Linux驱动编程【新驱动框架】

目录

一、新字符设备驱动原理

        1、以前的缺点

        2、int alloc_chrdev_region函数

        3、int register_chrdev_region函数

        4、卸载驱动

        5、字符设备注册 初始化cdev然后添加到Linux内核

二、自动创建设备节点

三、文件私有数据

四、实验程序与应用程序编写

一、新字符设备驱动原理

        1、以前的缺点

        使用register_chrdev函数注册字符设备，浪费了很多的次设备号，而且需要我们自 己手动指定主设备号

        2、int alloc_chrdev_region函数

        如果没有指定设备号的话就是用这个函数来申请设备号

        int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count, const char *name)

        3、int register_chrdev_region函数

        如果给定了设备的主设备号和次设备号就使用这个函数来注册设备号即可，一般是给定主设备号，使用MKDEV构建完整的dev_t，一般次设备号选择0

例子：

int major;
int minior;
dev_t devid;

if(major) {
    devid = MKDEV(major,0);
    register_chrdev_region(devid, 1, "test");
} else {
    allco_chedev_degion(&devid, 0, 1, "test");
    major = MAJOR(devid);
    minor = MINOR(devid);
}

        实际的驱动编写，考虑要完善，要考虑两种情况：①、给定设备号 ②、未给定设备号

        4、卸载驱动

使用unregister_chrdev_region函数释放前面申请的设备号

        5、字符设备注册 初始化cdev然后添加到Linux内核

        初始化一个cdev：cdev_init(&newchrled.cdev, &newchrled_fops);

        添加一个cdev：cdev_add(&newchrled.cdev, newchrled.devid, NEWCHRLED_CNT);

        注销一个cdev：cdev_del(&newchrled.cdev);

二、自动创建设备节点

        mdev是busybox提供的一个工具，用在嵌入式系统中，相当于简化版的udev，作用是在系统启动和热插拔或动态加载驱动程序时，自动创建设备节点。文件系统中的/dev目录下的设备节点都是由mdev创建的。

        在加载驱动过程中，根据驱动程序，在/dev下自动创建设备节点。

        ①、初始化class：newchrled.class =

                class_create(THIS_MODULE, NEWCHRLED_NAME);

        ②、创建一个设备节点：newchrled.device =

                device_create(newchrled.class, NULL, newchrled.devid,NULL, NEWCHRLED_NAME);

        ③、注销class和device 先注销device后注销class

                device_destroy(newchrled.class, newchrled.devid);

                class_destroy(newchrled.class);

三、文件私有数据

        filp->private_data = &newchrled; 可以在文件内直接访问设备成员信息

四、实验程序与应用程序编写

#include 

#include 

#include 

#include 

#include 

#include 

#include 

#include 

#include 

#include 



#include 

#include 

#include 





#define NEWCHRLED_CNT			1		  	

#define NEWCHRLED_NAME			"newchrled"	

#define LEDOFF 					0			

#define LEDON 					1			

 



#define CCM_CCGR1_BASE				(0x020C406C)	

#define SW_MUX_GPIO1_IO03_BASE		(0x020E0068)

#define SW_PAD_GPIO1_IO03_BASE		(0x020E02F4)

#define GPIO1_DR_BASE				(0x0209C000)

#define GPIO1_GDIR_BASE				(0x0209C004)





static void __iomem *IMX6U_CCM_CCGR1;

static void __iomem *SW_MUX_GPIO1_IO03;

static void __iomem *SW_PAD_GPIO1_IO03;

static void __iomem *GPIO1_DR;

static void __iomem *GPIO1_GDIR;





struct newchrled_dev{

	dev_t devid;			

	struct cdev cdev;		

	struct class *class;	

	struct device *device;	

	int major;				

	int minor;				



};



struct newchrled_dev newchrled;	





void led_switch(u8 sta)

{

	u32 val = 0;

	if(sta == LEDON) {

		val = readl(GPIO1_DR);

		val &= ~(1 << 3);	

		writel(val, GPIO1_DR);

	}else if(sta == LEDOFF) {

		val = readl(GPIO1_DR);

		val|= (1 << 3);	

		writel(val, GPIO1_DR);

	}	

}


static int newchrled_open(struct inode *inode, struct file *filp)

{

	filp->private_data = &newchrled;

	return 0;

}





static ssize_t newchrled_write(struct file *filp, const char __user *buf, size_t cnt, loff_t *offt)

{

	int retvalue;

	unsigned char databuf[1];

	unsigned char ledstat;



	retvalue = copy_from_user(databuf, buf, cnt);

	if(retvalue < 0) {

		printk("kernel write failed!rn");

		return -EFAULT;

	}



	ledstat = databuf[0];		



	if(ledstat == LEDON) {	

		led_switch(LEDON);		

	} else if(ledstat == LEDOFF) {

		led_switch(LEDOFF);	

	}

	return 0;

}




static int newchrled_release(struct inode *inode, struct file *filp)

{

	struct newchrled_dev *dev = (struct newchrled_dev *)filp->private_data;

	return 0;

}





static struct file_operations newchrled_fops = {

	.owner = THIS_MODULE,

	.open = newchrled_open,

	.write = newchrled_write,

	.release = 	newchrled_release,

};



static int __init newchrled_init(void)

{

	u32 val = 0;



	

	

  	IMX6U_CCM_CCGR1 = ioremap(CCM_CCGR1_BASE, 4);

	SW_MUX_GPIO1_IO03 = ioremap(SW_MUX_GPIO1_IO03_BASE, 4);

  	SW_PAD_GPIO1_IO03 = ioremap(SW_PAD_GPIO1_IO03_BASE, 4);

	GPIO1_DR = ioremap(GPIO1_DR_BASE, 4);

	GPIO1_GDIR = ioremap(GPIO1_GDIR_BASE, 4);



	

	val = readl(IMX6U_CCM_CCGR1);

	val &= ~(3 << 26);	

	val |= (3 << 26);	

	writel(val, IMX6U_CCM_CCGR1);



	

	writel(5, SW_MUX_GPIO1_IO03);

	

	

	writel(0x10B0, SW_PAD_GPIO1_IO03);



	

	val = readl(GPIO1_GDIR);

	val &= ~(1 << 3);	

	val |= (1 << 3);	

	writel(val, GPIO1_GDIR);



	

	val = readl(GPIO1_DR);

	val |= (1 << 3);	

	writel(val, GPIO1_DR);



	

	

	if (newchrled.major) {		

		newchrled.devid = MKDEV(newchrled.major, 0);

		register_chrdev_region(newchrled.devid, NEWCHRLED_CNT, NEWCHRLED_NAME);

	} else {						

		alloc_chrdev_region(&newchrled.devid, 0, NEWCHRLED_CNT, NEWCHRLED_NAME);	

		newchrled.major = MAJOR(newchrled.devid);	

		newchrled.minor = MINOR(newchrled.devid);	

	}

	printk("newcheled major=%d,minor=%drn",newchrled.major, newchrled.minor);	

	

	

	newchrled.cdev.owner = THIS_MODULE;

	cdev_init(&newchrled.cdev, &newchrled_fops);

	

	

	cdev_add(&newchrled.cdev, newchrled.devid, NEWCHRLED_CNT);



	

	newchrled.class = class_create(THIS_MODULE, NEWCHRLED_NAME);

	if(IS_ERR(newchrled.class)) {

		return PTR_ERR(newchrled.class);

	}

	

	newchrled.device = device_create(newchrled.class, NULL, newchrled.devid,

									NULL, NEWCHRLED_NAME);

	if(IS_ERR(newchrled.device)) {

		return PTR_ERR(newchrled.device);

	}

	return 0;

}


static void __exit newchrled_exit(void)

{

	int val;

	

	val = readl(GPIO1_DR);

	val |= (1 << 3);	

	writel(val, GPIO1_DR);

	

	iounmap(IMX6U_CCM_CCGR1);

	iounmap(SW_MUX_GPIO1_IO03);

	iounmap(SW_PAD_GPIO1_IO03);

	iounmap(GPIO1_DR);

	iounmap(GPIO1_GDIR);



	

	cdev_del(&newchrled.cdev);

	unregister_chrdev_region(newchrled.devid, NEWCHRLED_CNT); 

	

	device_destroy(newchrled.class, newchrled.devid);

	

	class_destroy(newchrled.class);



}

module_init(newchrled_init);

module_exit(newchrled_exit);

MODULE_LICENSE("GPL");

MODULE_AUTHOR("zhang");