Orange Pi5 kernel

^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  1) .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  2) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  3) .. _querycap:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  4) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  5) *********************
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  6) Querying Capabilities
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  7) *********************
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  8) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  9) Because V4L2 covers a wide variety of devices not all aspects of the API
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) are equally applicable to all types of devices. Furthermore devices of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) the same type have different capabilities and this specification permits
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) the omission of a few complicated and less important parts of the API.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) The :ref:`VIDIOC_QUERYCAP` ioctl is available to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) check if the kernel device is compatible with this specification, and to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) query the :ref:`functions <devices>` and :ref:`I/O methods <io>`
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) supported by the device.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) Starting with kernel version 3.1, :ref:`VIDIOC_QUERYCAP`
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) will return the V4L2 API version used by the driver, with generally
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) matches the Kernel version. There's no need of using
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) :ref:`VIDIOC_QUERYCAP` to check if a specific ioctl
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) is supported, the V4L2 core now returns ``ENOTTY`` if a driver doesn't
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) provide support for an ioctl.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) Other features can be queried by calling the respective ioctl, for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) example :ref:`VIDIOC_ENUMINPUT` to learn about the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) number, types and names of video connectors on the device. Although
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) abstraction is a major objective of this API, the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) :ref:`VIDIOC_QUERYCAP` ioctl also allows driver
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) specific applications to reliably identify the driver.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) All V4L2 drivers must support :ref:`VIDIOC_QUERYCAP`.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) Applications should always call this ioctl after opening the device.