133 lines
4.2 KiB
ReStructuredText
133 lines
4.2 KiB
ReStructuredText
.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
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.. c:namespace:: V4L
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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:macro:: VIDIOC_SUBDEV_ENUM_FRAME_SIZE
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``int ioctl(int fd, VIDIOC_SUBDEV_ENUM_FRAME_SIZE, struct v4l2_subdev_frame_size_enum * argp)``
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Arguments
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=========
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``fd``
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File descriptor returned by :c: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 access the enumeration of frame sizes
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supported by a sub-device on the specified pad
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for the specified media bus format.
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Supported 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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The enumerations are defined by the driver, and indexed using the ``index`` field
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of the struct :c:type:`v4l2_subdev_frame_size_enum`.
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Each pair of ``pad`` and ``code`` correspond to a separate enumeration.
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Each enumeration starts with the ``index`` of 0, and
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the lowest invalid index marks the end of the enumeration.
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Therefore, to enumerate frame sizes allowed on the specified pad
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and using the specified mbus format, initialize the
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``pad``, ``which``, and ``code`` fields to desired values,
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and set ``index`` to 0.
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Then call the :ref:`VIDIOC_SUBDEV_ENUM_FRAME_SIZE` ioctl with a pointer to the
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structure.
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A successful call will return with minimum and maximum frame sizes filled in.
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Repeat with increasing ``index`` until ``EINVAL`` is received.
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``EINVAL`` means that either no more entries are available in the enumeration,
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or that an input parameter was 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{8.5cm}|
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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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- Index of the frame size in the enumeration belonging to the given pad
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and format. Filled in 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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Filled in by the application.
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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`. Filled in by the application.
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* - __u32
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- ``min_width``
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- Minimum frame width, in pixels. Filled in by the driver.
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* - __u32
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- ``max_width``
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- Maximum frame width, in pixels. Filled in by the driver.
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* - __u32
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- ``min_height``
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- Minimum frame height, in pixels. Filled in by the driver.
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* - __u32
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- ``max_height``
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- Maximum frame height, in pixels. Filled in by the driver.
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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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- ``stream``
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- Stream identifier.
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* - __u32
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- ``reserved``\ [7]
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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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