Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst

Source file repositories/reference/linux-study-clean/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst

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Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst
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Support Tooling And Documentation
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Support Tooling And Documentation: documentation
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Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
.. c:namespace:: V4L

.. _VIDIOC_SUBDEV_ENUM_FRAME_SIZE:

***********************************
ioctl VIDIOC_SUBDEV_ENUM_FRAME_SIZE
***********************************

Name
====

VIDIOC_SUBDEV_ENUM_FRAME_SIZE - Enumerate media bus frame sizes

Synopsis
========

.. c:macro:: VIDIOC_SUBDEV_ENUM_FRAME_SIZE

``int ioctl(int fd, VIDIOC_SUBDEV_ENUM_FRAME_SIZE, struct v4l2_subdev_frame_size_enum * argp)``

Arguments
=========

``fd``
    File descriptor returned by :c:func:`open()`.

``argp``
    Pointer to struct :c:type:`v4l2_subdev_frame_size_enum`.

Description
===========

This ioctl allows applications to access the enumeration of frame sizes
supported by a sub-device on the specified pad
for the specified media bus format.
Supported formats can be retrieved with the
:ref:`VIDIOC_SUBDEV_ENUM_MBUS_CODE`
ioctl.

The enumerations are defined by the driver, and indexed using the ``index`` field
of the struct :c:type:`v4l2_subdev_frame_size_enum`.
Each pair of ``pad`` and ``code`` correspond to a separate enumeration.
Each enumeration starts with the ``index`` of 0, and
the lowest invalid index marks the end of the enumeration.

Therefore, to enumerate frame sizes allowed on the specified pad
and using the specified mbus format, initialize the
``pad``, ``which``, and ``code`` fields to desired values,
and set ``index`` to 0.
Then call the :ref:`VIDIOC_SUBDEV_ENUM_FRAME_SIZE` ioctl with a pointer to the
structure.

A successful call will return with minimum and maximum frame sizes filled in.
Repeat with increasing ``index`` until ``EINVAL`` is received.
``EINVAL`` means that either no more entries are available in the enumeration,
or that an input parameter was invalid.

Sub-devices that only support discrete frame sizes (such as most
sensors) will return one or more frame sizes with identical minimum and
maximum values.

Not all possible sizes in given [minimum, maximum] ranges need to be
supported. For instance, a scaler that uses a fixed-point scaling ratio
might not be able to produce every frame size between the minimum and
maximum values. Applications must use the
:ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>` ioctl to try the
sub-device for an exact supported frame size.

Available frame sizes may depend on the current 'try' formats at other

Annotation

Implementation Notes