1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2
3.. _cec-func-poll:
4
5**********
6cec poll()
7**********
8
9Name
10====
11
12cec-poll - Wait for some event on a file descriptor
13
14
15Synopsis
16========
17
18.. code-block:: c
19
20    #include <sys/poll.h>
21
22
23.. c:function:: int poll( struct pollfd *ufds, unsigned int nfds, int timeout )
24   :name: cec-poll
25
26Arguments
27=========
28
29``ufds``
30   List of FD events to be watched
31
32``nfds``
33   Number of FD events at the \*ufds array
34
35``timeout``
36   Timeout to wait for events
37
38
39Description
40===========
41
42With the :c:func:`poll() <cec-poll>` function applications can wait for CEC
43events.
44
45On success :c:func:`poll() <cec-poll>` returns the number of file descriptors
46that have been selected (that is, file descriptors for which the
47``revents`` field of the respective struct :c:type:`pollfd`
48is non-zero). CEC devices set the ``POLLIN`` and ``POLLRDNORM`` flags in
49the ``revents`` field if there are messages in the receive queue. If the
50transmit queue has room for new messages, the ``POLLOUT`` and
51``POLLWRNORM`` flags are set. If there are events in the event queue,
52then the ``POLLPRI`` flag is set. When the function times out it returns
53a value of zero, on failure it returns -1 and the ``errno`` variable is
54set appropriately.
55
56For more details see the :c:func:`poll() <cec-poll>` manual page.
57
58
59Return Value
60============
61
62On success, :c:func:`poll() <cec-poll>` returns the number structures which have
63non-zero ``revents`` fields, or zero if the call timed out. On error -1
64is returned, and the ``errno`` variable is set appropriately:
65
66``EBADF``
67    One or more of the ``ufds`` members specify an invalid file
68    descriptor.
69
70``EFAULT``
71    ``ufds`` references an inaccessible memory area.
72
73``EINTR``
74    The call was interrupted by a signal.
75
76``EINVAL``
77    The ``nfds`` value exceeds the ``RLIMIT_NOFILE`` value. Use
78    ``getrlimit()`` to obtain this value.
79