irqreturn_t s2io_isr (int irq, void * dev_id, struct pt_regs * regs);
This function is the ISR handler of the device. It identifies the reason for the interrupt and calls the relevant service routines. As a contongency measure, this ISR allocates the recv buffers, if their numbers are below the panic value which is presently set to 25% of the original number of rcv buffers allocated.
will be returned if IRQ was handled by this routine
will be returned if interrupt is not from our device