man: fully document sd-event interfaces

This completes the set of man pages for sd-event and contains some minor
other fixes for other man pages too.

The sd_event_set_name(3) man page is renamed to
sd_event_source_set_description(3), which is the correct name of the
concept today.

1 files changed, 300 insertions, 0 deletions

diff --git a/man/sd_event_add_io.xml b/man/sd_event_add_io.xml
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+<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!--
+  This file is part of systemd.
+
+  Copyright 2015 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<refentry id="sd_event_add_io" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+  <refentryinfo>
+    <title>sd_event_add_io</title>
+    <productname>systemd</productname>
+
+    <authorgroup>
+      <author>
+        <contrib>Developer</contrib>
+        <firstname>Lennart</firstname>
+        <surname>Poettering</surname>
+        <email>lennart@poettering.net</email>
+      </author>
+    </authorgroup>
+  </refentryinfo>
+
+  <refmeta>
+    <refentrytitle>sd_event_add_io</refentrytitle>
+    <manvolnum>3</manvolnum>
+  </refmeta>
+
+  <refnamediv>
+    <refname>sd_event_add_io</refname>
+    <refname>sd_event_source_get_io_events</refname>
+    <refname>sd_event_source_set_io_events</refname>
+    <refname>sd_event_source_get_io_revents</refname>
+    <refname>sd_event_source_get_io_fd</refname>
+    <refname>sd_event_source_set_io_fd</refname>
+    <refname>sd_event_source</refname>
+    <refname>sd_event_io_handler_t</refname>
+
+    <refpurpose>Add an I/O event source to an event loop</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <funcsynopsis>
+      <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
+
+      <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo>
+
+      <funcprototype>
+        <funcdef>typedef int (*<function>sd_event_io_handler_t</function>)</funcdef>
+        <paramdef>sd_event_source *<parameter>s</parameter></paramdef>
+        <paramdef>int <parameter>fd</parameter></paramdef>
+        <paramdef>uint32_t <parameter>revents</parameter></paramdef>
+        <paramdef>void *<parameter>userdata</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_add_io</function></funcdef>
+        <paramdef>sd_event *<parameter>event</parameter></paramdef>
+        <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
+        <paramdef>int <parameter>fd</parameter></paramdef>
+        <paramdef>uint32_t <parameter>events</parameter></paramdef>
+        <paramdef>sd_event_io_handler_t <parameter>handler</parameter></paramdef>
+        <paramdef>void *<parameter>userdata</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_source_get_io_events</function></funcdef>
+        <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+        <paramdef>uint32_t *<parameter>events</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_source_set_io_events</function></funcdef>
+        <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+        <paramdef>uint32_t <parameter>events</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_source_get_io_revents</function></funcdef>
+        <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+        <paramdef>uint32_t *<parameter>revents</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_source_get_io_fd</function></funcdef>
+        <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_event_source_set_io_fd</function></funcdef>
+        <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+        <paramdef>int <parameter>fd</parameter></paramdef>
+      </funcprototype>
+
+    </funcsynopsis>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para><function>sd_event_add_io()</function> adds a new I/O event
+    source to an event loop. The event loop object is specified in the
+    <parameter>event</parameter> parameter, the event source object is
+    returned in the <parameter>source</parameter> parameter. The
+    <parameter>fd</parameter> parameter takes the UNIX file descriptor
+    to watch, which may refer to a socket, a FIFO, a message queue, a
+    serial connection, a character device or any other file descriptor
+    compatible with Linux <citerefentry
+    project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry>. The
+    <parameter>events</parameter> parameter takes a bit mask of I/O
+    events to watch the file descriptor for, a combination of the
+    following event flags: <constant>EPOLLIN</constant>,
+    <constant>EPOLLOUT</constant>, <constant>EPOLLRDHUP</constant>,
+    <constant>EPOLLPRI</constant> and <constant>EPOLLET</constant>,
+    see <citerefentry
+    project='man-pages'><refentrytitle>epoll_ctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+    for details. The <parameter>handler</parameter> shall reference a
+    function to call when the I/O event source is triggered. The
+    handler function will be passed the
+    <parameter>userdata</parameter> pointer, which may be chosen
+    freely by the caller. The handler will also be passed the file
+    descriptor the event was seen on as well as the actual event flags
+    seen. It's generally a subset of the events watched, however may
+    additionally have <constant>EPOLLERR</constant> and
+    <constant>EPOLLHUP</constant> set.</para>
+
+    <para>By default, the I/O event source will stay enabled
+    continously (<constant>SD_EVENT_ON</constant>), but this may be
+    changed with
+    <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+    If the handler function returns a negative error code, it will be
+    disabled after the invocation, even if the
+    <constant>SD_EVENT_ON</constant> mode was requested before. Note
+    that an I/O event source set to <constant>SD_EVENT_ON</constant> will
+    fire continously unless data is read or written to the file
+    descriptor in order to reset the mask of events seen.
+    </para>
+
+    <para>Setting the I/O event mask to watch for to 0 does not mean
+    that the event source won't be triggered anymore, as
+    <constant>EPOLLHUP</constant> and <constant>EPOLLERR</constant>
+    may be triggered even with a zero event mask. To temporarily
+    disable an I/O event source use
+    <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    with <constant>SD_EVENT_OFF</constant> instead.</para>
+
+    <para>To destroy an event source object use
+    <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    but note that the event source is only removed from the event loop
+    when all references to the event source are dropped. To make sure
+    an event source does not fire anymore, even when there's still a
+    reference to it kept, consider setting the event source to
+    <constant>SD_EVENT_OFF</constant> with
+    <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+
+    <para>If the the second parameter of
+    <function>sd_event_add_io()</function> is passed as NULL no
+    reference to the event source object is returned. In this case the
+    event source is considered "floating", and will be destroyed
+    implicitly when the event loop itself is destroyed.</para>
+
+    <para>It is recommended to use
+    <function>sd_event_add_io()</function> only in conjunction with
+    file descriptors that have <constant>O_NONBLOCK</constant> set, to
+    ensure that all I/O operations from invoked handlers are properly
+    asynchronous and non-blocking. Using file descriptors without
+    <constant>O_NONBLOCK</constant> might result in unexpected
+    starving of other event sources. See <citerefentry
+    project='man-pages'><refentrytitle>fcntl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+    for details on enabling <constant>O_NONBLOCK</constant> mode.</para>
+
+    <para><function>sd_event_source_get_io_events()</function> retrieves
+    the configured I/O event mask to watch of an I/O event source created
+    previously with <function>sd_event_add_io()</function>. It takes
+    the event source object and a pointer to a variable to store the
+    event mask in.</para>
+
+    <para><function>sd_event_source_set_io_events()</function> changes the
+    configured I/O event mask to watch of an I/O event source created previously
+    with <function>sd_event_add_io()</function>. It takes the event
+    source object and the new event mask to set.</para>
+
+    <para><function>sd_event_source_get_io_events()</function>
+    retrieves the I/O event mask of currently seen but undispatched
+    events from an I/O event source created previously with
+    <function>sd_event_add_io()</function>. It takes the event source
+    object and a pointer to a variable to store the event mask
+    in. When called from a handler function on the handler's event
+    source object this will return the same mask as passed to the
+    handler's <parameter>revents</parameter> parameter. This call is
+    primarily useful to check for undispatched events of an event
+    source from the handler of an unrelated (possibly higher priority)
+    event source. Note the relation between
+    <function>sd_event_source_get_pending()</function> and
+    <function>sd_event_source_get_io_revents()</function>: both
+    functions will report non-zero results when there's an event
+    pending for the event source, but the former applies to all event
+    source types, the latter only to I/O event sources.</para>
+
+    <para><function>sd_event_source_get_io_fd()</function> retrieves
+    the UNIX file descriptor of an I/O event source created previously
+    with <function>sd_event_add_io()</function>. It takes the event
+    source object and returns the positive file descriptor in the return
+    value, or a negative error number on error (see below).</para>
+
+    <para><function>sd_event_source_set_io_fd()</function>
+    changes the UNIX file descriptor of an I/O event source created
+    previously with <function>sd_event_add_io()</function>. It takes
+    the event source object and the new file descriptor to set.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>Return Value</title>
+
+    <para>On success, these functions return 0 or a positive
+    integer. On failure, they return a negative errno-style error
+    code. </para>
+  </refsect1>
+
+  <refsect1>
+    <title>Errors</title>
+
+    <para>Returned errors may indicate the following problems:</para>
+
+    <variablelist>
+      <varlistentry>
+        <term><constant>-ENOMEM</constant></term>
+
+        <listitem><para>Not enough memory to allocate an object.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-EINVAL</constant></term>
+
+        <listitem><para>An invalid argument has been passed.</para></listitem>
+
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ESTALE</constant></term>
+
+        <listitem><para>The event loop is already terminated.</para></listitem>
+
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ECHILD</constant></term>
+
+        <listitem><para>The event loop has been created in a different process.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-EDOM</constant></term>
+
+        <listitem><para>The passed event source is not an I/O event source.</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-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_event_source_get_pending</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry project='man-pages'><refentrytitle>epoll_ctl</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+    </para>
+  </refsect1>
+
+</refentry>