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diff --git a/src/libsystemd/sd_event_add_io.xml b/src/libsystemd/sd_event_add_io.xml new file mode 100644 index 0000000000..c3749164cd --- /dev/null +++ b/src/libsystemd/sd_event_add_io.xml @@ -0,0 +1,300 @@ +<?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 <systemd/sd-event.h></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 events + to watch 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 event source is triggered. The + <parameter>userdata</parameter> pointer will be passed to the + handler function, and 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. It's generally a subset of + the events watched, however may additionally include + <constant>EPOLLERR</constant> and <constant>EPOLLHUP</constant>. + </para> + + <para>By default, an event source will stay enabled + continuously (<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 event source set to <constant>SD_EVENT_ON</constant> will + fire continuously unless data is read from or written to the file + descriptor 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 if it is still referenced, + disable the event source using + <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry> + with <constant>SD_EVENT_OFF</constant>.</para> + + <para>If the second parameter of + <function>sd_event_add_io()</function> is + <constant>NULL</constant> 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 + starvation 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 mask of watched I/O events of an 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 + mask in.</para> + + <para><function>sd_event_source_set_io_events()</function> + configures the mask of watched I/O events of an event source created + previously with <function>sd_event_add_io()</function>. It takes the + event source object and the new event mask.</para> + + <para><function>sd_event_source_get_io_revents()</function> + retrieves the I/O event mask of currently seen but undispatched + events from an 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 event source created previously + with <function>sd_event_add_io()</function>. It takes the event + source object and returns the non-negative file descriptor + 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.</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 values 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> |