         deviceInfo.identifier = identifier
         
         guard withUnsafeMutablePointer(to: &deviceInfo, {
-            IOControl(fileDescriptor, HCI.IOCTL.GetDeviceInfo, UnsafeMutableRawPointer($0)) }) == 0
+            IOControl(fileDescriptor, HCI.IOCTL.GetDeviceInfo, UnsafeMutableRawPointer($0)) == 0 })
             else { throw POSIXError.fromErrno() }
         
         return deviceInfo
     }
     
+    /// List all HCI devices.
     func deviceList() throws -> HCIDeviceList {
         
         // allocate HCI device list buffer

        deviceList.numberOfDevices = UInt16(HCI.maximumDeviceCount)
        
        // request device list
        let ioctlValue = withUnsafeMutablePointer(to: &deviceList) {
            IOControl(fileDescriptor, HCI.IOCTL.GetDeviceList, $0)
        }
        guard ioctlValue >= 0 else { throw POSIXError.fromErrno() }
        
        return deviceList
    }

            else { throw POSIXError.fromErrno() }
    }
    
    /// Close the HCI device.
    func disable(_ identifier: HostController.Identifier) throws {
        
        guard IOControl(fileDescriptor, HCI.IOCTL.DeviceDown, CInt(identifier)) >= 0
            else { throw POSIXError.fromErrno() }
    }
    
    /// Get device information.
    func deviceInformation(_ identifier: HostController.Identifier) throws -> HCIDeviceInformation {
        
