Method query_ctrl

src/usbio.rs:103–126

(&self, id: u32)

    }

    fn query_ctrl(&self, id: u32) -> Result<V4l2CtrlRange, Errno> {
        let dev = &self.0;
        let mut qctrl = v4l2_queryctrl {
            id,
            ..Default::default()
        };

        unsafe {
            match vidioc_queryctrl(dev.as_raw_fd(), &mut qctrl) {
                Ok(_) => {
                    if qctrl.flags & V4L2_CTRL_FLAG_DISABLED != 0 {
                        return Err(errno::Errno(22)); // EINVAL
                    }
                    Ok(V4l2CtrlRange {
                        minimum: qctrl.minimum,
                        maximum: qctrl.maximum,
                        step: qctrl.step,
                        default_value: qctrl.default_value,
                    })
                }
                _ => Err(errno::Errno(errno())),
            }
        }
    }
}

pub(crate) fn open_camera(hint: &str) -> Result<CameraHandle, crate::Error> {