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<refentry id="cec-func-poll">
<refmeta>
<refentrytitle>cec poll()</refentrytitle>
&manvol;
</refmeta>
<refnamediv>
<refname>cec-poll</refname>
<refpurpose>Wait for some event on a file descriptor</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <sys/poll.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>poll</function></funcdef>
<paramdef>struct pollfd *<parameter>ufds</parameter></paramdef>
<paramdef>unsigned int <parameter>nfds</parameter></paramdef>
<paramdef>int <parameter>timeout</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
Note: this documents the proposed CEC API. This API is not yet finalized and
is currently only available as a staging kernel module.
</para>
<para>With the <function>poll()</function> function applications
can wait for CEC events.</para>
<para>On success <function>poll()</function> returns the number of
file descriptors that have been selected (that is, file descriptors
for which the <structfield>revents</structfield> field of the
respective <structname>pollfd</structname> structure is non-zero).
CEC devices set the <constant>POLLIN</constant> and
<constant>POLLRDNORM</constant> flags in the
<structfield>revents</structfield> field if there are messages in the
receive queue. If the transmit queue has room for new messages, the
<constant>POLLOUT</constant> and <constant>POLLWRNORM</constant>
flags are set. If there are events in the event queue, then the
<constant>POLLPRI</constant> flag is set.
When the function timed out it returns a value of zero, on
failure it returns <returnvalue>-1</returnvalue> and the
<varname>errno</varname> variable is set appropriately.
</para>
<para>For more details see the
<function>poll()</function> manual page.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, <function>poll()</function> returns the number
structures which have non-zero <structfield>revents</structfield>
fields, or zero if the call timed out. On error
<returnvalue>-1</returnvalue> is returned, and the
<varname>errno</varname> variable is set appropriately:</para>
<variablelist>
<varlistentry>
<term><errorcode>EBADF</errorcode></term>
<listitem>
<para>One or more of the <parameter>ufds</parameter> members
specify an invalid file descriptor.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><errorcode>EFAULT</errorcode></term>
<listitem>
<para><parameter>ufds</parameter> references an inaccessible
memory area.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><errorcode>EINTR</errorcode></term>
<listitem>
<para>The call was interrupted by a signal.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><errorcode>EINVAL</errorcode></term>
<listitem>
<para>The <parameter>nfds</parameter> argument is greater
than <constant>OPEN_MAX</constant>.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
</refentry>
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