8.2. V4L2 ioctl()¶
v4l2-ioctl - Program a V4L2 device
- File descriptor returned by open().
- V4L2 ioctl request code as defined in the
videodev2.hheader file, for example VIDIOC_QUERYCAP.
- Pointer to a function parameter, usually a structure.
The ioctl() function is used to program V4L2 devices. The
fd must be an open file descriptor. An ioctl
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 Function Reference.
8.2.5. 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
Generic Error Codes chapter.
When an ioctl that takes an output or read/write parameter fails, the parameter remains unmodified.