7.45. ioctl VIDIOC_PREPARE_BUF¶
VIDIOC_PREPARE_BUF - Prepare a buffer for I/O
ioctl(int fd, VIDIOC_PREPARE_BUF, struct v4l2_buffer *argp)¶
- File descriptor returned by open().
- Pointer to struct
Applications can optionally call the ioctl VIDIOC_PREPARE_BUF ioctl to
pass ownership of the buffer to the driver before actually enqueuing it,
using the ioctl VIDIOC_QBUF, VIDIOC_DQBUF ioctl, and to prepare it for future I/O. Such
preparations may include cache invalidation or cleaning. Performing them
in advance saves time during the actual I/O. In case such cache
operations are not required, the application can use one of
V4L2_BUF_FLAG_NO_CACHE_CLEAN flags to skip the respective step.
v4l2_buffer structure is specified in
7.45.5. 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.
- File I/O is in progress.
- The buffer
typeis not supported, or the
indexis out of bounds, or no buffers have been allocated yet, or the