1 .. -*- coding: utf-8; mode: rst -*-
12 CEC_DQEVENT - Dequeue a CEC event
18 .. c:function:: int ioctl( int fd, CEC_DQEVENT, struct cec_event *argp )
25 File descriptor returned by :ref:`open() <cec-func-open>`.
35 This documents the proposed CEC API. This API is not yet finalized
36 and is currently only available as a staging kernel module.
38 CEC devices can send asynchronous events. These can be retrieved by
39 calling :c:func:`CEC_DQEVENT`. If the file descriptor is in
40 non-blocking mode and no event is pending, then it will return -1 and
41 set errno to the ``EAGAIN`` error code.
43 The internal event queues are per-filehandle and per-event type. If
44 there is no more room in a queue then the last event is overwritten with
45 the new one. This means that intermediate results can be thrown away but
46 that the latest event is always available. This also means that is it
47 possible to read two successive events that have the same value (e.g.
48 two :ref:`CEC_EVENT_STATE_CHANGE <CEC-EVENT-STATE-CHANGE>` events with
49 the same state). In that case the intermediate state changes were lost but
50 it is guaranteed that the state did change in between the two events.
52 .. tabularcolumns:: |p{1.2cm}|p{2.9cm}|p{13.4cm}|
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.
79 .. tabularcolumns:: |p{1.0cm}|p{2.0cm}|p{14.5cm}|
81 .. _cec-event-lost-msgs_s:
83 .. flat-table:: struct cec_event_lost_msgs
95 - Set to the number of lost messages since the filehandle was opened
96 or since the last time this event was dequeued for this
97 filehandle. The messages lost are the oldest messages. So when a
98 new message arrives and there is no more room, then the oldest
99 message is discarded to make room for the new one. The internal
100 size of the message queue guarantees that all messages received in
101 the last two seconds will be stored. Since messages should be
102 replied to within a second according to the CEC specification,
103 this is more than enough.
106 .. tabularcolumns:: |p{1.0cm}|p{4.2cm}|p{2.5cm}|p{8.8cm}|
108 .. c:type:: cec_event
110 .. flat-table:: struct cec_event
122 - :cspan:`1` Timestamp of the event in ns.
124 The timestamp has been taken from the ``CLOCK_MONOTONIC`` clock. To access
125 the same clock from userspace use :c:func:`clock_gettime(2)`.
133 - :cspan:`1` The CEC event type, see :ref:`cec-events`.
141 - :cspan:`1` Event flags, see :ref:`cec-event-flags`.
155 - struct cec_event_state_change
159 - The new adapter state as sent by the :ref:`CEC_EVENT_STATE_CHANGE <CEC-EVENT-STATE-CHANGE>`
165 - struct cec_event_lost_msgs
169 - The number of lost messages as sent by the :ref:`CEC_EVENT_LOST_MSGS <CEC-EVENT-LOST-MSGS>`
173 .. tabularcolumns:: |p{5.6cm}|p{0.9cm}|p{11.0cm}|
177 .. flat-table:: CEC Events Types
183 - .. _`CEC-EVENT-STATE-CHANGE`:
185 - ``CEC_EVENT_STATE_CHANGE``
189 - Generated when the CEC Adapter's state changes. When open() is
190 called an initial event will be generated for that filehandle with
191 the CEC Adapter's state at that time.
193 - .. _`CEC-EVENT-LOST-MSGS`:
195 - ``CEC_EVENT_LOST_MSGS``
199 - Generated if one or more CEC messages were lost because the
200 application didn't dequeue CEC messages fast enough.
203 .. tabularcolumns:: |p{6.0cm}|p{0.6cm}|p{10.9cm}|
207 .. flat-table:: CEC Event Flags
213 - .. _`CEC-EVENT-FL-INITIAL-VALUE`:
215 - ``CEC_EVENT_FL_INITIAL_VALUE``
219 - Set for the initial events that are generated when the device is
220 opened. See the table above for which events do this. This allows
221 applications to learn the initial state of the CEC adapter at
229 On success 0 is returned, on error -1 and the ``errno`` variable is set
230 appropriately. The generic error codes are described at the
231 :ref:`Generic Error Codes <gen-errors>` chapter.