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Diffstat (limited to 'Documentation/userspace-api/media/cec/cec-func-poll.rst')
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diff --git a/Documentation/userspace-api/media/cec/cec-func-poll.rst b/Documentation/userspace-api/media/cec/cec-func-poll.rst new file mode 100644 index 000000000000..ed3652d9bf17 --- /dev/null +++ b/Documentation/userspace-api/media/cec/cec-func-poll.rst @@ -0,0 +1,85 @@ +.. Permission is granted to copy, distribute and/or modify this +.. document under the terms of the GNU Free Documentation License, +.. Version 1.1 or any later version published by the Free Software +.. Foundation, with no Invariant Sections, no Front-Cover Texts +.. and no Back-Cover Texts. A copy of the license is included at +.. Documentation/userspace-api/media/fdl-appendix.rst. +.. +.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections + +.. _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. |