Threaded IRQs

The main goal of threaded IRQs is to reduce the time spent with interrupts disabled to a bare minimum. With threaded IRQs, the way you register an interrupt handler is a bit simplified. You do not even have to schedule the bottom half yourself. The core does that for us. The bottom half is then executed in a dedicated kernel thread. We do not use request_irq() anymore, but request_threaded_irq():

int request_threaded_irq(unsigned int irq, irq_handler_t handler,\ 
                            irq_handler_t thread_fn, \ 
                            unsigned long irqflags, \ 
                            const char *devname, void *dev_id) 
 

The request_threaded_irq() function accepts two functions in its parameters:

• @handler function: This is the same function as the one registered with request_irq(). It represents the top-half function, which runs in an atomic context (or hard-IRQ). If it can process the interrupt faster so that you can get rid of the bottom half at all, it should...