VIDIOC_G_CTRL, VIDIOC_S_CTRL — Get or set the value of a control
File descriptor returned by
To get the current value of a control applications
id field of a struct
v4l2_control and call the
VIDIOC_G_CTRL ioctl with a pointer to this
structure. To change the value of a control applications initialize
fields of a struct v4l2_control and call the
id is invalid drivers
return an EINVAL error code. When the
value is out
of bounds drivers can choose to take the closest valid value or return
an ERANGE error code, whatever seems more appropriate. However,
VIDIOC_S_CTRL is a write-only ioctl, it does not
return the actual new value. If the
is inappropriate for the control (e.g. if it refers to an unsupported
menu index of a menu control), then EINVAL error code is returned as well.
Table A.52. struct v4l2_control
|__u32||Identifies the control, set by the application.|
|__s32||New value or current 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 struct v4l2_control
is out of bounds.
The control is temporarily not changeable, possibly because another applications took over control of the device function this control belongs to.
Attempt to set a read-only control or to get a write-only control.