Implementing an interrupt handler

Inside the kernel, an interrupt handler is a function associated with a CPU interrupt line (or pin) that Linux executes whenever the peripheral connected with this line changes the pin status; when this happens, an interrupt request is generated for the CPU, and it's captured by the kernel, which in turn executes the proper handler.

In this recipe, we will see how to install an interrupt handler which the kernel executes each time an interrupt occurs on a well-defined line.

Getting ready

The simplest code to implement an interrupt handler is the code in linux/drivers/misc/dummy-irq.c. Here is the handler:

static int irq = -1;

static irqreturn_t dummy_interrupt(int irq, void *dev_id)
{
...