Device to be opened.
Open flags. Access mode must be
O_RDWR. This is just a technicality, input devices
still support only reading and output devices only writing.
O_NONBLOCK flag is
given, the read() function and the
VIDIOC_DQBUF ioctl will return
the EAGAIN error code when no data is available or no buffer is in the driver
outgoing queue, otherwise these functions block until data becomes
available. All V4L2 drivers exchanging data with applications must
Other flags have no effect.
To open a V4L2 device applications call
open() with the desired device name. This
function has no side effects; all data format parameters, current
input or output, control values or other properties remain unchanged.
At the first
open() call after loading the driver
they will be reset to default values, drivers are never in an
open returns the new file
descriptor. On error -1 is returned, and the
variable is set appropriately. Possible error codes are:
The caller has no permission to access the device.
The driver does not support multiple opens and the device is already in use.
No device corresponding to this device special file exists.
Not enough kernel memory was available to complete the request.
The process already has the maximum number of files open.
The limit on the total number of files open on the system has been reached.