Documentation/userspace-api/media/v4l/vidioc-querycap.rst

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

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System
Linux kernel
Corpus path
Documentation/userspace-api/media/v4l/vidioc-querycap.rst
Extension
.rst
Size
10962 bytes
Lines
290
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_QUERYCAP:

*********************
ioctl VIDIOC_QUERYCAP
*********************

Name
====

VIDIOC_QUERYCAP - Query device capabilities

Synopsis
========

.. c:macro:: VIDIOC_QUERYCAP

``int ioctl(int fd, VIDIOC_QUERYCAP, struct v4l2_capability *argp)``

Arguments
=========

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

``argp``
    Pointer to struct :c:type:`v4l2_capability`.

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

All V4L2 devices support the ``VIDIOC_QUERYCAP`` ioctl. It is used to
identify kernel devices compatible with this specification and to obtain
information about driver and hardware capabilities. The ioctl takes a
pointer to a struct :c:type:`v4l2_capability` which is
filled by the driver. When the driver is not compatible with this
specification the ioctl returns an ``EINVAL`` error code.

.. c:type:: v4l2_capability

.. tabularcolumns:: |p{1.4cm}|p{2.8cm}|p{13.1cm}|

.. cssclass:: longtable

.. flat-table:: struct v4l2_capability
    :header-rows:  0
    :stub-columns: 0
    :widths:       3 4 20

    * - __u8
      - ``driver``\ [16]
      - Name of the driver, a unique NUL-terminated ASCII string. For
	example: "bttv". Driver specific applications can use this
	information to verify the driver identity. It is also useful to
	work around known bugs, or to identify drivers in error reports.

	Storing strings in fixed sized arrays is bad practice but
	unavoidable here. Drivers and applications should take precautions
	to never read or write beyond the end of the array and to make
	sure the strings are properly NUL-terminated.
    * - __u8
      - ``card``\ [32]
      - Name of the device, a NUL-terminated UTF-8 string. For example:
	"Yoyodyne TV/FM". One driver may support different brands or
	models of video hardware. This information is intended for users,
	for example in a menu of available devices. Since multiple TV
	cards of the same brand may be installed which are supported by
	the same driver, this name should be combined with the character

Annotation

Implementation Notes