Generating Interrupts

Generating Interrupts

A driver has to call the Frame Scheduler interrupt handler from within the driver's interrupt handler using code similar to that shown in Example 7-11. This handler is entered concurrently on each CPU where the master or a synchronized Frame Scheduler is running. It delivers the interrupt to the Frame Scheduler on that CPU. The function to be invoked is

void frs_handle_driverintr(void);

It is possible for an interrupt handler to be entered at a time when the Frame Scheduler for its processor is not active; that is, after frs_destroy() has been called and before the driver termination function has been entered. The frs_handle_driverintr() function checks for this and does nothing when nothing is required.

Example 7-11 : Generating an Interrupt From a Device Driver

void example_intr()
{
   /*
   ** Step 1: anything required by the hardware
   */
   /*
   ** Step 2: if connected to the Frame Scheduler, send
   ** an interrupt to it. Flag FRS_is_active is set in
   ** Example 7-9 and cleared in Example 7-10.
   */
   if (FRS_is_active) frs_handle_driverintr();
   /*
   ** Step 3: any additional processing needed.
   */
   return;
}