# SetDataServicedHandler Installs the handler block to execute when data is removed from the queue. ``` virtual kern_return_t SetDataServicedHandler(OSAction *action); ``` ## Parameters `action` The [`OSAction`](/documentation/DriverKit/OSAction) object that contains the callback method to execute. The data queue retains your action object until you install a new handler or cancel the dispatch source. The system executes your callback on the dispatch queue you designated in your [`OSAction`](/documentation/DriverKit/OSAction) object. ## Return Value [`kIOReturnSuccess`](/documentation/DriverKit/kIOReturnSuccess) on success, or another value if an error occurs. See [Error Codes](/documentation/DriverKit/error-codes). ## Discussion If your code produces data for the queue, use this method to install a handler so you can add more data to the queue. When space becomes available in the queue, the system executes your handler. --- Copyright © 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)