1*4882a593Smuzhiyun.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2*4882a593Smuzhiyun.. c:namespace:: V4L 3*4882a593Smuzhiyun 4*4882a593Smuzhiyun.. _func-ioctl: 5*4882a593Smuzhiyun 6*4882a593Smuzhiyun************ 7*4882a593SmuzhiyunV4L2 ioctl() 8*4882a593Smuzhiyun************ 9*4882a593Smuzhiyun 10*4882a593SmuzhiyunName 11*4882a593Smuzhiyun==== 12*4882a593Smuzhiyun 13*4882a593Smuzhiyunv4l2-ioctl - Program a V4L2 device 14*4882a593Smuzhiyun 15*4882a593SmuzhiyunSynopsis 16*4882a593Smuzhiyun======== 17*4882a593Smuzhiyun 18*4882a593Smuzhiyun.. code-block:: c 19*4882a593Smuzhiyun 20*4882a593Smuzhiyun #include <sys/ioctl.h> 21*4882a593Smuzhiyun 22*4882a593Smuzhiyun``int ioctl(int fd, int request, void *argp)`` 23*4882a593Smuzhiyun 24*4882a593SmuzhiyunArguments 25*4882a593Smuzhiyun========= 26*4882a593Smuzhiyun 27*4882a593Smuzhiyun``fd`` 28*4882a593Smuzhiyun File descriptor returned by :c:func:`open()`. 29*4882a593Smuzhiyun 30*4882a593Smuzhiyun``request`` 31*4882a593Smuzhiyun V4L2 ioctl request code as defined in the ``videodev2.h`` header 32*4882a593Smuzhiyun file, for example VIDIOC_QUERYCAP. 33*4882a593Smuzhiyun 34*4882a593Smuzhiyun``argp`` 35*4882a593Smuzhiyun Pointer to a function parameter, usually a structure. 36*4882a593Smuzhiyun 37*4882a593SmuzhiyunDescription 38*4882a593Smuzhiyun=========== 39*4882a593Smuzhiyun 40*4882a593SmuzhiyunThe :ref:`ioctl() <func-ioctl>` function is used to program V4L2 devices. The 41*4882a593Smuzhiyunargument ``fd`` must be an open file descriptor. An ioctl ``request`` 42*4882a593Smuzhiyunhas encoded in it whether the argument is an input, output or read/write 43*4882a593Smuzhiyunparameter, and the size of the argument ``argp`` in bytes. Macros and 44*4882a593Smuzhiyundefines specifying V4L2 ioctl requests are located in the 45*4882a593Smuzhiyun``videodev2.h`` header file. Applications should use their own copy, not 46*4882a593Smuzhiyuninclude the version in the kernel sources on the system they compile on. 47*4882a593SmuzhiyunAll V4L2 ioctl requests, their respective function and parameters are 48*4882a593Smuzhiyunspecified in :ref:`user-func`. 49*4882a593Smuzhiyun 50*4882a593SmuzhiyunReturn Value 51*4882a593Smuzhiyun============ 52*4882a593Smuzhiyun 53*4882a593SmuzhiyunOn success 0 is returned, on error -1 and the ``errno`` variable is set 54*4882a593Smuzhiyunappropriately. The generic error codes are described at the 55*4882a593Smuzhiyun:ref:`Generic Error Codes <gen-errors>` chapter. 56*4882a593Smuzhiyun 57*4882a593SmuzhiyunWhen an ioctl that takes an output or read/write parameter fails, the 58*4882a593Smuzhiyunparameter remains unmodified. 59