1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: CEC
3
4 .. _CEC_DQEVENT:
5
6 *****************
7 ioctl CEC_DQEVENT
8 *****************
9
10 Name
11 ====
12
13 CEC_DQEVENT - Dequeue a CEC event
14
15 Synopsis
16 ========
17
18 .. c:macro:: CEC_DQEVENT
19
20 ``int ioctl(int fd, CEC_DQEVENT, struct cec_event *argp)``
21
22 Arguments
23 =========
24
25 ``fd``
26 File descriptor returned by :c:func:`open()`.
27
28 ``argp``
29
30 Description
31 ===========
32
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.
37
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.
46
47 .. tabularcolumns:: |p{1.2cm}|p{2.9cm}|p{13.2cm}|
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 * - __u16
67 - ``have_conn_info``
68 - If non-zero, then HDMI connector information is available.
69 This field is only valid if ``CEC_CAP_CONNECTOR_INFO`` is set. If that
70 capability is set and ``have_conn_info`` is zero, then that indicates
71 that the HDMI connector device is not instantiated, either because
72 the HDMI driver is still configuring the device or because the HDMI
73 device was unbound.
74
75 .. c:type:: cec_event_lost_msgs
76
77 .. tabularcolumns:: |p{1.0cm}|p{2.0cm}|p{14.3cm}|
78
79 .. flat-table:: struct cec_event_lost_msgs
80 :header-rows: 0
81 :stub-columns: 0
82 :widths: 1 1 16
83
84 * - __u32
85 - ``lost_msgs``
86 - Set to the number of lost messages since the filehandle was opened
87 or since the last time this event was dequeued for this
88 filehandle. The messages lost are the oldest messages. So when a
89 new message arrives and there is no more room, then the oldest
90 message is discarded to make room for the new one. The internal
91 size of the message queue guarantees that all messages received in
92 the last two seconds will be stored. Since messages should be
93 replied to within a second according to the CEC specification,
94 this is more than enough.
95
96 .. tabularcolumns:: |p{1.0cm}|p{4.4cm}|p{2.5cm}|p{9.2cm}|
97
98 .. c:type:: cec_event
99
100 .. flat-table:: struct cec_event
101 :header-rows: 0
102 :stub-columns: 0
103 :widths: 1 1 8
104
105 * - __u64
106 - ``ts``
107 - Timestamp of the event in ns.
108
109 The timestamp has been taken from the ``CLOCK_MONOTONIC`` clock.
110
111 To access the same clock from userspace use :c:func:`clock_gettime`.
112 * - __u32
113 - ``event``
114 - The CEC event type, see :ref:`cec-events`.
115 * - __u32
116 - ``flags``
117 - Event flags, see :ref:`cec-event-flags`.
118 * - union {
119 - (anonymous)
120 * - struct cec_event_state_change
121 - ``state_change``
122 - The new adapter state as sent by the :ref:`CEC_EVENT_STATE_CHANGE <CEC-EVENT-STATE-CHANGE>`
123 event.
124 * - struct cec_event_lost_msgs
125 - ``lost_msgs``
126 - The number of lost messages as sent by the :ref:`CEC_EVENT_LOST_MSGS <CEC-EVENT-LOST-MSGS>`
127 event.
128 * - }
129 -
130
131 .. tabularcolumns:: |p{5.6cm}|p{0.9cm}|p{10.8cm}|
132
133 .. _cec-events:
134
135 .. flat-table:: CEC Events Types
136 :header-rows: 0
137 :stub-columns: 0
138 :widths: 3 1 16
139
140 * .. _`CEC-EVENT-STATE-CHANGE`:
141
142 - ``CEC_EVENT_STATE_CHANGE``
143 - 1
144 - Generated when the CEC Adapter's state changes. When open() is
145 called an initial event will be generated for that filehandle with
146 the CEC Adapter's state at that time.
147 * .. _`CEC-EVENT-LOST-MSGS`:
148
149 - ``CEC_EVENT_LOST_MSGS``
150 - 2
151 - Generated if one or more CEC messages were lost because the
152 application didn't dequeue CEC messages fast enough.
153 * .. _`CEC-EVENT-PIN-CEC-LOW`:
154
155 - ``CEC_EVENT_PIN_CEC_LOW``
156 - 3
157 - Generated if the CEC pin goes from a high voltage to a low voltage.
158 Only applies to adapters that have the ``CEC_CAP_MONITOR_PIN``
159 capability set.
160 * .. _`CEC-EVENT-PIN-CEC-HIGH`:
161
162 - ``CEC_EVENT_PIN_CEC_HIGH``
163 - 4
164 - Generated if the CEC pin goes from a low voltage to a high voltage.
165 Only applies to adapters that have the ``CEC_CAP_MONITOR_PIN``
166 capability set.
167 * .. _`CEC-EVENT-PIN-HPD-LOW`:
168
169 - ``CEC_EVENT_PIN_HPD_LOW``
170 - 5
171 - Generated if the HPD pin goes from a high voltage to a low voltage.
172 Only applies to adapters that have the ``CEC_CAP_MONITOR_PIN``
173 capability set. When open() is called, the HPD pin can be read and
174 if the HPD is low, then an initial event will be generated for that
175 filehandle.
176 * .. _`CEC-EVENT-PIN-HPD-HIGH`:
177
178 - ``CEC_EVENT_PIN_HPD_HIGH``
179 - 6
180 - Generated if the HPD pin goes from a low voltage to a high voltage.
181 Only applies to adapters that have the ``CEC_CAP_MONITOR_PIN``
182 capability set. When open() is called, the HPD pin can be read and
183 if the HPD is high, then an initial event will be generated for that
184 filehandle.
185 * .. _`CEC-EVENT-PIN-5V-LOW`:
186
187 - ``CEC_EVENT_PIN_5V_LOW``
188 - 6
189 - Generated if the 5V pin goes from a high voltage to a low voltage.
190 Only applies to adapters that have the ``CEC_CAP_MONITOR_PIN``
191 capability set. When open() is called, the 5V pin can be read and
192 if the 5V is low, then an initial event will be generated for that
193 filehandle.
194 * .. _`CEC-EVENT-PIN-5V-HIGH`:
195
196 - ``CEC_EVENT_PIN_5V_HIGH``
197 - 7
198 - Generated if the 5V pin goes from a low voltage to a high voltage.
199 Only applies to adapters that have the ``CEC_CAP_MONITOR_PIN``
200 capability set. When open() is called, the 5V pin can be read and
201 if the 5V is high, then an initial event will be generated for that
202 filehandle.
203
204 .. tabularcolumns:: |p{6.0cm}|p{0.6cm}|p{10.7cm}|
205
206 .. _cec-event-flags:
207
208 .. flat-table:: CEC Event Flags
209 :header-rows: 0
210 :stub-columns: 0
211 :widths: 3 1 8
212
213 * .. _`CEC-EVENT-FL-INITIAL-STATE`:
214
215 - ``CEC_EVENT_FL_INITIAL_STATE``
216 - 1
217 - Set for the initial events that are generated when the device is
218 opened. See the table above for which events do this. This allows
219 applications to learn the initial state of the CEC adapter at
220 open() time.
221 * .. _`CEC-EVENT-FL-DROPPED-EVENTS`:
222
223 - ``CEC_EVENT_FL_DROPPED_EVENTS``
224 - 2
225 - Set if one or more events of the given event type have been dropped.
226 This is an indication that the application cannot keep up.
227
228
229 Return Value
230 ============
231
232 On success 0 is returned, on error -1 and the ``errno`` variable is set
233 appropriately. The generic error codes are described at the
234 :ref:`Generic Error Codes <gen-errors>` chapter.
235
236 The :ref:`ioctl CEC_DQEVENT <CEC_DQEVENT>` can return the following
237 error codes:
238
239 EAGAIN
240 This is returned when the filehandle is in non-blocking mode and there
241 are no pending events.
242
243 ERESTARTSYS
244 An interrupt (e.g. Ctrl-C) arrived while in blocking mode waiting for
245 events to arrive.
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.