mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-21 19:53:59 +08:00
407e84cd1e
Sphinx 3.x broke support for the cdomain.py extension, as the c domain code was rewritten. Due to that, the c tags need to be re-written, in order to use the new c domain notation. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
374 lines
11 KiB
ReStructuredText
374 lines
11 KiB
ReStructuredText
.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
|
|
.. c:namespace:: V4L
|
|
|
|
.. _VIDIOC_DQEVENT:
|
|
|
|
********************
|
|
ioctl VIDIOC_DQEVENT
|
|
********************
|
|
|
|
Name
|
|
====
|
|
|
|
VIDIOC_DQEVENT - Dequeue event
|
|
|
|
Synopsis
|
|
========
|
|
|
|
.. c:macro:: VIDIOC_DQEVENT
|
|
|
|
``int ioctl(int fd, VIDIOC_DQEVENT, struct v4l2_event *argp)``
|
|
|
|
Arguments
|
|
=========
|
|
|
|
``fd``
|
|
File descriptor returned by :c:func:`open()`.
|
|
|
|
``argp``
|
|
Pointer to struct :c:type:`v4l2_event`.
|
|
|
|
Description
|
|
===========
|
|
|
|
Dequeue an event from a video device. No input is required for this
|
|
ioctl. All the fields of the struct :c:type:`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.
|
|
|
|
.. tabularcolumns:: |p{3.0cm}|p{4.4cm}|p{2.4cm}|p{7.7cm}|
|
|
|
|
.. c:type:: v4l2_event
|
|
|
|
.. cssclass: longtable
|
|
|
|
.. flat-table:: struct v4l2_event
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 1 1 2
|
|
|
|
* - __u32
|
|
- ``type``
|
|
- Type of the event, see :ref:`event-type`.
|
|
* - union {
|
|
- ``u``
|
|
* - struct :c:type:`v4l2_event_vsync`
|
|
- ``vsync``
|
|
- Event data for event ``V4L2_EVENT_VSYNC``.
|
|
* - struct :c:type:`v4l2_event_ctrl`
|
|
- ``ctrl``
|
|
- Event data for event ``V4L2_EVENT_CTRL``.
|
|
* - struct :c:type:`v4l2_event_frame_sync`
|
|
- ``frame_sync``
|
|
- Event data for event ``V4L2_EVENT_FRAME_SYNC``.
|
|
* - struct :c:type:`v4l2_event_motion_det`
|
|
- ``motion_det``
|
|
- Event data for event V4L2_EVENT_MOTION_DET.
|
|
* - struct :c:type:`v4l2_event_src_change`
|
|
- ``src_change``
|
|
- Event data for event V4L2_EVENT_SOURCE_CHANGE.
|
|
* - __u8
|
|
- ``data``\ [64]
|
|
- Event data. Defined by the event type. The union should be used to
|
|
define easily accessible type for events.
|
|
* - }
|
|
-
|
|
* - __u32
|
|
- ``pending``
|
|
- Number of pending events excluding this one.
|
|
* - __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.
|
|
* - 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`.
|
|
* - 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.
|
|
* - __u32
|
|
- ``reserved``\ [8]
|
|
- Reserved for future extensions. Drivers must set the array to
|
|
zero.
|
|
|
|
|
|
.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
|
|
|
|
.. cssclass:: longtable
|
|
|
|
.. _event-type:
|
|
|
|
.. flat-table:: Event Types
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 3 1 4
|
|
|
|
* - ``V4L2_EVENT_ALL``
|
|
- 0
|
|
- All events. V4L2_EVENT_ALL is valid only for
|
|
VIDIOC_UNSUBSCRIBE_EVENT for unsubscribing all events at once.
|
|
* - ``V4L2_EVENT_VSYNC``
|
|
- 1
|
|
- This event is triggered on the vertical sync. This event has a
|
|
struct :c:type:`v4l2_event_vsync` associated
|
|
with it.
|
|
* - ``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.
|
|
* - ``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
|
|
:c:type:`v4l2_event_ctrl` associated with it.
|
|
This struct contains much of the same information as struct
|
|
:ref:`v4l2_queryctrl <v4l2-queryctrl>` and struct
|
|
:c:type:`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 :c:type:`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.
|
|
* - ``V4L2_EVENT_FRAME_SYNC``
|
|
- 4
|
|
- Triggered immediately when the reception of a frame has begun.
|
|
This event has a struct
|
|
:c:type:`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
|
|
:c:type:`v4l2_event_frame_sync` will not
|
|
be incremented. This causes two consecutive frame sequence numbers
|
|
to have n times frame interval in between them.
|
|
* - ``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
|
|
:c:type:`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.
|
|
* - ``V4L2_EVENT_MOTION_DET``
|
|
- 6
|
|
- Triggered whenever the motion detection state for one or more of
|
|
the regions changes. This event has a struct
|
|
:c:type:`v4l2_event_motion_det`
|
|
associated with it.
|
|
* - ``V4L2_EVENT_PRIVATE_START``
|
|
- 0x08000000
|
|
- Base event number for driver-private events.
|
|
|
|
|
|
.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
|
|
|
|
.. c:type:: v4l2_event_vsync
|
|
|
|
.. flat-table:: struct v4l2_event_vsync
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 1 1 2
|
|
|
|
* - __u8
|
|
- ``field``
|
|
- The upcoming field. See enum :c:type:`v4l2_field`.
|
|
|
|
|
|
.. tabularcolumns:: |p{3.5cm}|p{3.0cm}|p{1.8cm}|p{8.5cm}|
|
|
|
|
.. c:type:: v4l2_event_ctrl
|
|
|
|
.. flat-table:: struct v4l2_event_ctrl
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 1 1 2
|
|
|
|
* - __u32
|
|
- ``changes``
|
|
- A bitmask that tells what has changed. See
|
|
:ref:`ctrl-changes-flags`.
|
|
* - __u32
|
|
- ``type``
|
|
- The type of the control. See enum
|
|
:c:type:`v4l2_ctrl_type`.
|
|
* - union {
|
|
- (anonymous)
|
|
* - __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`.
|
|
* - __s64
|
|
- ``value64``
|
|
- The 64-bit value of the control for 64-bit control types.
|
|
* - }
|
|
-
|
|
* - __u32
|
|
- ``flags``
|
|
- The control flags. See :ref:`control-flags`.
|
|
* - __s32
|
|
- ``minimum``
|
|
- The minimum value of the control. See struct
|
|
:ref:`v4l2_queryctrl <v4l2-queryctrl>`.
|
|
* - __s32
|
|
- ``maximum``
|
|
- The maximum value of the control. See struct
|
|
:ref:`v4l2_queryctrl <v4l2-queryctrl>`.
|
|
* - __s32
|
|
- ``step``
|
|
- The step value of the control. See struct
|
|
:ref:`v4l2_queryctrl <v4l2-queryctrl>`.
|
|
* - __s32
|
|
- ``default_value``
|
|
- The default value of the control. See struct
|
|
:ref:`v4l2_queryctrl <v4l2-queryctrl>`.
|
|
|
|
|
|
.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
|
|
|
|
.. c:type:: v4l2_event_frame_sync
|
|
|
|
.. flat-table:: struct v4l2_event_frame_sync
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 1 1 2
|
|
|
|
* - __u32
|
|
- ``frame_sequence``
|
|
- The sequence number of the frame being received.
|
|
|
|
|
|
.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
|
|
|
|
.. c:type:: v4l2_event_src_change
|
|
|
|
.. flat-table:: struct v4l2_event_src_change
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 1 1 2
|
|
|
|
* - __u32
|
|
- ``changes``
|
|
- A bitmask that tells what has changed. See
|
|
:ref:`src-changes-flags`.
|
|
|
|
|
|
.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
|
|
|
|
.. c:type:: v4l2_event_motion_det
|
|
|
|
.. flat-table:: struct v4l2_event_motion_det
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 1 1 2
|
|
|
|
* - __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.
|
|
* - __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.
|
|
* - __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.
|
|
|
|
|
|
.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
|
|
|
|
.. _ctrl-changes-flags:
|
|
|
|
.. flat-table:: Control Changes
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 3 1 4
|
|
|
|
* - ``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.
|
|
* - ``V4L2_EVENT_CTRL_CH_FLAGS``
|
|
- 0x0002
|
|
- This control event was triggered because the control flags
|
|
changed.
|
|
* - ``V4L2_EVENT_CTRL_CH_RANGE``
|
|
- 0x0004
|
|
- This control event was triggered because the minimum, maximum,
|
|
step or the default value of the control changed.
|
|
|
|
|
|
.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
|
|
|
|
.. _src-changes-flags:
|
|
|
|
.. flat-table:: Source Changes
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 3 1 4
|
|
|
|
* - ``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. Applications will have to query the new resolution (if
|
|
any, the signal may also have been lost).
|
|
|
|
For stateful decoders follow the guidelines in :ref:`decoder`.
|
|
Video Capture devices have to query the new timings using
|
|
:ref:`VIDIOC_QUERY_DV_TIMINGS` or
|
|
:ref:`VIDIOC_QUERYSTD <VIDIOC_QUERYSTD>`.
|
|
|
|
*Important*: even if the new video timings appear identical to the old
|
|
ones, receiving this event indicates that there was an issue with the
|
|
video signal and you must stop and restart streaming
|
|
(:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>`
|
|
followed by :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>`). The reason is
|
|
that many Video Capture devices are not able to recover from a temporary
|
|
loss of signal and so restarting streaming I/O is required in order for
|
|
the hardware to synchronize to the video signal.
|
|
|
|
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.
|