Orange Pi5 kernel

^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  1) .. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  2) .. c:namespace:: MC
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  3) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  4) .. _request-func-poll:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  5) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  6) **************
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  7) request poll()
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  8) **************
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  9) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) Name
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) ====
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) request-poll - Wait for some event on a file descriptor
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) Synopsis
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) ========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) .. code-block:: c
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20)     #include <sys/poll.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) .. c:function:: int poll( struct pollfd *ufds, unsigned int nfds, int timeout )
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) Arguments
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) =========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) ``ufds``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28)    List of file descriptor events to be watched
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) ``nfds``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31)    Number of file descriptor events at the \*ufds array
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) ``timeout``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34)    Timeout to wait for events
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) Description
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) ===========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) With the :c:func:`poll()` function applications can wait
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) for a request to complete.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) On success :c:func:`poll()` returns the number of file
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) descriptors that have been selected (that is, file descriptors for which the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) ``revents`` field of the respective struct :c:type:`pollfd`
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) is non-zero). Request file descriptor set the ``POLLPRI`` flag in ``revents``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46) when the request was completed.  When the function times out it returns
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) a value of zero, on failure it returns -1 and the ``errno`` variable is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) set appropriately.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) Attempting to poll for a request that is not yet queued will
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) set the ``POLLERR`` flag in ``revents``.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) Return Value
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) On success, :c:func:`poll()` returns the number of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) structures which have non-zero ``revents`` fields, or zero if the call
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58) timed out. On error -1 is returned, and the ``errno`` variable is set
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) appropriately:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) ``EBADF``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62)     One or more of the ``ufds`` members specify an invalid file
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63)     descriptor.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) ``EFAULT``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66)     ``ufds`` references an inaccessible memory area.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) ``EINTR``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69)     The call was interrupted by a signal.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) ``EINVAL``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72)     The ``nfds`` value exceeds the ``RLIMIT_NOFILE`` value. Use
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73)     ``getrlimit()`` to obtain this value.