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diff --git a/Documentation/media/uapi/v4l/vidioc-dqevent.rst b/Documentation/media/uapi/v4l/vidioc-dqevent.rst new file mode 100644 index 000000000000..73c0d5be62ee --- /dev/null +++ b/Documentation/media/uapi/v4l/vidioc-dqevent.rst @@ -0,0 +1,573 @@ +.. -*- coding: utf-8; mode: rst -*- + +.. _VIDIOC_DQEVENT: + +******************** +ioctl VIDIOC_DQEVENT +******************** + +Name +==== + +VIDIOC_DQEVENT - Dequeue event + + +Synopsis +======== + +.. cpp:function:: int ioctl( int fd, int request, struct v4l2_event *argp ) + + +Arguments +========= + +``fd`` + File descriptor returned by :ref:`open() <func-open>`. + +``request`` + VIDIOC_DQEVENT + +``argp`` + + +Description +=========== + +Dequeue an event from a video device. No input is required for this +ioctl. All the fields of the struct :ref:`v4l2_event <v4l2-event>` +structure are filled by the driver. The file handle will also receive +exceptions which the application may get by e.g. using the select system +call. + + +.. _v4l2-event: + +.. flat-table:: struct v4l2_event + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 1 + + + - .. row 1 + + - __u32 + + - ``type`` + + - + - Type of the event, see :ref:`event-type`. + + - .. row 2 + + - union + + - ``u`` + + - + - + + - .. row 3 + + - + - struct :ref:`v4l2_event_vsync <v4l2-event-vsync>` + + - ``vsync`` + + - Event data for event ``V4L2_EVENT_VSYNC``. + + - .. row 4 + + - + - struct :ref:`v4l2_event_ctrl <v4l2-event-ctrl>` + + - ``ctrl`` + + - Event data for event ``V4L2_EVENT_CTRL``. + + - .. row 5 + + - + - struct :ref:`v4l2_event_frame_sync <v4l2-event-frame-sync>` + + - ``frame_sync`` + + - Event data for event ``V4L2_EVENT_FRAME_SYNC``. + + - .. row 6 + + - + - struct :ref:`v4l2_event_motion_det <v4l2-event-motion-det>` + + - ``motion_det`` + + - Event data for event V4L2_EVENT_MOTION_DET. + + - .. row 7 + + - + - struct :ref:`v4l2_event_src_change <v4l2-event-src-change>` + + - ``src_change`` + + - Event data for event V4L2_EVENT_SOURCE_CHANGE. + + - .. row 8 + + - + - __u8 + + - ``data``\ [64] + + - Event data. Defined by the event type. The union should be used to + define easily accessible type for events. + + - .. row 9 + + - __u32 + + - ``pending`` + + - + - Number of pending events excluding this one. + + - .. row 10 + + - __u32 + + - ``sequence`` + + - + - Event sequence number. The sequence number is incremented for + every subscribed event that takes place. If sequence numbers are + not contiguous it means that events have been lost. + + - .. row 11 + + - struct timespec + + - ``timestamp`` + + - + - Event timestamp. The timestamp has been taken from the + ``CLOCK_MONOTONIC`` clock. To access the same clock outside V4L2, + use :c:func:`clock_gettime(2)`. + + - .. row 12 + + - u32 + + - ``id`` + + - + - The ID associated with the event source. If the event does not + have an associated ID (this depends on the event type), then this + is 0. + + - .. row 13 + + - __u32 + + - ``reserved``\ [8] + + - + - Reserved for future extensions. Drivers must set the array to + zero. + + + +.. _event-type: + +.. flat-table:: Event Types + :header-rows: 0 + :stub-columns: 0 + :widths: 3 1 4 + + + - .. row 1 + + - ``V4L2_EVENT_ALL`` + + - 0 + + - All events. V4L2_EVENT_ALL is valid only for + VIDIOC_UNSUBSCRIBE_EVENT for unsubscribing all events at once. + + - .. row 2 + + - ``V4L2_EVENT_VSYNC`` + + - 1 + + - This event is triggered on the vertical sync. This event has a + struct :ref:`v4l2_event_vsync <v4l2-event-vsync>` associated + with it. + + - .. row 3 + + - ``V4L2_EVENT_EOS`` + + - 2 + + - This event is triggered when the end of a stream is reached. This + is typically used with MPEG decoders to report to the application + when the last of the MPEG stream has been decoded. + + - .. row 4 + + - ``V4L2_EVENT_CTRL`` + + - 3 + + - This event requires that the ``id`` matches the control ID from + which you want to receive events. This event is triggered if the + control's value changes, if a button control is pressed or if the + control's flags change. This event has a struct + :ref:`v4l2_event_ctrl <v4l2-event-ctrl>` associated with it. + This struct contains much of the same information as struct + :ref:`v4l2_queryctrl <v4l2-queryctrl>` and struct + :ref:`v4l2_control <v4l2-control>`. + + If the event is generated due to a call to + :ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` or + :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`, then the + event will *not* be sent to the file handle that called the ioctl + function. This prevents nasty feedback loops. If you *do* want to + get the event, then set the ``V4L2_EVENT_SUB_FL_ALLOW_FEEDBACK`` + flag. + + This event type will ensure that no information is lost when more + events are raised than there is room internally. In that case the + struct :ref:`v4l2_event_ctrl <v4l2-event-ctrl>` of the + second-oldest event is kept, but the ``changes`` field of the + second-oldest event is ORed with the ``changes`` field of the + oldest event. + + - .. row 5 + + - ``V4L2_EVENT_FRAME_SYNC`` + + - 4 + + - Triggered immediately when the reception of a frame has begun. + This event has a struct + :ref:`v4l2_event_frame_sync <v4l2-event-frame-sync>` + associated with it. + + If the hardware needs to be stopped in the case of a buffer + underrun it might not be able to generate this event. In such + cases the ``frame_sequence`` field in struct + :ref:`v4l2_event_frame_sync <v4l2-event-frame-sync>` will not + be incremented. This causes two consecutive frame sequence numbers + to have n times frame interval in between them. + + - .. row 6 + + - ``V4L2_EVENT_SOURCE_CHANGE`` + + - 5 + + - This event is triggered when a source parameter change is detected + during runtime by the video device. It can be a runtime resolution + change triggered by a video decoder or the format change happening + on an input connector. This event requires that the ``id`` matches + the input index (when used with a video device node) or the pad + index (when used with a subdevice node) from which you want to + receive events. + + This event has a struct + :ref:`v4l2_event_src_change <v4l2-event-src-change>` + associated with it. The ``changes`` bitfield denotes what has + changed for the subscribed pad. If multiple events occurred before + application could dequeue them, then the changes will have the + ORed value of all the events generated. + + - .. row 7 + + - ``V4L2_EVENT_MOTION_DET`` + + - 6 + + - Triggered whenever the motion detection state for one or more of + the regions changes. This event has a struct + :ref:`v4l2_event_motion_det <v4l2-event-motion-det>` + associated with it. + + - .. row 8 + + - ``V4L2_EVENT_PRIVATE_START`` + + - 0x08000000 + + - Base event number for driver-private events. + + + +.. _v4l2-event-vsync: + +.. flat-table:: struct v4l2_event_vsync + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - __u8 + + - ``field`` + + - The upcoming field. See enum :ref:`v4l2_field <v4l2-field>`. + + + +.. _v4l2-event-ctrl: + +.. flat-table:: struct v4l2_event_ctrl + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 1 + + + - .. row 1 + + - __u32 + + - ``changes`` + + - + - A bitmask that tells what has changed. See + :ref:`ctrl-changes-flags`. + + - .. row 2 + + - __u32 + + - ``type`` + + - + - The type of the control. See enum + :ref:`v4l2_ctrl_type <v4l2-ctrl-type>`. + + - .. row 3 + + - union (anonymous) + + - + - + - + + - .. row 4 + + - + - __s32 + + - ``value`` + + - The 32-bit value of the control for 32-bit control types. This is + 0 for string controls since the value of a string cannot be passed + using :ref:`VIDIOC_DQEVENT`. + + - .. row 5 + + - + - __s64 + + - ``value64`` + + - The 64-bit value of the control for 64-bit control types. + + - .. row 6 + + - __u32 + + - ``flags`` + + - + - The control flags. See :ref:`control-flags`. + + - .. row 7 + + - __s32 + + - ``minimum`` + + - + - The minimum value of the control. See struct + :ref:`v4l2_queryctrl <v4l2-queryctrl>`. + + - .. row 8 + + - __s32 + + - ``maximum`` + + - + - The maximum value of the control. See struct + :ref:`v4l2_queryctrl <v4l2-queryctrl>`. + + - .. row 9 + + - __s32 + + - ``step`` + + - + - The step value of the control. See struct + :ref:`v4l2_queryctrl <v4l2-queryctrl>`. + + - .. row 10 + + - __s32 + + - ``default_value`` + + - + - The default value value of the control. See struct + :ref:`v4l2_queryctrl <v4l2-queryctrl>`. + + + +.. _v4l2-event-frame-sync: + +.. flat-table:: struct v4l2_event_frame_sync + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - __u32 + + - ``frame_sequence`` + + - The sequence number of the frame being received. + + + +.. _v4l2-event-src-change: + +.. flat-table:: struct v4l2_event_src_change + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - __u32 + + - ``changes`` + + - A bitmask that tells what has changed. See + :ref:`src-changes-flags`. + + + +.. _v4l2-event-motion-det: + +.. flat-table:: struct v4l2_event_motion_det + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - __u32 + + - ``flags`` + + - Currently only one flag is available: if + ``V4L2_EVENT_MD_FL_HAVE_FRAME_SEQ`` is set, then the + ``frame_sequence`` field is valid, otherwise that field should be + ignored. + + - .. row 2 + + - __u32 + + - ``frame_sequence`` + + - The sequence number of the frame being received. Only valid if the + ``V4L2_EVENT_MD_FL_HAVE_FRAME_SEQ`` flag was set. + + - .. row 3 + + - __u32 + + - ``region_mask`` + + - The bitmask of the regions that reported motion. There is at least + one region. If this field is 0, then no motion was detected at + all. If there is no ``V4L2_CID_DETECT_MD_REGION_GRID`` control + (see :ref:`detect-controls`) to assign a different region to + each cell in the motion detection grid, then that all cells are + automatically assigned to the default region 0. + + + +.. _ctrl-changes-flags: + +.. flat-table:: Control Changes + :header-rows: 0 + :stub-columns: 0 + :widths: 3 1 4 + + + - .. row 1 + + - ``V4L2_EVENT_CTRL_CH_VALUE`` + + - 0x0001 + + - This control event was triggered because the value of the control + changed. Special cases: Volatile controls do no generate this + event; If a control has the ``V4L2_CTRL_FLAG_EXECUTE_ON_WRITE`` + flag set, then this event is sent as well, regardless its value. + + - .. row 2 + + - ``V4L2_EVENT_CTRL_CH_FLAGS`` + + - 0x0002 + + - This control event was triggered because the control flags + changed. + + - .. row 3 + + - ``V4L2_EVENT_CTRL_CH_RANGE`` + + - 0x0004 + + - This control event was triggered because the minimum, maximum, + step or the default value of the control changed. + + + +.. _src-changes-flags: + +.. flat-table:: Source Changes + :header-rows: 0 + :stub-columns: 0 + :widths: 3 1 4 + + + - .. row 1 + + - ``V4L2_EVENT_SRC_CH_RESOLUTION`` + + - 0x0001 + + - This event gets triggered when a resolution change is detected at + an input. This can come from an input connector or from a video + decoder. + + +Return Value +============ + +On success 0 is returned, on error -1 and the ``errno`` variable is set +appropriately. The generic error codes are described at the +:ref:`Generic Error Codes <gen-errors>` chapter. |