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button.c
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button.c
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#include <linux/init.h>
#include <linux/module.h>
#include <linux/gpio.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
MODULE_LICENSE("Dual BSD/GPL");
#define LED 17
#define BTN 18
int irqNum;
static inline void set_led(void){
gpio_set_value(LED, 1);
}
static inline void clr_led(void){
gpio_set_value(LED, 0);
}
static irqreturn_t irq_handler(int irq, void *dev_id, struct pt_regs *regs){
printk(KERN_INFO "irq handler called\n");
if(gpio_get_value(BTN)){
set_led();
}else{
clr_led();
}
return IRQ_HANDLED;
}
static int __init test_init(void){
printk(KERN_INFO "Loading module\n");
gpio_request(BTN, "BTN");
gpio_request(LED, "LED");
gpio_direction_input(BTN);
gpio_direction_output(LED, 0);
printk(KERN_INFO "Setup GPIOs\n");
if((irqNum = gpio_to_irq(BTN)) < 0){
printk(KERN_INFO "Error getting irq number.\n");
gpio_free(BTN);
gpio_free(LED);
return 0;
}
printk(KERN_INFO "Got irq number\n");
if(request_irq(irqNum, (irq_handler_t ) irq_handler, IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING, "button handler", NULL) < 0){
printk(KERN_INFO "Error while making irq request\n");
gpio_free(BTN);
gpio_free(LED);
return 0;
}
printk(KERN_INFO "Finished loading.\n");
return 0;
}
static void __exit test_exit(void){
printk(KERN_INFO "Goodbye, world!\n");
gpio_free(LED);
gpio_free(BTN);
free_irq(irqNum, NULL);
}
module_init(test_init);
module_exit(test_exit);