7.62.1. Name

VIDIOC_SUBDEV_QUERYCAP - Query sub-device capabilities

7.62.2. Synopsis


int ioctl(int fd, VIDIOC_SUBDEV_QUERYCAP, struct v4l2_subdev_capability *argp)

7.62.3. Arguments

File descriptor returned by open().
Pointer to struct v4l2_subdev_capability.

7.62.4. Description

All V4L2 sub-devices support the VIDIOC_SUBDEV_QUERYCAP ioctl. It is used to identify kernel devices compatible with this specification and to obtain information about driver and hardware capabilities. The ioctl takes a pointer to a struct v4l2_subdev_capability which is filled by the driver. When the driver is not compatible with this specification the ioctl returns ENOTTY error code.

struct v4l2_subdev_capability
__u32 version

Version number of the driver.

The version reported is provided by the V4L2 subsystem following the kernel numbering scheme. However, it may not always return the same version as the kernel if, for example, a stable or distribution-modified kernel uses the V4L2 stack from a newer kernel.

The version number is formatted using the KERNEL_VERSION() macro:

#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))

__u32 version = KERNEL_VERSION(0, 8, 1);

printf ("Version: %u.%u.%u\\n",

(version >> 16) & 0xFF, (version >> 8) & 0xFF, version & 0xFF);

__u32 capabilities Sub-device capabilities of the opened device, see Sub-Device Capabilities Flags.
__u32 reserved[14] Reserved for future extensions. Set to 0 by the V4L2 core.
Sub-Device Capabilities Flags
V4L2_SUBDEV_CAP_RO_SUBDEV 0x00000001 The sub-device device node is registered in read-only mode. Access to the sub-device ioctls that modify the device state is restricted. Refer to each individual subdevice ioctl documentation for a description of which restrictions apply to a read-only sub-device.

7.62.5. 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.

The device node is not a V4L2 sub-device.