ARM-linux驱动学习：led驱动程序编写练习（2014-8-22）

LED驱动程序：led_dev.c

#include 
#include 
#include 
#include 
#include 

static volatile unsigned int *GPJ2CON,*GPJ2DAT;
static int major = 0;

static int led_open(struct inode *pi, struct file *pf)//主要用于初始化
{
        printk(" led driver file open.\n");
        *GPJ2CON &= 0xffff0000;
        *GPJ2CON |= 0x00001111;
        *GPJ2DAT |= 0x0f;
    
        return 0;
}


static int led_release(struct inode *pi, struct file *pf)
{
        printk(" test release.\n");
        return 0;
}

static ssize_t led_write(struct file *pf, const char __user *pbuf, size_t len, loff_t *ppos)
{
        char *after;
        int a = simple_strtol(pbuf,&after,16);
        *GPJ2DAT = ~a;


        return 4;
}


static ssize_t led_read(struct file *pf, char __user *pbuf, size_t len, loff_t *ppos)
{
        printk(" GPJ2DAT = %x\n",*GPJ2DAT);
        printk(" buf: %s",pbuf);
        return 0;
}


static struct file_operations led_fops =
{
        .owner     = THIS_MODULE,
        .open      = led_open,
        .release   = led_release,
        .write     = led_write,
        .read      = led_read,
};


static __init int test_init(void)
{
        major = register_chrdev(0, "LED", &led_fops);
        printk("major = %d\n",major);
        GPJ2CON = ioremap(0xe0200280, 8);
        GPJ2DAT = GPJ2CON + 1;
        printk("GPJ2CON:0x%p,GPJ2DAT:0x%p\n", GPJ2CON, GPJ2DAT);
        return 0;
}



static __exit void test_exit(void)
{
        iounmap(GPJ2CON);
        unregister_chrdev(major, "LED");
        *GPJ2DAT |= 0x0f;
        printk("\n      Goodbye!\n\n");
}


module_init(test_init);
module_exit(test_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("henry");
MODULE_DESCRIPTION("This is test demo");

在kernel/drivers/char下的Kconfig里面添加：

config LED
        tristate "LED DEV"
        default y

Makefile里面添加：obj-m  += led_dev.o

在kernel下编译：make menuconfig

                            make modules

把kernel/drivers/char下的led_dev.ko文件下载到开发板上：

tftp  -g  -r  led_dev.ko 192.168.x.x

在开发板上挂载该LED驱动模块：insmod  led_dev.ko

查看挂载的模块：          lsmod

查看设备：                    cat /proc/devices

创建字符设备：             mknod led c 251 1    (命令 设备名 类型 主设备号 次设备号)

通过echo写入内容：     echo  1  >  led

卸载模块：                    rmmod led_dev

应用程序：ledapp.c

#include 
#include     
#include     
#include 
#include 
#include 
#include 
int main(void)
{
        char buf[20];
        int fd; 
        fd = open("led",O_RDWR);
        while(1)
        {   
                fgets(buf,sizeof(buf),stdin);
                write(fd,buf,sizeof(buf));
                read(fd,buf,sizeof(buf));
        }   

        return 0;
}

编译应用程序：arm-none-linux-gnueabi-gcc -static ledapp.c -o ledapp            （-static添加静态库）

下载到开发板上并运行：./ledapp