以下是驱动测试代码：

//内核的驱动代码

#include <linux/init.h>
#include <linux/module.h> //for module_init moudule_exit
#include <linux/fs.h> //for MKDEV register_chrdev_region
#include <linux/cdev.h> //字符设备头文件
#include <linux/device.h>
#include <asm/io.h> //for ioremap
#include <linux/platform_device.h> //for 平台设备
#include <linux/of.h>
#include <linux/signal.h>
#include <linux/interrupt.h>

#define LED_MA 500 //主设备号(那一类设备)
//某些主设备号已经静态地分配给了大部分公用设备。见Documentation/devices.txt 。 这里我们常使用250
#define LED_MI 2 //次设备号(这类设备当中的具体哪个设备)

//目标:把字符设备改造为平台设备
//1. 把硬件信息，分离出去，放到设备树
//#define LED3CON 0X11000C20
//#define LED3DAT 0x11000c24
struct resource *led_res_con;
struct resource *led_res_dat;

struct resource *key1_res; //devices source pointer

struct fasync_struct *async_queue; /* 异步结构体指针，用于读 */

struct cdev led; //定义一个字符设备
#define LED_MAGIC 'L' //幻数，类似加密，避免误操作
#define LED_ON _IOW(LED_MAGIC, 1, int)
#define LED_OFF _IOW(LED_MAGIC,2,int)

unsigned int *led3_con;
unsigned int *led3_dat;

int led_open (struct inode *inode, struct file *file)
{
led3_con = ioremap((phys_addr_t)led_res_con,1); //把硬件的物理地址转换为内核的虚拟地址
if(led3_con == NULL){
printk("led3_con ioremap fail\n");
return -1;
}
led3_dat = ioremap((phys_addr_t)led_res_dat,1);
if(led3_dat == NULL){
printk("led3_dat ioremap fail\n");
return -1;
}

writel((readl(led3_con) & (~0xf)) | 1,led3_con);//led3 and key2 had use same register;
writel(1,led3_dat);

printk("led_open ok\n");
return 0;
}

int led_release(struct inode *inode, struct file *file)
{
free_irq(key1_res->start, NULL);
printk("remove OK\n");

printk("led_release ok\n");

return 0;
}

//实现自定义的个性化操作
long led_ioctl(struct file *file, unsigned int cmd, unsigned long args)
{

switch(cmd) //解析ioctl 命令
{
case LED_ON: //点亮灯
printk("led on cmd=%d\n",cmd);
writel(1,led3_dat);
break;
case LED_OFF: //灭灯
printk("led off cmd=%d\n",cmd);
writel(0,led3_dat);
break;
default:
printk("ioctl cmd no found\n");
break;
}

printk("led_ioctl end\n");
return 0;
}

irqreturn_t key_interrupt(int irqno, void *devid)
{

kill_fasync(&async_queue, SIGIO, POLL_IN); //发送SIGIO 异步通知信号
printk("irqno = %d\n", irqno);
return IRQ_HANDLED;
}

int key_fasync (int fd,struct file *filp,int mode)
{
return fasync_helper(fd,filp,mode,&async_queue);//处理标志的变更
}

//3.实现设备的文件操作
struct file_operations fops={ //设备的文件操作
.owner = THIS_MODULE,
.open = led_open,
.release = led_release,
.unlocked_ioctl = led_ioctl,
.fasync = key_fasync,
};

int led_init(struct platform_device *pdev) //把找到的平台设备的信息传进来
{
int ret;
dev_t dev_id= MKDEV(LED_MA, LED_MI); //把主次设备号合并生成设备ID

//1.注册设备号
ret =register_chrdev_region(dev_id,1,"test_led");
if(ret<0){
printk("regiser led fail\n ");
return -1;
}

//2.初始化字符设备
cdev_init(&led,&fops); //字符设备初始化
ret =cdev_add(&led,dev_id,1); //添加字符设备到系统中
if(ret<0){
printk("cdev add led fail\n ");
return -1;
}

led_res_con = pdev->resource[0].start;
led_res_dat = pdev->resource[1].start;
printk("led init go 1\n");

/*****************************************************/
key1_res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
if (key1_res == NULL) {
printk("No resource !\n");
return -ENODEV;
}

ret = request_irq(key1_res->start, //硬件中断号 对应exynos4412-test4412.dts中test4412-key interrupts = <1 2>中的1
key_interrupt, //中断处理函数
key1_res->flags, //中断标志 IRQF_DISABLED 在表示中断处理时屏蔽掉其它所有中断
"key2", //中断名称 在cat /proc/interrupts 克看到
NULL);
if (ret < 0) {
printk("failed request irq: irqno = irq_res->start");
return ret;
}
printk("key irq init ok\n");
/*********************************************************/

return 0; //返回值为零表示运行成功 ，负值表示失败
}

void led_exit(void)
{

dev_t dev_id= MKDEV(LED_MA, LED_MI);
cdev_del(&led); //删除设备
unregister_chrdev_region(dev_id, 1); //取消注册
printk("led exit go\n");
}

//2.把内核模块的入口，改为platform_driver的入口
//module_init(led_init);
//module_exit(led_exit);

static const struct of_device_id machled[] = {
{ .compatible = "test,led3"}, //必须和设备树里的设备名字一样
{},
};

MODULE_DEVICE_TABLE(of, machled);

struct platform_driver led_platform_driver = {
.driver = {
.name = "test_led",
.owner = THIS_MODULE,
.of_match_table = of_match_ptr(machled),
},
.probe = led_init,
.remove = led_exit,
};

module_platform_driver(led_platform_driver); //声明led_platform_driver为平台设备驱动的加载入口

MODULE_LICENSE("Dual BSD/GPL");

接下来是测试代码：

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/stat.h>

#define LED_MAGIC 'L'

//#define LED_ON 1
//#define LED_OFF 2

#define LED_ON _IOW(LED_MAGIC, 1, int)
#define LED_OFF _IOW(LED_MAGIC,2,int)

int flag = 0;
void input_handler (int signum)
{

printf("receive a signal from globalfifo, signalnum : %d\n",signum);
flag = 1;

}

int main(int argc, char **argv)
{
int fd = open("/dev/led", O_RDWR);

if (fd < 0) {
printf("open /dev/led fail\n");
return -1;
}

int oflags;
signal(SIGIO, input_handler); //让input_handler()处理SIGIO信号
fcntl(fd, F_SETOWN, getpid()); //设置设备文件的所有者为本进程
oflags = fcntl(fd, F_GETFL); // 会调用 驱动中的 .fasync
fcntl(fd, F_SETFL, oflags | FASYNC); //FASYNC 设置支持异步通知模式

while(1)
{
sleep(100);
if (flag)
{
ioctl(fd, LED_OFF); //ioctl 实现设备的个性化操作（可自定义命令）
printf("LED_OFF\n"); //注意要加\n 否则打印信息可能没有

flag = 0;

}
}
}

最后测试下来还是有一些小问题，后续再看；