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