.. Permission is granted to copy, distribute and/or modify this .. document under the terms of the GNU Free Documentation License, .. Version 1.1 or any later version published by the Free Software .. Foundation, with no Invariant Sections, no Front-Cover Texts .. and no Back-Cover Texts. A copy of the license is included at .. Documentation/media/uapi/fdl-appendix.rst. .. .. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections .. _func-ioctl: ************ V4L2 ioctl() ************ Name ==== v4l2-ioctl - Program a V4L2 device Synopsis ======== .. code-block:: c #include .. c:function:: int ioctl( int fd, int request, void *argp ) :name: v4l2-ioctl Arguments ========= ``fd`` File descriptor returned by :ref:`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() ` 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 ` chapter. When an ioctl that takes an output or read/write parameter fails, the parameter remains unmodified.