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author | Ingo Molnar <mingo@kernel.org> | 2018-11-03 23:42:16 +0100 |
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committer | Ingo Molnar <mingo@kernel.org> | 2018-11-03 23:42:16 +0100 |
commit | 23a12ddee1ce28065b71f14ccc695b5a0c8a64ff (patch) | |
tree | cedaa1cde5b2557116e523c31552187804704093 /Documentation/media/uapi/mediactl/request-func-poll.rst | |
parent | 98f76206b33504b934209d16196477dfa519a807 (diff) | |
parent | bcb6fb5da77c2a228adf07cc9cb1a0c2aa2001c6 (diff) |
Merge branch 'core/urgent' into x86/urgent, to pick up objtool fix
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/media/uapi/mediactl/request-func-poll.rst')
-rw-r--r-- | Documentation/media/uapi/mediactl/request-func-poll.rst | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/Documentation/media/uapi/mediactl/request-func-poll.rst b/Documentation/media/uapi/mediactl/request-func-poll.rst new file mode 100644 index 000000000000..85191254f381 --- /dev/null +++ b/Documentation/media/uapi/mediactl/request-func-poll.rst @@ -0,0 +1,77 @@ +.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-or-later WITH no-invariant-sections + +.. _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 ) + :name: request-poll + +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() <request-func-poll>` function applications can wait +for a request to complete. + +On success :c:func:`poll() <request-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() <request-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. |