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+.. -*- coding: utf-8; mode: rst -*-
+
+.. _CEC_DQEVENT:
+
+*****************
+ioctl CEC_DQEVENT
+*****************
+
+Name
+====
+
+CEC_DQEVENT - Dequeue a CEC event
+
+
+Synopsis
+========
+
+.. cpp:function:: int ioctl( int fd, int request, struct cec_event *argp )
+
+Arguments
+=========
+
+``fd``
+ File descriptor returned by :ref:`open() <cec-func-open>`.
+
+``request``
+ CEC_DQEVENT
+
+``argp``
+
+
+Description
+===========
+
+.. note:: This documents the proposed CEC API. This API is not yet finalized
+ and is currently only available as a staging kernel module.
+
+CEC devices can send asynchronous events. These can be retrieved by
+calling :ref:`ioctl CEC_DQEVENT <CEC_DQEVENT>`. If the file descriptor is in
+non-blocking mode and no event is pending, then it will return -1 and
+set errno to the ``EAGAIN`` error code.
+
+The internal event queues are per-filehandle and per-event type. If
+there is no more room in a queue then the last event is overwritten with
+the new one. This means that intermediate results can be thrown away but
+that the latest event is always available. This also means that is it
+possible to read two successive events that have the same value (e.g.
+two :ref:`CEC_EVENT_STATE_CHANGE <CEC-EVENT-STATE-CHANGE>` events with
+the same state). In that case the intermediate state changes were lost but
+it is guaranteed that the state did change in between the two events.
+
+
+.. _cec-event-state-change_s:
+
+.. flat-table:: struct cec_event_state_change
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 1 8
+
+
+ - .. row 1
+
+ - __u16
+
+ - ``phys_addr``
+
+ - The current physical address.
+
+ - .. row 2
+
+ - __u16
+
+ - ``log_addr_mask``
+
+ - The current set of claimed logical addresses.
+
+
+
+.. _cec-event-lost-msgs_s:
+
+.. flat-table:: struct cec_event_lost_msgs
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 1 16
+
+
+ - .. row 1
+
+ - __u32
+
+ - ``lost_msgs``
+
+ - Set to the number of lost messages since the filehandle was opened
+ or since the last time this event was dequeued for this
+ filehandle. The messages lost are the oldest messages. So when a
+ new message arrives and there is no more room, then the oldest
+ message is discarded to make room for the new one. The internal
+ size of the message queue guarantees that all messages received in
+ the last two seconds will be stored. Since messages should be
+ replied to within a second according to the CEC specification,
+ this is more than enough.
+
+
+
+.. _cec-event:
+
+.. flat-table:: struct cec_event
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 1 1 8
+
+
+ - .. row 1
+
+ - __u64
+
+ - ``ts``
+
+ - Timestamp of the event in ns.
+ The timestamp has been taken from the ``CLOCK_MONOTONIC`` clock. To access
+ the same clock from userspace use :c:func:`clock_gettime(2)`.
+
+ -
+
+ - .. row 2
+
+ - __u32
+
+ - ``event``
+
+ - The CEC event type, see :ref:`cec-events`.
+
+ -
+
+ - .. row 3
+
+ - __u32
+
+ - ``flags``
+
+ - Event flags, see :ref:`cec-event-flags`.
+
+ -
+
+ - .. row 4
+
+ - union
+
+ - (anonymous)
+
+ -
+ -
+
+ - .. row 5
+
+ -
+ - struct cec_event_state_change
+
+ - ``state_change``
+
+ - The new adapter state as sent by the :ref:`CEC_EVENT_STATE_CHANGE <CEC-EVENT-STATE-CHANGE>`
+ event.
+
+ - .. row 6
+
+ -
+ - struct cec_event_lost_msgs
+
+ - ``lost_msgs``
+
+ - The number of lost messages as sent by the :ref:`CEC_EVENT_LOST_MSGS <CEC-EVENT-LOST-MSGS>`
+ event.
+
+
+
+.. _cec-events:
+
+.. flat-table:: CEC Events Types
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 3 1 16
+
+
+ - .. _`CEC-EVENT-STATE-CHANGE`:
+
+ - ``CEC_EVENT_STATE_CHANGE``
+
+ - 1
+
+ - Generated when the CEC Adapter's state changes. When open() is
+ called an initial event will be generated for that filehandle with
+ the CEC Adapter's state at that time.
+
+ - .. _`CEC-EVENT-LOST-MSGS`:
+
+ - ``CEC_EVENT_LOST_MSGS``
+
+ - 2
+
+ - Generated if one or more CEC messages were lost because the
+ application didn't dequeue CEC messages fast enough.
+
+
+
+.. _cec-event-flags:
+
+.. flat-table:: CEC Event Flags
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 3 1 8
+
+
+ - .. _`CEC-EVENT-FL-INITIAL-VALUE`:
+
+ - ``CEC_EVENT_FL_INITIAL_VALUE``
+
+ - 1
+
+ - Set for the initial events that are generated when the device is
+ opened. See the table above for which events do this. This allows
+ applications to learn the initial state of the CEC adapter at
+ open() time.
+
+
+
+Return Value
+============
+
+On success 0 is returned, on error -1 and the ``errno`` variable is set
+appropriately. The generic error codes are described at the
+:ref:`Generic Error Codes <gen-errors>` chapter.