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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/userspace-api/media/v4l/querycap.rst | |
parent | Initial commit. (diff) | |
download | linux-upstream/5.10.209.tar.xz linux-upstream/5.10.209.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | Documentation/userspace-api/media/v4l/querycap.rst | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/v4l/querycap.rst b/Documentation/userspace-api/media/v4l/querycap.rst new file mode 100644 index 000000000..15a90271a --- /dev/null +++ b/Documentation/userspace-api/media/v4l/querycap.rst @@ -0,0 +1,34 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later + +.. _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. |