i.MX6U-driver development-3-new character driver

1.New character drive principle

1.because in betweenregister_dev函数注册字符设备,The device number was wasted many times,And you need to manually specify the major device number

2.使用alloc_chrdev_region函数自动申请,register_chrdev_region函数手动申请

3.释放的时候使用unregister_chrdev_region

4.There are also updates for character devices,使用cdev结构体表示字符设备,然后用cdev_init初始化,Sum utilizationcdev_add进行添加

 

2.自动创建设备节点

The solution does not require manual settingsmknod设置节点,利用udev机制实现,busybox提供了udev简化版本mdev

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include<linux/cdev.h>
#include<linux/device.h>

#define NEWCHRLED_NAME "newchrled"
#define NEWCHRLED_COUNT 1


   




//寄存器物理地址
#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)

//虚拟地址
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;


#define LEDOFF 0
#define LEDON  1


//led设备结构体
struct newchrled_dev{
    struct cdev cdev;//字符设备
    dev_t devid;//设备号
    struct class *class;
    struct device *device;
    int major;//主设备号
    int minor;//次设备号
};

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_release(struct inode *inode, struct file *filp)
{
	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!\r\n");
		return -EFAULT;
	}

	ledstat = databuf[0];		/* 获取状态值 */

	if(ledstat == LEDON) {	
		led_switch(LEDON);		/* 打开LED灯 */
	} else if(ledstat == LEDOFF) {
		led_switch(LEDOFF);	/* 关闭LED灯 */
	}
	return 0;
}
static int newchrled_open(struct inode *inode, struct file *filp)
{
	filp->private_data = &newchrled; /* 设置私有数据 */
	return 0;
}
static struct file_operations newchrled_fops = {
	.owner = THIS_MODULE,
	.open = newchrled_open,
	.write = newchrled_write,
	.release = 	newchrled_release,    
};

//入口
static int __init newchrled_init(void)
{
    int ret=0;
    u32 val = 0;
    printk("newchrled_init success\r\n");
    //初始化led
    /* 初始化LED */
	/* 1、寄存器地址映射 */
  	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);

	/* 2、使能GPIO1时钟 */
	val = readl(IMX6U_CCM_CCGR1);
	val &= ~(3 << 26);	/* 清楚以前的设置 */
	val |= (3 << 26);	/* 设置新值 */
	writel(val, IMX6U_CCM_CCGR1);

	/* 3、设置GPIO1_IO03的复用功能,将其复用为
	 *    GPIO1_IO03,最后设置IO属性.
	 */
	writel(5, SW_MUX_GPIO1_IO03);
	
	/*寄存器SW_PAD_GPIO1_IO03设置IO属性
	 *bit 16:0 HYS关闭
	 *bit [15:14]: 00 默认下拉
     *bit [13]: 0 kepper功能
     *bit [12]: 1 pull/keeper使能
     *bit [11]: 0 关闭开路输出
     *bit [7:6]: 10 速度100Mhz
     *bit [5:3]: 110 R0/6驱动能力
     *bit [0]: 0 低转换率
	 */
	writel(0x10B0, SW_PAD_GPIO1_IO03);

	/* 4、设置GPIO1_IO03为输出功能 */
	val = readl(GPIO1_GDIR);
	val &= ~(1 << 3);	/* 清除以前的设置 */
	val |= (1 << 3);	/* 设置为输出 */
	writel(val, GPIO1_GDIR);

	/* 5、默认关闭LED */
	val = readl(GPIO1_DR);
	val |= (1 << 3);	
	writel(val, GPIO1_DR);
    //Initialize the device number
    if(newchrled.major)
    {
        newchrled.devid=MKDEV(newchrled.major,0);
        ret=register_chrdev_region(newchrled.devid,NEWCHRLED_COUNT,NEWCHRLED_NAME);

    }
    else
    {
        ret=alloc_chrdev_region(&newchrled.devid,0,NEWCHRLED_COUNT,NEWCHRLED_NAME);//Minor number slave address0申请1个
        newchrled.major=MAJOR(newchrled.devid);
        newchrled.minor=MINOR(newchrled.devid);
    }
    if(ret<0)
    {
        printk("newchrled_region error\r\n");
        return -1;
    }
    printk("newchrled major=%d,minor=%d\r\n",newchrled.major,newchrled.minor);
    //注册字符设备
    newchrled.cdev.owner =THIS_MODULE;
    cdev_init(&newchrled.cdev ,&newchrled_fops);
    cdev_add(&newchrled.cdev ,newchrled.devid,NEWCHRLED_COUNT);

    //自动创建设备节点
    //创建类
    newchrled.class = class_create(THIS_MODULE, NEWCHRLED_NAME);
	if (IS_ERR(newchrled.class))
		return PTR_ERR(newchrled.class);

    //节点
    newchrled.device=device_create( newchrled.class,NULL,newchrled.devid,NULL,NEWCHRLED_NAME);
	if (IS_ERR(newchrled.device))
		return PTR_ERR(newchrled.device);

    return 0;
}

//出口
static void __exit newchrled_exit(void)
{
    printk("newchrled_exit success\r\n");
	/* 取消映射 */
	iounmap(IMX6U_CCM_CCGR1);
	iounmap(SW_MUX_GPIO1_IO03);
	iounmap(SW_PAD_GPIO1_IO03);
	iounmap(GPIO1_DR);
	iounmap(GPIO1_GDIR);
    //删除字符设备
    cdev_del(&newchrled.cdev);
    //注销
    unregister_chrdev_region(newchrled.devid,NEWCHRLED_COUNT);
    //摧毁设备
    device_destroy(newchrled.class,newchrled.devid);
    //摧毁类
    class_destroy(newchrled.class);
}



//注册驱动
module_init(newchrled_init);
module_exit(newchrled_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("liujiasen");

3.文件私有数据

1.在openSet private data inside

filp->private_data = &newchrled; /* 设置私有数据 */