Prompted by https://lists.freedesktop.org/archives/systemd-devel/2018-December/041817.html
This also drops all references to select() from our manpages. It's 2018
after all, people should use poll(), or ppoll() or epoll().
'3',
['SD_BUS_ERROR_END', 'SD_BUS_ERROR_MAP', 'sd_bus_error_map'],
''],
- ['sd_bus_get_fd', '3', [], ''],
+ ['sd_bus_get_fd', '3', ['sd_bus_get_events', 'sd_bus_get_timeout'], ''],
['sd_bus_get_n_queued_read', '3', ['sd_bus_get_n_queued_write'], ''],
['sd_bus_is_open', '3', ['sd_bus_is_ready'], ''],
['sd_bus_message_append', '3', ['sd_bus_message_appendv'], ''],
'sd_bus_track_unref',
'sd_bus_track_unrefp'],
''],
+ ['sd_bus_wait', '3', [], ''],
['sd_event_add_child',
'3',
['sd_event_child_handler_t', 'sd_event_source_get_child_pid'],
<para>The <function>sd_bus_get_event()</function> returns the event loop object the specified bus object is
currently attached to, or <constant>NULL</constant> if it is currently not attached to any.</para>
+
+ <para>Note that <function>sd_bus_attach_event()</function> is only one of three supported ways to implement I/O
+ event handling for bus connections. Alternatively use
+ <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry> for hooking up a
+ bus connection object with external or manual event loops. Or use
+ <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry> as a simple
+ synchronous, blocking I/O waiting call.</para>
</refsect1>
<refsect1>
<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_set_close_on_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
Copyright © 2016 Julian Orth
-->
-<refentry id="sd_bus_get_fd">
+<refentry id="sd_bus_get_fd" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_bus_get_fd</title>
<refnamediv>
<refname>sd_bus_get_fd</refname>
+ <refname>sd_bus_get_events</refname>
+ <refname>sd_bus_get_timeout</refname>
- <refpurpose>Get the file descriptor connected to the message bus</refpurpose>
+ <refpurpose>Get the file descriptor, I/O events and time-out to wait for from a message bus object</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcdef>int <function>sd_bus_get_fd</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
</funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_bus_get_events</function></funcdef>
+ <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_bus_get_timeout</function></funcdef>
+ <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
+ <paramdef>uint64_t *<parameter>timeout_usec</parameter></paramdef>
+ </funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
- <para>
- <function>sd_bus_get_fd()</function> returns the file descriptor used to
- communicate with the message bus. This descriptor can be used with
- <citerefentry
- project='die-net'><refentrytitle>select</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry
- project='die-net'><refentrytitle>poll</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- or similar functions to wait for incoming messages.
- </para>
-
- <para>
- If the bus was created with the
- <citerefentry><refentrytitle>sd_bus_set_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- function, then the <parameter>input_fd</parameter> used in that call is
- returned.
- </para>
+ <para><function>sd_bus_get_fd()</function> returns the file descriptor used to communicate from a message bus
+ object. This descriptor can be used with <citerefentry
+ project='man-pages'><refentrytitle>poll</refentrytitle><manvolnum>3</manvolnum></citerefentry> or a similar
+ function to wait for I/O events on the specified bus connection object. If the bus object was configured with the
+ <citerefentry><refentrytitle>sd_bus_set_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry> function, then
+ the <parameter>input_fd</parameter> file descriptor used in that call is returned.</para>
+
+ <para><function>sd_bus_get_events()</function> returns the I/O events to wait for, suitable for passing to
+ <function>poll()</function> or a similar call. Returns a combination of <constant>POLLIN</constant>,
+ <constant>POLLOUT</constant>, … events, or negative on error.</para>
+
+ <para><function>sd_bus_get_timeout()</function> returns the time-out in µs to pass to to
+ <function>poll()</function> or a similar call when waiting for events on the specified bus connection. The returned
+ time-out may be zero, in which case a subsequent I/O polling call should be invoked in non-blocking mode. The
+ returned timeout may be <constant>UINT64_MAX</constant> in which case the I/O polling call may block indefinitely,
+ without any applied time-out. Note that the returned time-out should be considered only a maximum sleeping time. It
+ is permissible (and even expected) that shorter time-outs are used by the calling program, in case other event
+ sources are polled in the same event loop. Note that the returned time-value is relative and specified in
+ microseconds. When converting this value in order to pass it as third argument to <function>poll()</function>
+ (which expects milliseconds), care should be taken to use a division that rounds up to ensure the I/O polling
+ operation doesn't sleep for shorter than necessary, which might result in unintended busy looping (alternatively,
+ use <citerefentry project='man-pages'><refentrytitle>ppoll</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ instead of plain <function>poll()</function>, which understands time-outs with nano-second granularity).</para>
+
+ <para>These three functions are useful to hook up a bus connection object with an external or manual event loop
+ involving <function>poll()</function> or a similar I/O polling call. Before each invocation of the I/O polling
+ call, all three functions should be invoked: the file descriptor returned by <function>sd_bus_get_fd()</function>
+ should be polled for the events indicated by <function>sd_bus_get_events()</function>, and the I/O call should
+ block for that up to the time-out returned by <function>sd_bus_get_timeout()</function>. After each I/O polling
+ call the bus connection needs to process incoming or outgoing data, by invoking
+ <citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+
+ <para>Note that these function are only one of three supported ways to implement I/O event handling for bus
+ connections. Alternatively use
+ <citerefentry><refentrytitle>sd_bus_attach_event</refentrytitle><manvolnum>3</manvolnum></citerefentry> to attach a
+ bus connection to an <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ event loop. Or use <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ as a simple synchronous, blocking I/O waiting call.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
- <para>
- Returns the file descriptor used for incoming messages from the message
- bus.
- </para>
+ <para><function>sd_bus_get_fd()</function> returns the file descriptor used for communication, or a negative
+ <varname>errno</varname>-style error code on error.</para>
+
+ <para><function>sd_bus_get_events()</function> returns the I/O event mask to use for I/O event watching, or a
+ negative <varname>errno</varname>-style error code on error.</para>
+
+ <para><function>sd_bus_get_timeout()</function> returns zero or positive on success, or a negative
+ <varname>errno</varname>-style error code on error.</para>
</refsect1>
+ <refsect1>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>-EINVAL</constant></term>
+
+ <listitem><para>An invalid bus object was passed.</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 connection has been terminated.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EPERM</constant></term>
+
+ <listitem><para>Two distinct file descriptors were passed for input and output using
+ <function>sd_bus_set_fd()</function>, which <function>sd_bus_get_fd()</function> cannot
+ return.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <xi:include href="libsystemd-pkgconfig.xml" />
+
<refsect1>
<title>See Also</title>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_set_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_bus_attach_event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>poll</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
Copyright © 2016 Julian Orth
-->
-<refentry id="sd_bus_process">
+<refentry id="sd_bus_process" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_bus_process</title>
<funcprototype>
<funcdef>int <function>sd_bus_process</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
- <paramdef>sd_bus_message **<parameter>r</parameter></paramdef>
+ <paramdef>sd_bus_message **<parameter>ret</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
- <para>
- <function>sd_bus_process()</function> drives the connection between the
- message bus and the client. That is, it handles connecting,
- authentication, and message processing. It should be called in a loop
- until no further progress can be made or an error occurs.
- </para>
-
- <para>
- Once no further progress can be made,
- <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- should be called. Alternatively the user can wait for incoming data on
- the file descriptor returned by
- <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+ <para><function>sd_bus_process()</function> drives the connection between the client and the message bus. That is,
+ it handles connecting, authentication, and message processing. When invoked pending I/O work is executed, and
+ queued incoming messages are dispatched to registered callbacks. Each time it is invoked a single operation is
+ executed. It returns zero when no operations were pending and positive if a message was processed. When zero is
+ returned the caller should synchronously poll for I/O events before calling into
+ <function>sd_bus_process()</function> again. For that either user the simple, synchronous
+ <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry> call, or hook up
+ the bus connection object to an external or manual event loop using
+ <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
</para>
- <para>
- <function>sd_bus_process</function> processes at most one incoming
- message per call. If the parameter <parameter>r</parameter> is not NULL
- and the call processed a message, <code>*r</code> is set to this message.
- The caller owns a reference to this message and should call
- <citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- when the message is no longer needed. If <parameter>r</parameter> is not
- NULL, progress was made, but no message was processed, <code>*r</code> is
- set to NULL.
- </para>
+ <para><function>sd_bus_process()</function> processes at most one incoming message per call. If the parameter
+ <parameter>ret</parameter> is not <constant>NULL</constant> and the call processed a message,
+ <parameter>*ret</parameter> is set to this message. The caller owns a reference to this message and should call
+ <citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> when the
+ message is no longer needed. If <parameter>ret</parameter> is not NULL, progress was made, but no message was
+ processed, <parameter>*ret</parameter> is set to <constant>NULL</constant>.</para>
+
+ <para>If a the bus object is connected to an
+ <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry> event loop (with
+ <citerefentry><refentrytitle>sd_bus_attach_event</refentrytitle><manvolnum>3</manvolnum></citerefentry>), it is not
+ necessary to call <function>sd_bus_process()</function> directly as it is invoked automatically when
+ necessary.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
- <para>
- If progress was made, a positive integer is returned. If no progress was
- made, 0 is returned. If an error occurs, a negative errno-style error code
- is returned.
- </para>
+ <para>If progress was made, a positive integer is returned. If no progress was made, 0 is returned. If an error
+ occurs, a negative <varname>errno</varname>-style error code is returned.</para>
</refsect1>
+ <refsect1>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>-EINVAL</constant></term>
+
+ <listitem><para>An invalid bus object was passed.</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 connection has been terminated already.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ECONNRESET</constant></term>
+
+ <listitem><para>The bus connection has been terminated just now.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EBUSY</constant></term>
+
+ <listitem><para>This function is already being called, i.e. <function>sd_bus_process()</function> has been
+ called from a callback function that itself was called by
+ <function>sd_bus_process()</function>.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </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_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_bus_attach_event</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
--- /dev/null
+<?xml version='1.0'?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!--
+ SPDX-License-Identifier: LGPL-2.1+
+
+ Copyright © 2016 Julian Orth
+-->
+
+<refentry id="sd_bus_wait" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+ <refentryinfo>
+ <title>sd_bus_wait</title>
+ <productname>systemd</productname>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>sd_bus_wait</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_bus_wait</refname>
+
+ <refpurpose>Wait for I/O on a bus connection</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_bus_wait</function></funcdef>
+ <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
+ <paramdef>uint64_t <parameter>timeout_usec</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_bus_wait()</function> synchronously waits for I/O on the specified bus connection object. This
+ function is supposed to be called whenever
+ <citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry> returns zero,
+ indicating that no work is pending on the connection. Internally, this call invokes <citerefentry
+ project='man-pages'><refentrytitle>ppoll</refentrytitle><manvolnum>3</manvolnum></citerefentry>, to wait for I/O on
+ the bus connection. If the <parameter>timeout_sec</parameter> parameter is specified, the call will block at most
+ for the specified amount of time in µs. Pass <constant>UINT64_MAX</constant> to permit it to sleep
+ indefinitely.</para>
+
+ <para>After each invocation of <function>sd_bus_wait()</function> the <function>sd_bus_process()</function> call
+ should be invoked in order to process any now pending I/O work.</para>
+
+ <para>Note that <function>sd_bus_wait()</function> is suitable only for simple programs as it does not permit
+ waiting for other I/O events. For more complex programs either connect the bus connection object to an external
+ event loop using <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ or to an <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry> event loop
+ using
+ <citerefentry><refentrytitle>sd_bus_attach_event</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>If any I/O was seen, a positive value is returned, zero otherwise. If an error occurs, a negative
+ <varname>errno</varname>-style error code is returned.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>-EINVAL</constant></term>
+
+ <listitem><para>An invalid bus object was passed.</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 connection has been terminated already.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </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_process</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_bus_attach_event</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>
projects / thirdparty / systemd.git / commitdiff
