1 .. -*- coding: utf-8; mode: rst -*-
12 CEC_DQEVENT - Dequeue a CEC event
18 .. c:function:: int ioctl( int fd, int request, struct cec_event *argp )
25 File descriptor returned by :ref:`open() <cec-func-open>`.
36 .. note:: This documents the proposed CEC API. This API is not yet finalized
37 and is currently only available as a staging kernel module.
39 CEC devices can send asynchronous events. These can be retrieved by
40 calling :c:func:`CEC_DQEVENT`. If the file descriptor is in
41 non-blocking mode and no event is pending, then it will return -1 and
42 set errno to the ``EAGAIN`` error code.
44 The internal event queues are per-filehandle and per-event type. If
45 there is no more room in a queue then the last event is overwritten with
46 the new one. This means that intermediate results can be thrown away but
47 that the latest event is always available. This also means that is it
48 possible to read two successive events that have the same value (e.g.
49 two :ref:`CEC_EVENT_STATE_CHANGE <CEC-EVENT-STATE-CHANGE>` events with
50 the same state). In that case the intermediate state changes were lost but
51 it is guaranteed that the state did change in between the two events.
54 .. _cec-event-state-change_s:
56 .. flat-table:: struct cec_event_state_change
68 - The current physical address.
76 - The current set of claimed logical addresses.
80 .. _cec-event-lost-msgs_s:
82 .. flat-table:: struct cec_event_lost_msgs
94 - Set to the number of lost messages since the filehandle was opened
95 or since the last time this event was dequeued for this
96 filehandle. The messages lost are the oldest messages. So when a
97 new message arrives and there is no more room, then the oldest
98 message is discarded to make room for the new one. The internal
99 size of the message queue guarantees that all messages received in
100 the last two seconds will be stored. Since messages should be
101 replied to within a second according to the CEC specification,
102 this is more than enough.
108 .. flat-table:: struct cec_event
120 - Timestamp of the event in ns.
121 The timestamp has been taken from the ``CLOCK_MONOTONIC`` clock. To access
122 the same clock from userspace use :c:func:`clock_gettime(2)`.
132 - The CEC event type, see :ref:`cec-events`.
142 - Event flags, see :ref:`cec-event-flags`.
158 - struct cec_event_state_change
162 - The new adapter state as sent by the :ref:`CEC_EVENT_STATE_CHANGE <CEC-EVENT-STATE-CHANGE>`
168 - struct cec_event_lost_msgs
172 - The number of lost messages as sent by the :ref:`CEC_EVENT_LOST_MSGS <CEC-EVENT-LOST-MSGS>`
179 .. flat-table:: CEC Events Types
185 - .. _`CEC-EVENT-STATE-CHANGE`:
187 - ``CEC_EVENT_STATE_CHANGE``
191 - Generated when the CEC Adapter's state changes. When open() is
192 called an initial event will be generated for that filehandle with
193 the CEC Adapter's state at that time.
195 - .. _`CEC-EVENT-LOST-MSGS`:
197 - ``CEC_EVENT_LOST_MSGS``
201 - Generated if one or more CEC messages were lost because the
202 application didn't dequeue CEC messages fast enough.
208 .. flat-table:: CEC Event Flags
214 - .. _`CEC-EVENT-FL-INITIAL-VALUE`:
216 - ``CEC_EVENT_FL_INITIAL_VALUE``
220 - Set for the initial events that are generated when the device is
221 opened. See the table above for which events do this. This allows
222 applications to learn the initial state of the CEC adapter at
230 On success 0 is returned, on error -1 and the ``errno`` variable is set
231 appropriately. The generic error codes are described at the
232 :ref:`Generic Error Codes <gen-errors>` chapter.