threeeye
bc1d038eac
Squashed backup commit (no shallow-clone history issues) of xiaomi-mt6833-dev/kernel_xiaomi_mt6833 (lineage-23.2 branch, upstream commit 9eece662e) plus all fixes applied to get everpal_defconfig building clean against a modern (GCC 15.2.0) toolchain -- see the previous commit message on the lineage-23.2 branch (also in this repo history is not available here since this is a squashed snapshot; full incremental history lives in the local DL380 checkout and the upstream GitHub remote). Upstream: https://github.com/xiaomi-mt6833-dev/kernel_xiaomi_mt6833 (lineage-23.2)
35 lines
1.4 KiB
ReStructuredText
35 lines
1.4 KiB
ReStructuredText
.. -*- coding: utf-8; mode: rst -*-
|
|
|
|
.. _querycap:
|
|
|
|
*********************
|
|
Querying Capabilities
|
|
*********************
|
|
|
|
Because V4L2 covers a wide variety of devices not all aspects of the API
|
|
are equally applicable to all types of devices. Furthermore devices of
|
|
the same type have different capabilities and this specification permits
|
|
the omission of a few complicated and less important parts of the API.
|
|
|
|
The :ref:`VIDIOC_QUERYCAP` ioctl is available to
|
|
check if the kernel device is compatible with this specification, and to
|
|
query the :ref:`functions <devices>` and :ref:`I/O methods <io>`
|
|
supported by the device.
|
|
|
|
Starting with kernel version 3.1, :ref:`VIDIOC_QUERYCAP`
|
|
will return the V4L2 API version used by the driver, with generally
|
|
matches the Kernel version. There's no need of using
|
|
:ref:`VIDIOC_QUERYCAP` to check if a specific ioctl
|
|
is supported, the V4L2 core now returns ``ENOTTY`` if a driver doesn't
|
|
provide support for an ioctl.
|
|
|
|
Other features can be queried by calling the respective ioctl, for
|
|
example :ref:`VIDIOC_ENUMINPUT` to learn about the
|
|
number, types and names of video connectors on the device. Although
|
|
abstraction is a major objective of this API, the
|
|
:ref:`VIDIOC_QUERYCAP` ioctl also allows driver
|
|
specific applications to reliably identify the driver.
|
|
|
|
All V4L2 drivers must support :ref:`VIDIOC_QUERYCAP`.
|
|
Applications should always call this ioctl after opening the device.
|