字符设备驱动-LED实验

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

int major;

static struct class *leddrv_class;

static struct class_device *leddrv_class_dev;

volatile unsigned long *gpfcon = NULL;

volatile unsigned long *gpfdat = NULL;

static int led_drv_open(struct inode *inode, struct file *file)

{

//printk("first_drv_open\n");

*gpfcon &= ~((0x3<(4*2)) | (0x3<(5*2)) | (0x3<(6*2)));

*gpfcon |= ((0x1<(4*2)) | (0x1<(5*2)) | (0x1<(6*2)));

return 0;

}

static ssize_t led_drv_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos)

{

char val = 0;

copy_from_user(&val,buf,count);

if(val == 1)

*gpfdat &= ~((1<4) | (1<5) | (1<6));

else if(val == 0)

*gpfdat |= ((1<4) | (1<5) | (1<6));

//printk("first_drv_write\n");

return 0;

}

static struct file_operations led_drv_fops = {

.owner = THIS_MODULE,

.open = led_drv_open,

.write = led_drv_write,

};

static int led_drv_init(void)

{

major = register_chrdev(0, "led_drv", &led_drv_fops); // 注册, 告诉内核

leddrv_class = class_create(THIS_MODULE, "leddrv");

leddrv_class_dev = class_device_create(leddrv_class, NULL, MKDEV(major, 0), NULL, "xxx");

gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);

gpfdat = gpfcon + 1;

return 0;

}

static void led_drv_exit(void)

{

unregister_chrdev(major, "led_drv"); // 卸载

class_device_unregister(leddrv_class_dev);

class_destroy(leddrv_class);

iounmap(gpfcon);

}

module_init(led_drv_init);

module_exit(led_drv_exit);

MODULE_LICENSE("GPL");

==================================================================================================

测试程序：

#include

#include

#include

#include

int main(int argc, char **argv)

{

int fd;

int val = 1;

fd = open("/dev/xxx",O_RDWR);

if(fd < 0)

{

printf("cant open!\n");

}

if(argc != 2)

{

printf("Usage:\n");

printf("%s ",argv[0]);

return 0;

}

if(strcmp(argv[1],"on") == 0)

val = 1;

else

val = 0;

write(fd,&val,4);

return 0;

}

==================================================================================================

注：在调用write(fd,&val,4);时根据不同的val值在调用驱动程序时做出判断：关闭、打开led灯

copy_from_user(&val,buf,count); //从用户空间buf拷贝count长度的数据到内核空间val中

copy_to_user(buf，&val,,count); //从内核空间val拷贝count长度的数据到用户空间buf中

内核空间不能直接访问物理地址,故要映射：

gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);