7.63. ioctl VIDIOC_SUBDEV_G_CLIENT_CAP, VIDIOC_SUBDEV_S_CLIENT_CAP¶
VIDIOC_SUBDEV_G_CLIENT_CAP - VIDIOC_SUBDEV_S_CLIENT_CAP - Get or set client capabilities.
int ioctl(int fd, VIDIOC_SUBDEV_G_CLIENT_CAP, struct v4l2_subdev_client_capability *argp)
int ioctl(int fd, VIDIOC_SUBDEV_S_CLIENT_CAP, struct v4l2_subdev_client_capability *argp)
File descriptor returned by open().
Pointer to struct
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.
VIDIOC_SUBDEV_G_CLIENT_CAP ioctl returns the current client capabilities
associated with the file handle
VIDIOC_SUBDEV_S_CLIENT_CAP ioctl sets client capabilities for the file
fd. The new capabilities fully replace the current capabilities, the
ioctl can therefore also be used to remove capabilities that have previously
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.
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.