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54f38fcae5
Since 2017, there is an space reserved for userspace API,
created by changeset 1d596dee38 ("docs: Create a user-space API guide").
As the media subsystem was one of the first subsystems to use
Sphinx, until this patch, we were keeping things on a separate
place.
Let's just use the new location, as having all uAPI altogether
will likely make things easier for developers.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
126 lines
3.8 KiB
ReStructuredText
126 lines
3.8 KiB
ReStructuredText
.. Permission is granted to copy, distribute and/or modify this
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.. document under the terms of the GNU Free Documentation License,
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.. Version 1.1 or any later version published by the Free Software
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.. Foundation, with no Invariant Sections, no Front-Cover Texts
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.. and no Back-Cover Texts. A copy of the license is included at
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.. Documentation/userspace-api/media/fdl-appendix.rst.
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..
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.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
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.. _VIDIOC_SUBDEV_ENUM_FRAME_SIZE:
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***********************************
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ioctl VIDIOC_SUBDEV_ENUM_FRAME_SIZE
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***********************************
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Name
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====
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VIDIOC_SUBDEV_ENUM_FRAME_SIZE - Enumerate media bus frame sizes
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Synopsis
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========
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.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_ENUM_FRAME_SIZE, struct v4l2_subdev_frame_size_enum * argp )
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:name: VIDIOC_SUBDEV_ENUM_FRAME_SIZE
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Arguments
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=========
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``fd``
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File descriptor returned by :ref:`open() <func-open>`.
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``argp``
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Pointer to struct :c:type:`v4l2_subdev_frame_size_enum`.
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Description
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===========
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This ioctl allows applications to enumerate all frame sizes supported by
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a sub-device on the given pad for the given media bus format. Supported
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formats can be retrieved with the
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:ref:`VIDIOC_SUBDEV_ENUM_MBUS_CODE`
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ioctl.
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To enumerate frame sizes applications initialize the ``pad``, ``which``
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, ``code`` and ``index`` fields of the struct
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:c:type:`v4l2_subdev_mbus_code_enum` and
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call the :ref:`VIDIOC_SUBDEV_ENUM_FRAME_SIZE` ioctl with a pointer to the
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structure. Drivers fill the minimum and maximum frame sizes or return an
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EINVAL error code if one of the input parameters is invalid.
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Sub-devices that only support discrete frame sizes (such as most
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sensors) will return one or more frame sizes with identical minimum and
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maximum values.
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Not all possible sizes in given [minimum, maximum] ranges need to be
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supported. For instance, a scaler that uses a fixed-point scaling ratio
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might not be able to produce every frame size between the minimum and
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maximum values. Applications must use the
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:ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>` ioctl to try the
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sub-device for an exact supported frame size.
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Available frame sizes may depend on the current 'try' formats at other
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pads of the sub-device, as well as on the current active links and the
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current values of V4L2 controls. See
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:ref:`VIDIOC_SUBDEV_G_FMT` for more
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information about try formats.
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.. c:type:: v4l2_subdev_frame_size_enum
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.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
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.. flat-table:: struct v4l2_subdev_frame_size_enum
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 1 2
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* - __u32
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- ``index``
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- Number of the format in the enumeration, set by the application.
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* - __u32
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- ``pad``
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- Pad number as reported by the media controller API.
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* - __u32
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- ``code``
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- The media bus format code, as defined in
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:ref:`v4l2-mbus-format`.
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* - __u32
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- ``min_width``
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- Minimum frame width, in pixels.
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* - __u32
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- ``max_width``
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- Maximum frame width, in pixels.
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* - __u32
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- ``min_height``
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- Minimum frame height, in pixels.
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* - __u32
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- ``max_height``
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- Maximum frame height, in pixels.
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* - __u32
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- ``which``
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- Frame sizes to be enumerated, from enum
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:ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
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* - __u32
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- ``reserved``\ [8]
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- Reserved for future extensions. Applications and drivers must set
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the array to zero.
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Return Value
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============
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On success 0 is returned, on error -1 and the ``errno`` variable is set
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appropriately. The generic error codes are described at the
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:ref:`Generic Error Codes <gen-errors>` chapter.
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EINVAL
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The struct
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:c:type:`v4l2_subdev_frame_size_enum`
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``pad`` references a non-existing pad, the ``code`` is invalid for
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the given pad or the ``index`` field is out of bounds.
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