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Linux kernel mirror (for testing)
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linux
1.. -*- coding: utf-8; mode: rst -*-
2
3.. _CEC_DQEVENT:
4
5*****************
6ioctl CEC_DQEVENT
7*****************
8
9Name
10====
11
12CEC_DQEVENT - Dequeue a CEC event
13
14
15Synopsis
16========
17
18.. c:function:: int ioctl( int fd, CEC_DQEVENT, struct cec_event *argp )
19 :name: CEC_DQEVENT
20
21Arguments
22=========
23
24``fd``
25 File descriptor returned by :ref:`open() <cec-func-open>`.
26
27``argp``
28
29
30Description
31===========
32
33CEC devices can send asynchronous events. These can be retrieved by
34calling :c:func:`CEC_DQEVENT`. If the file descriptor is in
35non-blocking mode and no event is pending, then it will return -1 and
36set errno to the ``EAGAIN`` error code.
37
38The internal event queues are per-filehandle and per-event type. If
39there is no more room in a queue then the last event is overwritten with
40the new one. This means that intermediate results can be thrown away but
41that the latest event is always available. This also means that is it
42possible to read two successive events that have the same value (e.g.
43two :ref:`CEC_EVENT_STATE_CHANGE <CEC-EVENT-STATE-CHANGE>` events with
44the same state). In that case the intermediate state changes were lost but
45it is guaranteed that the state did change in between the two events.
46
47.. tabularcolumns:: |p{1.2cm}|p{2.9cm}|p{13.4cm}|
48
49.. c:type:: cec_event_state_change
50
51.. flat-table:: struct cec_event_state_change
52 :header-rows: 0
53 :stub-columns: 0
54 :widths: 1 1 8
55
56 * - __u16
57 - ``phys_addr``
58 - The current physical address. This is ``CEC_PHYS_ADDR_INVALID`` if no
59 valid physical address is set.
60 * - __u16
61 - ``log_addr_mask``
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.
66
67
68.. c:type:: cec_event_lost_msgs
69
70.. tabularcolumns:: |p{1.0cm}|p{2.0cm}|p{14.5cm}|
71
72.. flat-table:: struct cec_event_lost_msgs
73 :header-rows: 0
74 :stub-columns: 0
75 :widths: 1 1 16
76
77 * - __u32
78 - ``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.
88
89
90.. tabularcolumns:: |p{1.0cm}|p{4.2cm}|p{2.5cm}|p{8.8cm}|
91
92.. c:type:: cec_event
93
94.. flat-table:: struct cec_event
95 :header-rows: 0
96 :stub-columns: 0
97 :widths: 1 1 1 8
98
99 * - __u64
100 - ``ts``
101 - :cspan:`1` Timestamp of the event in ns.
102
103 The timestamp has been taken from the ``CLOCK_MONOTONIC`` clock. To access
104 the same clock from userspace use :c:func:`clock_gettime`.
105 * - __u32
106 - ``event``
107 - :cspan:`1` The CEC event type, see :ref:`cec-events`.
108 * - __u32
109 - ``flags``
110 - :cspan:`1` Event flags, see :ref:`cec-event-flags`.
111 * - union
112 - (anonymous)
113 -
114 -
115 * -
116 - struct cec_event_state_change
117 - ``state_change``
118 - The new adapter state as sent by the :ref:`CEC_EVENT_STATE_CHANGE <CEC-EVENT-STATE-CHANGE>`
119 event.
120 * -
121 - struct cec_event_lost_msgs
122 - ``lost_msgs``
123 - The number of lost messages as sent by the :ref:`CEC_EVENT_LOST_MSGS <CEC-EVENT-LOST-MSGS>`
124 event.
125
126
127.. tabularcolumns:: |p{5.6cm}|p{0.9cm}|p{11.0cm}|
128
129.. _cec-events:
130
131.. flat-table:: CEC Events Types
132 :header-rows: 0
133 :stub-columns: 0
134 :widths: 3 1 16
135
136 * .. _`CEC-EVENT-STATE-CHANGE`:
137
138 - ``CEC_EVENT_STATE_CHANGE``
139 - 1
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`:
144
145 - ``CEC_EVENT_LOST_MSGS``
146 - 2
147 - Generated if one or more CEC messages were lost because the
148 application didn't dequeue CEC messages fast enough.
149
150
151.. tabularcolumns:: |p{6.0cm}|p{0.6cm}|p{10.9cm}|
152
153.. _cec-event-flags:
154
155.. flat-table:: CEC Event Flags
156 :header-rows: 0
157 :stub-columns: 0
158 :widths: 3 1 8
159
160 * .. _`CEC-EVENT-FL-INITIAL-VALUE`:
161
162 - ``CEC_EVENT_FL_INITIAL_VALUE``
163 - 1
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
167 open() time.
168
169
170
171Return Value
172============
173
174On success 0 is returned, on error -1 and the ``errno`` variable is set
175appropriately. The generic error codes are described at the
176:ref:`Generic Error Codes <gen-errors>` chapter.