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>`.
33 CEC devices can send asynchronous events. These can be retrieved by
34 calling :c:func:`CEC_DQEVENT`. If the file descriptor is in
35 non-blocking mode and no event is pending, then it will return -1 and
36 set errno to the ``EAGAIN`` error code.
38 The internal event queues are per-filehandle and per-event type. If
39 there is no more room in a queue then the last event is overwritten with
40 the new one. This means that intermediate results can be thrown away but
41 that the latest event is always available. This also means that is it
42 possible to read two successive events that have the same value (e.g.
43 two :ref:`CEC_EVENT_STATE_CHANGE <CEC-EVENT-STATE-CHANGE>` events with
44 the same state). In that case the intermediate state changes were lost but
45 it is guaranteed that the state did change in between the two events.
47 .. tabularcolumns:: |p{1.2cm}|p{2.9cm}|p{13.4cm}|
49 .. c:type:: cec_event_state_change
51 .. flat-table:: struct cec_event_state_change
58 - The current physical address. This is ``CEC_PHYS_ADDR_INVALID`` if no
59 valid physical address is set.
62 - The current set of claimed logical addresses. This is 0 if no logical
63 addresses are claimed or if ``phys_addr`` is ``CEC_PHYS_ADDR_INVALID``.
64 If bit 15 is set (``1 << CEC_LOG_ADDR_UNREGISTERED``) then this device
65 has the unregistered logical address. In that case all other bits are 0.
68 .. c:type:: cec_event_lost_msgs
70 .. tabularcolumns:: |p{1.0cm}|p{2.0cm}|p{14.5cm}|
72 .. flat-table:: struct cec_event_lost_msgs
79 - Set to the number of lost messages since the filehandle was opened
80 or since the last time this event was dequeued for this
81 filehandle. The messages lost are the oldest messages. So when a
82 new message arrives and there is no more room, then the oldest
83 message is discarded to make room for the new one. The internal
84 size of the message queue guarantees that all messages received in
85 the last two seconds will be stored. Since messages should be
86 replied to within a second according to the CEC specification,
87 this is more than enough.
90 .. tabularcolumns:: |p{1.0cm}|p{4.2cm}|p{2.5cm}|p{8.8cm}|
94 .. flat-table:: struct cec_event
101 - :cspan:`1` Timestamp of the event in ns.
103 The timestamp has been taken from the ``CLOCK_MONOTONIC`` clock. To access
104 the same clock from userspace use :c:func:`clock_gettime`.
107 - :cspan:`1` The CEC event type, see :ref:`cec-events`.
110 - :cspan:`1` Event flags, see :ref:`cec-event-flags`.
116 - struct cec_event_state_change
118 - The new adapter state as sent by the :ref:`CEC_EVENT_STATE_CHANGE <CEC-EVENT-STATE-CHANGE>`
121 - struct cec_event_lost_msgs
123 - The number of lost messages as sent by the :ref:`CEC_EVENT_LOST_MSGS <CEC-EVENT-LOST-MSGS>`
127 .. tabularcolumns:: |p{5.6cm}|p{0.9cm}|p{11.0cm}|
131 .. flat-table:: CEC Events Types
136 * .. _`CEC-EVENT-STATE-CHANGE`:
138 - ``CEC_EVENT_STATE_CHANGE``
140 - Generated when the CEC Adapter's state changes. When open() is
141 called an initial event will be generated for that filehandle with
142 the CEC Adapter's state at that time.
143 * .. _`CEC-EVENT-LOST-MSGS`:
145 - ``CEC_EVENT_LOST_MSGS``
147 - Generated if one or more CEC messages were lost because the
148 application didn't dequeue CEC messages fast enough.
151 .. tabularcolumns:: |p{6.0cm}|p{0.6cm}|p{10.9cm}|
155 .. flat-table:: CEC Event Flags
160 * .. _`CEC-EVENT-FL-INITIAL-VALUE`:
162 - ``CEC_EVENT_FL_INITIAL_VALUE``
164 - Set for the initial events that are generated when the device is
165 opened. See the table above for which events do this. This allows
166 applications to learn the initial state of the CEC adapter at
174 On success 0 is returned, on error -1 and the ``errno`` variable is set
175 appropriately. The generic error codes are described at the
176 :ref:`Generic Error Codes <gen-errors>` chapter.