Add basic interrupt registration.

linux_driver/arduino_i2c.c

 #include <linux/module.h>
-#include <linux/kernel.h>
+
 #include <linux/gpio.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
 
+#define IRQ_GPIO_PIN	22
+#define GPIO_IRQ_NAME	"ai2c_keyboard_irq"
+
+static int irq_num = -1;
+static int count = 0;
+
+static irqreturn_t
+ai2c_intr_lower(int irq, void *data) {
+	if (count++ < 10) {
+		printk("ai2c_intr_lower:  entered\n");
+	}
+	return IRQ_HANDLED;
+}
 
 int
 ai2c_init(void) {
-	int i;
+	int ret;
+	int flags = 0;
+	void *drv_info = NULL;
 
 	printk(KERN_INFO "Arduino I2C Keyboard Starting\n");
-	for (i = 20; i < 35; i++) {
-		int g;
+	ret = gpio_request(IRQ_GPIO_PIN, GPIO_IRQ_NAME);
+	if (ret < 0) {
+		printk(KERN_ERR "ai2c:  IRQ pin reservation failed:  error %d\n", ret);
+		return ret;
+	}
+
+	gpio_direction_input(IRQ_GPIO_PIN);
+	irq_num = gpio_to_irq(IRQ_GPIO_PIN);
 
-		g = gpio_to_irq(i);
-		printk(KERN_INFO "ai2c:  gpio[%d]:  irq = %d\n", i, g);
+	printk(KERN_INFO "ai2c:  Reserved pin [%d]:  irq = %d\n", IRQ_GPIO_PIN, irq_num);
+
+	ret = request_irq(irq_num, ai2c_intr_lower, flags, "ai2c_keyboard", drv_info);
+	if (ret < 0) {
+		printk(KERN_ERR "ai2c:  request_irq failed:  error %d\n", ret);
+		return ret;
 	}
 
-	/*
-	 * A non 0 return means init_module failed; module can't be loaded.
-	 */
+	irq_set_irq_type(irq_num, IRQ_TYPE_EDGE_FALLING);
+
 	return 0;
 }
 
 void
 ai2c_shutdown(void) {
 	printk(KERN_INFO "Arduino I2C Keyboard Shutting Down\n");
+	if (irq_num > 0) {
+		free_irq(irq_num, ai2c_intr_lower);
+	}
 }
 
 module_init(ai2c_init);