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diff --git a/src/libsystemd/sd_event_add_time.xml b/src/libsystemd/sd_event_add_time.xml new file mode 100644 index 0000000000..5496b71529 --- /dev/null +++ b/src/libsystemd/sd_event_add_time.xml @@ -0,0 +1,313 @@ +<?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 2014 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_time" xmlns:xi="http://www.w3.org/2001/XInclude"> + + <refentryinfo> + <title>sd_event_add_time</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_time</refentrytitle> + <manvolnum>3</manvolnum> + </refmeta> + + <refnamediv> + <refname>sd_event_add_time</refname> + <refname>sd_event_source_get_time</refname> + <refname>sd_event_source_set_time</refname> + <refname>sd_event_source_get_time_accuracy</refname> + <refname>sd_event_source_set_time_accuracy</refname> + <refname>sd_event_source_get_time_clock</refname> + <refname>sd_event_time_handler_t</refname> + + <refpurpose>Add a timer 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_time_handler_t</function>)</funcdef> + <paramdef>sd_event_source *<parameter>s</parameter></paramdef> + <paramdef>uint64_t <parameter>usec</parameter></paramdef> + <paramdef>void *<parameter>userdata</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_event_add_time</function></funcdef> + <paramdef>sd_event *<parameter>event</parameter></paramdef> + <paramdef>sd_event_source **<parameter>source</parameter></paramdef> + <paramdef>clockid_t <parameter>clock</parameter></paramdef> + <paramdef>uint64_t <parameter>usec</parameter></paramdef> + <paramdef>uint64_t <parameter>accuracy</parameter></paramdef> + <paramdef>sd_event_time_handler_t <parameter>handler</parameter></paramdef> + <paramdef>void *<parameter>userdata</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_event_source_get_time</function></funcdef> + <paramdef>sd_event_source *<parameter>source</parameter></paramdef> + <paramdef>uint64_t *<parameter>usec</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_event_source_set_time</function></funcdef> + <paramdef>sd_event_source *<parameter>source</parameter></paramdef> + <paramdef>uint64_t <parameter>usec</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_event_source_get_time_accuracy</function></funcdef> + <paramdef>sd_event_source *<parameter>source</parameter></paramdef> + <paramdef>uint64_t *<parameter>usec</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_event_source_set_time_accuracy</function></funcdef> + <paramdef>sd_event_source *<parameter>source</parameter></paramdef> + <paramdef>uint64_t <parameter>usec</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_event_source_get_time_clock</function></funcdef> + <paramdef>sd_event_source *<parameter>source</parameter></paramdef> + <paramdef>clockid_t *<parameter>clock</parameter></paramdef> + </funcprototype> + + </funcsynopsis> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para><function>sd_event_add_time()</function> adds a new timer 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>clock</parameter> parameter takes a clock identifier, one + of <constant>CLOCK_REALTIME</constant>, <constant>CLOCK_MONOTONIC</constant>, <constant>CLOCK_BOOTTIME</constant>, + <constant>CLOCK_REALTIME_ALARM</constant>, or <constant>CLOCK_BOOTTIME_ALARM</constant>. See + <citerefentry><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry> for details + regarding the various types of clocks. The <parameter>usec</parameter> parameter specifies the earliest time, in + microseconds (µs), relative to the clock's epoch, when the timer shall be triggered. If a time already in the past + is specified (including <constant>0</constant>), this timer source "fires" immediately and is ready to be + dispatched. If the parameter is specified as <constant>UINT64_MAX</constant> the timer event will never elapse, + which may be used as an alternative to explicitly disabling a timer event source with + <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. The + <parameter>accuracy</parameter> parameter specifies an additional accuracy value in µs specifying how much the + timer event may be delayed. Use <constant>0</constant> to select the default accuracy (250ms). Use 1µs for maximum + accuracy. Consider specifying 60000000µs (1min) or larger for long-running events that may be delayed + substantially. Picking higher accuracy values allows the system to coalesce timer events more aggressively, + improving power efficiency. The <parameter>handler</parameter> parameter shall reference a function to call when + the timer elapses. The handler function will be passed the <parameter>userdata</parameter> pointer, which may be + chosen freely by the caller. The handler is also passed the configured trigger time, even if it is actually called + slightly later, subject to the specified accuracy value, the kernel timer slack (see + <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>), and additional + scheduling latencies. To query the actual time the handler was called use + <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> + + <para>By default, the timer will elapse once + (<constant>SD_EVENT_ONESHOT</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 a timer event set to <constant>SD_EVENT_ON</constant> will + fire continuously unless its configured time is updated using + <function>sd_event_source_set_time()</function>. + </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_time()</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>If the <parameter>handler</parameter> to + <function>sd_event_add_time()</function> is + <constant>NULL</constant>, and the event source fires, this will + be considered a request to exit the event loop. In this case, the + <parameter>userdata</parameter> parameter, cast to an integer, is + used for the exit code passed to + <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> + + <para>Use <constant>CLOCK_BOOTTIME_ALARM</constant> and + <constant>CLOCK_REALTIME_ALARM</constant> to define event sources + that may wake up the system from suspend.</para> + + <para>In order to set up relative timers (that is, relative to the + current time), retrieve the current time via + <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + add the desired timespan to it, and use the result as + the <parameter>usec</parameter> parameter to + <function>sd_event_add_time()</function>.</para> + + <para>In order to set up repetitive timers (that is, timers that + are triggered in regular intervals), set up the timer normally, + for the first invocation. Each time the event handler is invoked, + update the timer's trigger time with + <citerefentry><refentrytitle>sd_event_source_set_time</refentrytitle><manvolnum>3</manvolnum></citerefentry> for the next timer + iteration, and reenable the timer using + <function>sd_event_source_set_enabled()</function>. To calculate + the next point in time to pass to + <function>sd_event_source_set_time()</function>, either use as + base the <parameter>usec</parameter> parameter passed to the timer + callback, or the timestamp returned by + <function>sd_event_now()</function>. In the former case timer + events will be regular, while in the latter case the scheduling + latency will keep accumulating on the timer.</para> + + <para><function>sd_event_source_get_time()</function> retrieves + the configured time value of an event source created + previously with <function>sd_event_add_time()</function>. It takes + the event source object and a pointer to a variable to store the + time in, relative to the selected clock's epoch, in µs.</para> + + <para><function>sd_event_source_set_time()</function> changes the + time of an event source created previously with + <function>sd_event_add_time()</function>. It takes the event + source object and a time relative to the selected clock's epoch, + in µs.</para> + + <para><function>sd_event_source_get_time_accuracy()</function> + retrieves the configured accuracy value of an event source + created previously with <function>sd_event_add_time()</function>. It + takes the event source object and a pointer to a variable to store + the accuracy in. The accuracy is specified in µs.</para> + + <para><function>sd_event_source_set_time_accuracy()</function> + changes the configured accuracy of a timer event source created + previously with <function>sd_event_add_time()</function>. It takes + the event source object and accuracy, in µs.</para> + + <para><function>sd_event_source_get_time_clock()</function> + retrieves the configured clock of an event source created + previously with <function>sd_event_add_time()</function>. It takes + the event source object and a pointer to a variable to store the + clock identifier in.</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>-EOPNOTSUPP</constant></term> + + <listitem><para>The selected clock is not supported by the event loop implementation.</para></listitem> + + </varlistentry> + + <varlistentry> + <term><constant>-EDOM</constant></term> + + <listitem><para>The passed event source is not a timer 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_io</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 project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |