7.64. ioctl VIDIOC_SUBDEV_G_CLIENT_CAP, VIDIOC_SUBDEV_S_CLIENT_CAP

7.64.1. Name

VIDIOC_SUBDEV_G_CLIENT_CAP - VIDIOC_SUBDEV_S_CLIENT_CAP - Get or set client capabilities.

7.64.2. Synopsis

VIDIOC_SUBDEV_G_CLIENT_CAP

int ioctl(int fd, VIDIOC_SUBDEV_G_CLIENT_CAP, struct v4l2_subdev_client_capability *argp)

VIDIOC_SUBDEV_S_CLIENT_CAP

int ioctl(int fd, VIDIOC_SUBDEV_S_CLIENT_CAP, struct v4l2_subdev_client_capability *argp)

7.64.3. Arguments

fd

File descriptor returned by open().

argp

Pointer to struct v4l2_subdev_client_capability.

7.64.4. Description

These ioctls are used to get and set the client (the application using the subdevice ioctls) capabilities. The client capabilities are stored in the file handle of the opened subdev device node, and the client must set the capabilities for each opened subdev separately.

By default no client capabilities are set when a subdev device node is opened.

The purpose of the client capabilities are to inform the kernel of the behavior of the client, mainly related to maintaining compatibility with different kernel and userspace versions.

The VIDIOC_SUBDEV_G_CLIENT_CAP ioctl returns the current client capabilities associated with the file handle fd.

The VIDIOC_SUBDEV_S_CLIENT_CAP ioctl sets client capabilities for the file handle fd. The new capabilities fully replace the current capabilities, the ioctl can therefore also be used to remove capabilities that have previously been set.

VIDIOC_SUBDEV_S_CLIENT_CAP modifies the struct v4l2_subdev_client_capability to reflect the capabilities that have been accepted. A common case for the kernel not accepting a capability is that the kernel is older than the headers the userspace uses, and thus the capability is unknown to the kernel.

type v4l2_subdev_client_capability

struct v4l2_subdev_client_capability

__u64

capabilities

Sub-device client capabilities of the opened device.

Client Capabilities

Capability	Description
V4L2_SUBDEV_CLIENT_CAP_STREAMS	The client is aware of streams. Setting this flag enables the use of ‘stream’ fields (referring to the stream number) with various ioctls. If this is not set (which is the default), the ‘stream’ fields will be forced to 0 by the kernel.
V4L2_SUBDEV_CLIENT_CAP_INTERVAL_USES_WHICH	The client is aware of the v4l2_subdev_frame_interval which field. If this is not set (which is the default), the which field is forced to V4L2_SUBDEV_FORMAT_ACTIVE by the kernel.

7.64.5. 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.

ENOIOCTLCMD

The kernel does not support this ioctl.