Documentation/media/uapi/cec/cec-ioc-dqevent.rst

   1 .. -*- coding: utf-8; mode: rst -*-
   2
   3 .. _CEC_DQEVENT:
   4
   5 *****************
   6 ioctl CEC_DQEVENT
   7 *****************
   8
   9 Name
  10 ====
  11
  12 CEC_DQEVENT - Dequeue a CEC event
  13
  14
  15 Synopsis
  16 ========
  17
  18 .. cpp:function:: int ioctl( int fd, int request, struct cec_event *argp )
  19
  20 Arguments
  21 =========
  22
  23 ``fd``
  24     File descriptor returned by :ref:`open() <cec-func-open>`.
  25
  26 ``request``
  27     CEC_DQEVENT
  28
  29 ``argp``
  30
  31
  32 Description
  33 ===========
  34
  35 .. note::
  36
  37    This documents the proposed CEC API. This API is not yet finalized
  38    and is currently only available as a staging kernel module.
  39
  40 CEC devices can send asynchronous events. These can be retrieved by
  41 calling :ref:`ioctl CEC_DQEVENT <CEC_DQEVENT>`. If the file descriptor is in
  42 non-blocking mode and no event is pending, then it will return -1 and
  43 set errno to the ``EAGAIN`` error code.
  44
  45 The internal event queues are per-filehandle and per-event type. If
  46 there is no more room in a queue then the last event is overwritten with
  47 the new one. This means that intermediate results can be thrown away but
  48 that the latest event is always available. This also means that is it
  49 possible to read two successive events that have the same value (e.g.
  50 two :ref:`CEC_EVENT_STATE_CHANGE <CEC-EVENT-STATE-CHANGE>` events with
  51 the same state). In that case the intermediate state changes were lost but
  52 it is guaranteed that the state did change in between the two events.
  53
  54
  55 .. _cec-event-state-change_s:
  56
  57 .. tabularcolumns:: |p{1.8cm}|p{1.8cm}|p{13.9cm}|
  58
  59 .. flat-table:: struct cec_event_state_change
  60     :header-rows:  0
  61     :stub-columns: 0
  62     :widths:       1 1 8
  63
  64
  65     -  .. row 1
  66
  67        -  __u16
  68
  69        -  ``phys_addr``
  70
  71        -  The current physical address.
  72
  73     -  .. row 2
  74
  75        -  __u16
  76
  77        -  ``log_addr_mask``
  78
  79        -  The current set of claimed logical addresses.
  80
  81
  82
  83 .. _cec-event-lost-msgs_s:
  84
  85 .. tabularcolumns:: |p{1.0cm}|p{1.0cm}|p{15.5cm}|
  86
  87 .. flat-table:: struct cec_event_lost_msgs
  88     :header-rows:  0
  89     :stub-columns: 0
  90     :widths:       1 1 16
  91
  92
  93     -  .. row 1
  94
  95        -  __u32
  96
  97        -  ``lost_msgs``
  98
  99        -  Set to the number of lost messages since the filehandle was opened
 100           or since the last time this event was dequeued for this
 101           filehandle. The messages lost are the oldest messages. So when a
 102           new message arrives and there is no more room, then the oldest
 103           message is discarded to make room for the new one. The internal
 104           size of the message queue guarantees that all messages received in
 105           the last two seconds will be stored. Since messages should be
 106           replied to within a second according to the CEC specification,
 107           this is more than enough.
 108
 109
 110
 111 .. _cec-event:
 112
 113 .. tabularcolumns:: |p{1.6cm}|p{1.6cm}|p{1.6cm}|p{12.7cm}|
 114
 115 .. flat-table:: struct cec_event
 116     :header-rows:  0
 117     :stub-columns: 0
 118     :widths:       1 1 1 8
 119
 120
 121     -  .. row 1
 122
 123        -  __u64
 124
 125        -  ``ts``
 126
 127        -  Timestamp of the event in ns.
 128           The timestamp has been taken from the ``CLOCK_MONOTONIC`` clock. To access
 129           the same clock from userspace use :c:func:`clock_gettime(2)`.
 130
 131        -
 132
 133     -  .. row 2
 134
 135        -  __u32
 136
 137        -  ``event``
 138
 139        -  The CEC event type, see :ref:`cec-events`.
 140
 141        -
 142
 143     -  .. row 3
 144
 145        -  __u32
 146
 147        -  ``flags``
 148
 149        -  Event flags, see :ref:`cec-event-flags`.
 150
 151        -
 152
 153     -  .. row 4
 154
 155        -  union
 156
 157        -  (anonymous)
 158
 159        -
 160        -
 161
 162     -  .. row 5
 163
 164        -
 165        -  struct cec_event_state_change
 166
 167        -  ``state_change``
 168
 169        -  The new adapter state as sent by the :ref:`CEC_EVENT_STATE_CHANGE <CEC-EVENT-STATE-CHANGE>`
 170           event.
 171
 172     -  .. row 6
 173
 174        -
 175        -  struct cec_event_lost_msgs
 176
 177        -  ``lost_msgs``
 178
 179        -  The number of lost messages as sent by the :ref:`CEC_EVENT_LOST_MSGS <CEC-EVENT-LOST-MSGS>`
 180           event.
 181
 182
 183
 184 .. _cec-events:
 185
 186 .. tabularcolumns:: |p{2.6cm}|p{0.9cm}|p{14.0cm}|
 187
 188 .. flat-table:: CEC Events Types
 189     :header-rows:  0
 190     :stub-columns: 0
 191     :widths:       3 1 16
 192
 193
 194     -  .. _`CEC-EVENT-STATE-CHANGE`:
 195
 196        -  ``CEC_EVENT_STATE_CHANGE``
 197
 198        -  1
 199
 200        -  Generated when the CEC Adapter's state changes. When open() is
 201           called an initial event will be generated for that filehandle with
 202           the CEC Adapter's state at that time.
 203
 204     -  .. _`CEC-EVENT-LOST-MSGS`:
 205
 206        -  ``CEC_EVENT_LOST_MSGS``
 207
 208        -  2
 209
 210        -  Generated if one or more CEC messages were lost because the
 211           application didn't dequeue CEC messages fast enough.
 212
 213
 214
 215 .. _cec-event-flags:
 216
 217 .. tabularcolumns:: |p{4.4cm}|p{1.5cm}|p{11.6cm}|
 218
 219 .. flat-table:: CEC Event Flags
 220     :header-rows:  0
 221     :stub-columns: 0
 222     :widths:       3 1 8
 223
 224
 225     -  .. _`CEC-EVENT-FL-INITIAL-VALUE`:
 226
 227        -  ``CEC_EVENT_FL_INITIAL_VALUE``
 228
 229        -  1
 230
 231        -  Set for the initial events that are generated when the device is
 232           opened. See the table above for which events do this. This allows
 233           applications to learn the initial state of the CEC adapter at
 234           open() time.
 235
 236
 237
 238 Return Value
 239 ============
 240
 241 On success 0 is returned, on error -1 and the ``errno`` variable is set
 242 appropriately. The generic error codes are described at the
 243 :ref:`Generic Error Codes <gen-errors>` chapter.