# IOTimerDispatchSource A dispatch source that notifies your driver at a specific time. ``` class IOTimerDispatchSource; ``` ## Overview An [`IOTimerDispatchSource`](/documentation/DriverKit/IOTimerDispatchSource) object executes an associated action at a designated time. After configuring the dispatch source object, call the [`WakeAtTime`](/documentation/DriverKit/IOTimerDispatchSource/WakeAtTime) method to schedule the time at which to execute your code. There are several timebases you can use to configure the timer, but the most common one is [`kIOTimerClockMachAbsoluteTime`](/documentation/DriverKit/kIOTimerClockMachAbsoluteTime). ## Topics ### Configuring the Timer Source [`static kern_return_t Create(IODispatchQueue *queue, IOTimerDispatchSource **source);`](/documentation/DriverKit/IOTimerDispatchSource/Create) Creates and configures a timer dispatch object. [`virtual bool init();`](/documentation/DriverKit/IOTimerDispatchSource/init) Handles the basic initialization of the dispatch source. [`virtual void free();`](/documentation/DriverKit/IOTimerDispatchSource/free) Performs any final cleanup for the timer dispatch source. [`virtual kern_return_t SetHandler(OSAction *action);`](/documentation/DriverKit/IOTimerDispatchSource/SetHandler) Sets the handler block to run when the timer fires. ### Rescheduling the Timer [`virtual kern_return_t WakeAtTime(uint64_t options, uint64_t deadline, uint64_t leeway);`](/documentation/DriverKit/IOTimerDispatchSource/WakeAtTime) Schedules a callback from the timer. [Clock Types](/documentation/DriverKit/3242783-clock_types) Clock types to use when configuring a timer. ### Starting and Stopping the Timer Source [`virtual kern_return_t SetEnableWithCompletion(bool enable, IODispatchSourceCancelHandler handler);`](/documentation/DriverKit/IOTimerDispatchSource/SetEnableWithCompletion) Enables or disables the timer. [`virtual kern_return_t Cancel(IODispatchSourceCancelHandler handler);`](/documentation/DriverKit/IOTimerDispatchSource/Cancel) Cancels all callbacks from the event source. ### Declaring Actions [`virtual void TimerOccurred(OSAction *action, uint64_t time);`](/documentation/DriverKit/IOTimerDispatchSource/TimerOccurred) Executes custom code when the timer fires. [`virtual kern_return_t CheckForWork(bool synchronous);`](/documentation/DriverKit/IOTimerDispatchSource/CheckForWork) Checks for events to handle. ## Relationships ### Inherits From [`IODispatchSource`](/documentation/DriverKit/IODispatchSource) --- 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)