v4l2-write — Write to a V4L2 device
#include <unistd.h>
ssize_t write( | int fd, |
| void *buf, | |
size_t count); |
write() writes up to
count bytes to the device referenced by the
file descriptor fd from the buffer starting at
buf. When the hardware outputs are not active
yet, this function enables them. When count is
zero, write() returns
0 without any other effect.
When the application does not provide more data in time, the previous video frame, raw VBI image, sliced VPS or WSS data is displayed again. Sliced Teletext or Closed Caption data is not repeated, the driver inserts a blank line instead.
On success, the number of bytes written are returned. Zero
indicates nothing was written. On error, -1
is returned, and the errno variable is set
appropriately. In this case the next write will start at the beginning
of a new frame. Possible error codes are:
Non-blocking I/O has been selected using the O_NONBLOCK flag and no
buffer space was available to write the data immediately.
fd is not a valid file
descriptor or is not open for writing.
The driver does not support multiple write streams and the device is already in use.
buf references an inaccessible
memory area.
The call was interrupted by a signal before any data was written.
I/O error. This indicates some hardware problem.
The write() function is not
supported by this driver, not on this device, or generally not on this
type of device.