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.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
.. _cec-func-poll:
**********
cec poll()
**********
Name
====
cec-poll - Wait for some event on a file descriptor
Synopsis
========
.. code-block:: c
#include <sys/poll.h>
.. c:function:: int poll( struct pollfd *ufds, unsigned int nfds, int timeout )
:name: cec-poll
Arguments
=========
``ufds``
List of FD events to be watched
``nfds``
Number of FD events at the \*ufds array
``timeout``
Timeout to wait for events
Description
===========
With the :c:func:`poll() <cec-poll>` function applications can wait for CEC
events.
On success :c:func:`poll() <cec-poll>` returns the number of file descriptors
that have been selected (that is, file descriptors for which the
``revents`` field of the respective struct :c:type:`pollfd`
is non-zero). CEC devices set the ``POLLIN`` and ``POLLRDNORM`` flags in
the ``revents`` field if there are messages in the receive queue. If the
transmit queue has room for new messages, the ``POLLOUT`` and
``POLLWRNORM`` flags are set. If there are events in the event queue,
then the ``POLLPRI`` flag is set. When the function times out it returns
a value of zero, on failure it returns -1 and the ``errno`` variable is
set appropriately.
For more details see the :c:func:`poll() <cec-poll>` manual page.
Return Value
============
On success, :c:func:`poll() <cec-poll>` returns the number structures which have
non-zero ``revents`` fields, or zero if the call timed out. On error -1
is returned, and the ``errno`` variable is set appropriately:
``EBADF``
One or more of the ``ufds`` members specify an invalid file
descriptor.
``EFAULT``
``ufds`` references an inaccessible memory area.
``EINTR``
The call was interrupted by a signal.
``EINVAL``
The ``nfds`` value exceeds the ``RLIMIT_NOFILE`` value. Use
``getrlimit()`` to obtain this value.
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