OS X and iOS Kernel Programming

Notifications from the Driver

The methods that we have implemented in the sample driver's user client are designed to be blocking functions; that is, the user process does not continue execution until the user client has completed the requested operation. For example, the method in our user client DelayForMs() would suspend the thread on which it was called until the specified delay has elapsed. While this may not be a bad thing for a function whose aim is to explicitly delay the calling thread, a user space application may not always wish to wait for a driver operation to complete, particularly if that operation may take an indeterminate amount of time or is dependent on an event over which the driver has no control, such as the arrival of data ...