1. 多按键支持
2. 按键访问应用程序设计

相关代码

#include <linux/module.h>
#include <linux/init.h>
#include <linux/miscdevice.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/fs.h>
#include <linux/uaccess.h>

#define GPFCON 0x56000050
#define GPFDAT 0x56000054

struct work_struct *work1;

struct timer_list key_timer ;
unsigned int * gpio_data;
unsigned int key_num;

void work1_func(struct work_struct *work)
{
    //printk("key down \n");
    //启动定时器
    //jiffies 是linux是全局变量，表示现在的时间（滴答数）
    mod_timer(&key_timer，jiffies + HZ/10);//HZ是1s，这里超时是100ms
}

void key_timer_func(unsigned long delta)
{
    unsigned short data ;
    data = readw(gpio_data)&0x01 ;
    if( data == 0 ){
        printk("key4 down \n");
        key_num = 4;
    }
    
    data = readw(gpio_data)&0x04 ;
    if( data == 0 ){
        printk("key3 down \n");
        key_num = 3;
    }
}

irqreturn_t key_int(int irq , void * dev_id)
{
    //提交下半部
    schedule_work(work1);
    return 0;
}

void key_hw_init()
{
    unsigned int * gpio_config;
    unsigned short data;
    gpio_config = ioremap(GPFCON,4);
    data = readw(gpio_config);
    data &= ~0b110011;
    data |=  0b100010;
    writew(data,gpio_config);
    gpio_data = ioremap(GPFDAT,4);
}

void key_open(struct inode *node, struct file *filp)
{
    return 0 ;
}

ssize_t key_read(struct file *filp,char __user *buf,size_t size,loff_t *pos)
{
    copy_to_user(buf,key_num,4);

}

struct file_operations key_fops={
    .open = key_open,
    .read = key_read，
};

struct miscdevice key_miscdev = {
    .minor = 200,
    .name  = "key",
    .fops  = &key_fops,
};

static int button_init()
{
    misc_register(&key_miscdev);
    //注册中断处理程序
    request_irq(IRQ_EINT0,key_init,IRQF_TRIGGER_FALLING,"key",0); //K4
    request_irq(IRQ_EINT2,key_init,IRQF_TRIGGER_FALLING,"key",0); //K3
    //按键初始化
    key_hw_init();
    //创建工作
    work1 = kmalloc(sizeof(struct work_struct),GFP_KERNEL);
    INIT_WORK(work1,work1_func);
    //初始化定时器
    init_timer(&key_timer);
    //key_timer.expires  = 10 ;
    key_timer.function = key_timer_func ;
    
    //注册定时器
    add_timer(&key_timer);
    return 0 ;
}

static void button_exit()
{
    misc_deregister(&key_miscdev);
}

module_init(button_init);
module_exit(button_exit);

三、按键访问应用程序

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int fd,key_num;
    //1.打开设备
    fd = open("/dev/2440key",0);
    if(fd < 0){
        printf("open device fail!\n");
    }
    
    //2.读取设备
    read(fd,&key_num,4);
    printf("key is %d\n",key_num);
    
    //3.关闭设备
    close(fd);

}

四、创建设备文件

mknod /dev/2440key c 10 200 // 主设备号10（混杂设备），次设备号200， c是字符设备。