cec-ioc-dqevent.rst

  1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
  2.. c:namespace:: CEC
  3
  4.. _CEC_DQEVENT:
  5
  6*****************
  7ioctl CEC_DQEVENT
  8*****************
  9
 10Name
 11====
 12
 13CEC_DQEVENT - Dequeue a CEC event
 14
 15Synopsis
 16========
 17
 18.. c:macro:: CEC_DQEVENT
 19
 20``int ioctl(int fd, CEC_DQEVENT, struct cec_event *argp)``
 21
 22Arguments
 23=========
 24
 25``fd``
 26    File descriptor returned by :c:func:`open()`.
 27
 28``argp``
 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{13.2cm}|
 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
229Return Value
230============
231
232On success 0 is returned, on error -1 and the ``errno`` variable is set
233appropriately. The generic error codes are described at the
234:ref:`Generic Error Codes <gen-errors>` chapter.
235
236The :ref:`ioctl CEC_DQEVENT <CEC_DQEVENT>` can return the following
237error codes:
238
239EAGAIN
240    This is returned when the filehandle is in non-blocking mode and there
241    are no pending events.
242
243ERESTARTSYS
244    An interrupt (e.g. Ctrl-C) arrived while in blocking mode waiting for
245    events to arrive.