.. -*- coding: utf-8; mode: rst -*- .. _cec-func-poll: ********** cec poll() ********** Name ==== cec-poll - Wait for some event on a file descriptor Synopsis ======== .. code-block:: c #include .. 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() ` function applications can wait for CEC events. On success :c:func:`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() ` manual page. Return Value ============ On success, :c:func:`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`` argument is greater than ``OPEN_MAX``.