fn set_device_status()

in src/devices/src/virtio/mmio.rs [165:217]
52 lines of code
11 McCabe index (conditional complexity)

    fn set_device_status(&mut self, status: u32) {
        use device_status::*;
        // match changed bits
        match !self.device_status & status {
            ACKNOWLEDGE if self.device_status == INIT => {
                self.device_status = status;
            }
            DRIVER if self.device_status == ACKNOWLEDGE => {
                self.device_status = status;
            }
            FEATURES_OK if self.device_status == (ACKNOWLEDGE | DRIVER) => {
                self.device_status = status;
            }
            DRIVER_OK if self.device_status == (ACKNOWLEDGE | DRIVER | FEATURES_OK) => {
                self.device_status = status;
                let device_activated = self.locked_device().is_activated();
                if !device_activated && self.are_queues_valid() {
                    self.locked_device()
                        .activate(self.mem.clone())
                        .expect("Failed to activate device");
                }
            }
            _ if (status & FAILED) != 0 => {
                // TODO: notify backend driver to stop the device
                self.device_status |= FAILED;
            }
            _ if status == 0 => {
                if self.locked_device().is_activated() {
                    let mut device_status = self.device_status;
                    let reset_result = self.locked_device().reset();
                    match reset_result {
                        Some((_interrupt_evt, mut _queue_evts)) => {}
                        None => {
                            device_status |= FAILED;
                        }
                    }
                    self.device_status = device_status;
                }

                // If the backend device driver doesn't support reset,
                // just leave the device marked as FAILED.
                if self.device_status & FAILED == 0 {
                    self.reset();
                }
            }
            _ => {
                warn!(
                    "invalid virtio driver status transition: 0x{:x} -> 0x{:x}",
                    self.device_status, status
                );
            }
        }
    }