V4L2 ioctl() &manvol; v4l2-ioctl Program a V4L2 device #include <sys/ioctl.h> int ioctl int fd int request void *argp fd &fd; 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. The 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 . &return-value; When an ioctl that takes an output or read/write parameter fails, the parameter remains unmodified.