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- .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
- .. c:namespace:: V4L
- .. _func-ioctl:
- ************
- V4L2 ioctl()
- ************
- Name
- ====
- v4l2-ioctl - Program a V4L2 device
- Synopsis
- ========
- .. code-block:: c
- #include <sys/ioctl.h>
- ``int ioctl(int fd, int request, void *argp)``
- Arguments
- =========
- ``fd``
- File descriptor returned by :c:func:`open()`.
- ``request``
- V4L2 ioctl request code as defined in the ``videodev2.h`` header
- file, for example VIDIOC_QUERYCAP.
- ``argp``
- Pointer to a function parameter, usually a structure.
- Description
- ===========
- The :ref:`ioctl() <func-ioctl>` function is used to program V4L2 devices. The
- argument ``fd`` must be an open file descriptor. An ioctl ``request``
- has encoded in it whether the argument is an input, output or read/write
- parameter, and the size of the argument ``argp`` in bytes. Macros and
- defines specifying V4L2 ioctl requests are located in the
- ``videodev2.h`` header file. Applications should use their own copy, not
- include the version in the kernel sources on the system they compile on.
- All V4L2 ioctl requests, their respective function and parameters are
- specified in :ref:`user-func`.
- Return Value
- ============
- On success 0 is returned, on error -1 and the ``errno`` variable is set
- appropriately. The generic error codes are described at the
- :ref:`Generic Error Codes <gen-errors>` chapter.
- When an ioctl that takes an output or read/write parameter fails, the
- parameter remains unmodified.
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