Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst

Source file repositories/reference/linux-study-clean/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst

File Facts

System
Linux kernel
Corpus path
Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
Extension
.rst
Size
24201 bytes
Lines
554
Domain
Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: documentation
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

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

.. _VIDIOC_G_EXT_CTRLS:

******************************************************************
ioctl VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, VIDIOC_TRY_EXT_CTRLS
******************************************************************

Name
====

VIDIOC_G_EXT_CTRLS - VIDIOC_S_EXT_CTRLS - VIDIOC_TRY_EXT_CTRLS - Get or set the value of several controls, try control values

Synopsis
========

.. c:macro:: VIDIOC_G_EXT_CTRLS

``int ioctl(int fd, VIDIOC_G_EXT_CTRLS, struct v4l2_ext_controls *argp)``

.. c:macro:: VIDIOC_S_EXT_CTRLS

``int ioctl(int fd, VIDIOC_S_EXT_CTRLS, struct v4l2_ext_controls *argp)``

.. c:macro:: VIDIOC_TRY_EXT_CTRLS

``int ioctl(int fd, VIDIOC_TRY_EXT_CTRLS, struct v4l2_ext_controls *argp)``

Arguments
=========

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

``argp``
    Pointer to struct :c:type:`v4l2_ext_controls`.

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

These ioctls allow the caller to get or set multiple controls
atomically. Control IDs are grouped into control classes (see
:ref:`ctrl-class`) and all controls in the control array must belong
to the same control class.

Applications must always fill in the ``count``, ``which``, ``controls``
and ``reserved`` fields of struct
:c:type:`v4l2_ext_controls`, and initialize the
struct :c:type:`v4l2_ext_control` array pointed to
by the ``controls`` fields.

To get the current value of a set of controls applications initialize
the ``id``, ``size`` and ``reserved2`` fields of each struct
:c:type:`v4l2_ext_control` and call the
:ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` ioctl. String controls must also set the
``string`` field. Controls of compound types
(``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is set) must set the ``ptr`` field.

If the ``size`` is too small to receive the control result (only
relevant for pointer-type controls like strings), then the driver will
set ``size`` to a valid value and return an ``ENOSPC`` error code. You
should re-allocate the memory to this new size and try again. For the
string type it is possible that the same issue occurs again if the
string has grown in the meantime. It is recommended to call
:ref:`VIDIOC_QUERYCTRL` first and use
``maximum``\ +1 as the new ``size`` value. It is guaranteed that that is
sufficient memory.

N-dimensional arrays are set and retrieved row-by-row. You cannot set a

Annotation

Implementation Notes