ioctl VIDIOC_G_CTRL, VIDIOC_S_CTRL &manvol; VIDIOC_G_CTRL VIDIOC_S_CTRL Get or set the value of a control int ioctl int fd int request struct v4l2_control *argp fd &fd; request VIDIOC_G_CTRL, VIDIOC_S_CTRL argp To get the current value of a control applications initialize the 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 the id and value fields of a struct v4l2_control and call the VIDIOC_S_CTRL ioctl. When the id is invalid drivers return an &EINVAL;. When the value is out of bounds drivers can choose to take the closest valid value or return an &ERANGE;, whatever seems more appropriate. However, VIDIOC_S_CTRL is a write-only ioctl, it does not return the actual new value. These ioctls work only with user controls. For other control classes the &VIDIOC-G-EXT-CTRLS;, &VIDIOC-S-EXT-CTRLS; or &VIDIOC-TRY-EXT-CTRLS; must be used. &cs-str; __u32 id Identifies the control, set by the application. __s32 value New value or current value. &return-value; EINVAL The &v4l2-control; id is invalid. ERANGE The &v4l2-control; value is out of bounds. EBUSY The control is temporarily not changeable, possibly because another applications took over control of the device function this control belongs to.