<!--
{
  "availability" : [
    "DriverKit: 19.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "USBSerialDriverKit",
  "identifier" : "/documentation/USBSerialDriverKit/IOUserUSBSerial/Start",
  "metadataVersion" : "0.1.0",
  "role" : "Instance Method",
  "symbol" : {
    "kind" : "Instance Method",
    "modules" : [
      "USBSerialDriverKit"
    ],
    "preciseIdentifier" : "c:@S@IOUserUSBSerial@F@Start#*$@S@IOService#"
  },
  "title" : "Start"
}
-->

# Start

Starts the service for the specified provider.

```
virtual kern_return_t Start(IOService *provider);
```

## Parameters

`provider`

The provider object that matches the current service. Cast this object to the class you expect. The system retains this object for the duration of your `start` method. The system continues to retain the object if your service starts successfully, releasing it only after calling your service’s <doc://com.apple.documentation/documentation/SerialDriverKit/IOUserSerial/Stop> method.

## Return Value

<doc://com.apple.documentation/documentation/DriverKit/kIOReturnSuccess> on success, or another value if an error occurs. See <doc://com.apple.documentation/documentation/DriverKit/error-codes>.

## Discussion

After successfully matching the specified `provider` to your driver’s service, the system instantiates your service object and calls this method. Use this method to perform any additional configuration of your driver. For example, you might store a reference to the specified provider object for later use. When your service is configured, call the <doc://com.apple.documentation/documentation/DriverKit/IOService/RegisterService> method to let the system know that your service is running. Always call `super` early in your implementation of this method.

You don’t need to open a communications channel to your device in this method. The system calls your service’s <doc://com.apple.documentation/documentation/SerialDriverKit/IOUserSerial/HwActivate> method separately to activate your hardware.

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)