7.66. V4L2 open()¶
v4l2-open - Open a V4L2 device
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_NONBLOCKflag is given, the
read()function and the VIDIOC_DQBUF ioctl will return the
EAGAINerror 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 support the
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
7.66.5. Return Value¶
open() returns the new file descriptor. On error
-1 is returned, and the
errno 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.