7.66. V4L2 open()¶

7.66.1. Name¶

v4l2-open - Open a V4L2 device

7.66.2. Synopsis¶

#include <fcntl.h>

int open(const char *device_name, int flags)¶

7.66.3. Arguments¶

device_name

Device to be opened.

flags

Open flags. Access mode must be O_RDWR. This is just a technicality, input devices still support only reading and output devices only writing.

When the 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 support the O_NONBLOCK flag.

Other flags have no effect.

7.66.4. Description¶

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 undefined state.

7.66.5. Return Value¶

On success open() returns the new file descriptor. On error -1 is returned, and the errno variable is set appropriately. Possible error codes are:

EACCES: The caller has no permission to access the device.
EBUSY: The driver does not support multiple opens and the device is already in use.
ENXIO: No device corresponding to this device special file exists.
ENOMEM: Not enough kernel memory was available to complete the request.
EMFILE: The process already has the maximum number of files open.
ENFILE: The limit on the total number of files open on the system has been reached.