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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/userspace-api/media/mediactl/request-func-poll.rst | |
parent | Initial commit. (diff) | |
download | linux-upstream/5.10.209.tar.xz linux-upstream/5.10.209.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | Documentation/userspace-api/media/mediactl/request-func-poll.rst | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/mediactl/request-func-poll.rst b/Documentation/userspace-api/media/mediactl/request-func-poll.rst new file mode 100644 index 000000000..ce0043dbe --- /dev/null +++ b/Documentation/userspace-api/media/mediactl/request-func-poll.rst @@ -0,0 +1,73 @@ +.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later +.. c:namespace:: MC + +.. _request-func-poll: + +************** +request poll() +************** + +Name +==== + +request-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 ) + +Arguments +========= + +``ufds`` + List of file descriptor events to be watched + +``nfds`` + Number of file descriptor events at the \*ufds array + +``timeout`` + Timeout to wait for events + +Description +=========== + +With the :c:func:`poll()` function applications can wait +for a request to complete. + +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). Request file descriptor set the ``POLLPRI`` flag in ``revents`` +when the request was completed. When the function times out it returns +a value of zero, on failure it returns -1 and the ``errno`` variable is +set appropriately. + +Attempting to poll for a request that is not yet queued will +set the ``POLLERR`` flag in ``revents``. + +Return Value +============ + +On success, :c:func:`poll()` returns the number of +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. |