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