1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2 .. c:namespace:: CEC 3 4 .. _cec-func-poll: 5 6 ********** 7 cec poll() 8 ********** 9 10 Name 11 ==== 12 13 cec-poll - Wait for some event on a file descriptor 14 15 Synopsis 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 24 Arguments 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 36 Description 37 =========== 38 39 With the :c:func:`poll()` function applications can wait for CEC 40 events. 41 42 On success :c:func:`poll()` returns the number of file descriptors 43 that have been selected (that is, file descriptors for which the 44 ``revents`` field of the respective struct :c:type:`pollfd` 45 is non-zero). CEC devices set the ``POLLIN`` and ``POLLRDNORM`` flags in 46 the ``revents`` field if there are messages in the receive queue. If the 47 transmit queue has room for new messages, the ``POLLOUT`` and 48 ``POLLWRNORM`` flags are set. If there are events in the event queue, 49 then the ``POLLPRI`` flag is set. When the function times out it returns 50 a value of zero, on failure it returns -1 and the ``errno`` variable is 51 set appropriately. 52 53 For more details see the :c:func:`poll()` manual page. 54 55 Return Value 56 ============ 57 58 On success, :c:func:`poll()` returns the number structures which have 59 non-zero ``revents`` fields, or zero if the call timed out. On error -1 60 is 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.
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