Linux Device Driver for counting keyboard strokes

For each key pressed on the keyboard, it generates two interrupts (pressed and release).

Code:

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/interrupt.h>
	#include <linux/delay.h>
	MODULE_LICENSE("GPL");
	static int irq = 1, dev = 0xaa, counter = 0;
	static irqreturn_t keyboard_handler(int irq, void *dev)
	{
	pr_info("Keyboard Counter:%d\n", counter++);
	return IRQ_NONE;
	}
	/* registering irq */
	static int test_interrupt_init(void)
	{
	pr_info("%s: In init\n", __func__);
	return request_irq(irq, keyboard_handler, IRQF_SHARED,"my_keyboard_handler", &dev);
	}
	static void test_interrupt_exit(void)
	{
	pr_info("%s: In exit\n", __func__);
	synchronize_irq(irq); /* synchronize interrupt */
	free_irq(irq, &dev);
	}
	module_init(test_interrupt_init);
	module_exit(test_interrupt_exit);

view raw interrupt.c hosted with ❤ by GitHub

Output:

Notes:

1. IRQ line 1 is assigned for keyboard, we register our handler to be called on keyboard interrupt by calling request_irq
2. IRQF_SHARED flag is used for sharing the keyboard interrupt
3. synchronize_irq waits for the specific handler to exit.