reserved D-Bus interface was passed as the <replaceable>interface</replaceable> parameter. | |
585 | </para></listitem> | |
afb9c0c9 ZJS |
586 | </varlistentry> |
587 | ||
588 | <varlistentry> | |
589 | <term><constant>-ENOPKG</constant></term> | |
590 | ||
591 | <listitem><para>The bus cannot be resolved.</para></listitem> | |
592 | </varlistentry> | |
593 | ||
594 | <varlistentry> | |
595 | <term><constant>-ECHILD</constant></term> | |
596 | ||
597 | <listitem><para>The bus was created in a different process.</para></listitem> | |
598 | </varlistentry> | |
599 | ||
600 | <varlistentry> | |
601 | <term><constant>-ENOMEM</constant></term> | |
602 | ||
603 | <listitem><para>Memory allocation failed.</para></listitem> | |
604 | </varlistentry> | |
605 | ||
606 | <varlistentry> | |
607 | <term><constant>-EPROTOTYPE</constant></term> | |
608 | ||
609 | <listitem><para><function>sd_bus_add_object_vtable</function> and | |
50b88e87 DDM |
610 | <function>sd_bus_add_fallback_vtable</function> have been both called for the same bus |
611 | object path, which is not allowed.</para></listitem> | |
afb9c0c9 ZJS |
612 | </varlistentry> |
613 | ||
614 | <varlistentry> | |
615 | <term><constant>-EEXIST</constant></term> | |
616 | ||
617 | <listitem><para>This vtable has already been registered for this | |
618 | <replaceable>interface</replaceable> and <replaceable>path</replaceable>. | |
619 | </para></listitem> | |
620 | </varlistentry> | |
621 | </variablelist> | |
622 | </refsect2> | |
623 | </refsect1> | |
624 | ||
625 | <xi:include href="libsystemd-pkgconfig.xml" /> | |
626 | ||
627 | <refsect1> | |
628 | <title>See Also</title> | |
629 | ||
630 | <para> | |
631 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
ad300028 DDM |
632 | <citerefentry><refentrytitle>busctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
633 | <citerefentry><refentrytitle>sd_bus_emit_properties_changed</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
634 | <citerefentry><refentrytitle>sd_bus_emit_object_added</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
afb9c0c9 ZJS |
635 | </para> |
636 | </refsect1> | |
637 | </refentry> |