Detaching an interrupt handler

When done with the ISR, we may wish to break the association between the ISR and the interrupt vector:

int
InterruptDetach (int id);

I said may because threads that handle interrupts are generally found in servers, and servers generally hang around forever. It's therefore conceivable that a well-constructed server wouldn't ever issue the InterruptDetach() function call. Also, the OS will remove any interrupt handlers that a thread or process may have associated with it when the thread or process dies. So, simply falling off the end of main(), calling exit(), or exiting due to a SIGSEGV, will dissociate your ISR from the interrupt vector, automagically. (Of course, you'll probably want to handle this a little better, and stop your device from generating interrupts. If another device is sharing the interrupt, then there are no two ways about it—you must clean up, otherwise you won't get any more interrupts if running in edge-sensitive mode, or you'll get a constant flood of ISR dispatches if running in level-sensitive mode.)

Continuing the above example, if we want to detach, we'd use the following code:

void
terminateInterrupts (void)
{
    InterruptDetach (interruptID);
}

If this was the last ISR associated with that interrupt vector, the kernel would automatically mask the interrupt source at the PIC level so that it doesn't generate interrupts.