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