1. 代码

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

#define NEWCHRDEV_NAME        "newChrLed"
#define NEWCHRDEV_COUNT        1

#define LED_MAJOR             200 //主设备号
#define LED_NAME              "led"

/* 寄存器的物理地址 */
#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)

#if 1
/* 地址映射后的虚拟地址指针 */ //iomem是虚拟地址的类型
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   /* 关灯 */
#define LEDON       1   /* 开灯 */
#endif

/* 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;        /* 类 */
    struct device *device;      /* 设备 */
    int major;                  /* 主设备号 */
    int minor;                  /* 次设备号 */
};

static struct newchrled_dev newchrled; /* led设备 */


/* 驱动开闭读写 */
/* LED灯打开或者关闭 */
static 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)
{
    /* 在这里添加私有数据 */
    filp->private_data = &newchrled;
    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 ssize_t newchrled_write(struct file *filp, const char __user *buf,
                         size_t count, loff_t *ppos)
{
    int retValue;
    unsigned char dataBuf[1]; /* 1表示1位，开灯关灯 */

    retValue = copy_from_user(dataBuf, buf, count);
    if(retValue < 0){
        printk("kernel write failed! \r\n");
        return -EFAULT;
    }

    /* 判断开灯还是关灯 */
    led_switch(dataBuf[0]);

    return 0;
}

static const struct file_operations newchrled_fops = {
    .owner   = THIS_MODULE,
    .open    = newchrled_open,
    .write   = newchrled_write,
    .release = newchrled_release
};

static void led_init(void)
{
    /* 初始化LED灯 */
    int val;
    /* 1.1 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);

    /* 1.2 初始化 */
    val = readl(IMX6U_CCM_CCGR1);
    val &= ~(3 << 26);                  /* 先清楚以前的bit26  27 */
    val |= 3 << 26;                     /* 26 27 置1 */
    writel(val, IMX6U_CCM_CCGR1);

    /* 1.3 设置 GPIO1_IO03 的复用功能，将其复用为
    * GPIO1_IO03，最后设置 IO 属性。
    */
    writel(0x5, SW_MUX_GPIO1_IO03);     /* 设置复用 */
    writel(0x10B0, SW_PAD_GPIO1_IO03);  /* 设置电气属性 */

    /* 1.4 设置 GPIO1_IO03 为输出功能 */
    val = readl(GPIO1_GDIR);
    val &= ~(1 << 3);                  
    val |= 1 << 3;                    
    writel(val, GPIO1_GDIR);

    /* 1.5 默认开启 LED */
    val = readl(GPIO1_DR);
    val &= ~(1 << 3); 
    writel(val, GPIO1_DR);
}

/* 驱动入口 */
static int __init newchrled_init(void)
{   
    unsigned int ret = 0;
    
    /* 1.初始化LED */
    led_init();
    printk("led init success \r\n");

    /* 2.分配设备号 */
    newchrled.major = 0; /* 手动申请0,表示需要分配 */
    if(newchrled.major){
        newchrled.devId = MKDEV(newchrled.major, 0);
        ret = register_chrdev_region(newchrled.devId, 
                                     NEWCHRDEV_COUNT, 
                                     NEWCHRDEV_NAME);/* 主设备号，申请1个，名字 */ 
    } else {
        ret = alloc_chrdev_region(&newchrled.devId, 0, 
                                  NEWCHRDEV_COUNT, 
                                  NEWCHRDEV_NAME);/* 注意第一个参数是取地址，次设备号是0 */
        newchrled.major = MAJOR(newchrled.devId);
        newchrled.minor = MINOR(newchrled.devId);
    }

    if(ret < 0){
        printk("chrdev region error \r\n");
        goto fail_devId;
    }

    printk("major = %d, minor = %d\r\n", newchrled.major, newchrled.minor);
    
    /* 3.注册字符设备 */
    newchrled.cDev.owner = THIS_MODULE;
    cdev_init(&newchrled.cDev, &newchrled_fops); /* cdev初始化 */
    ret = cdev_add(&newchrled.cDev, newchrled.devId, NEWCHRDEV_COUNT);
    if(ret < 0){
        goto fail_cdev;
    }
    printk("register chrdev success \r\n");

    /* 4.自动创建设备节点 */
    newchrled.class = class_create(THIS_MODULE, NEWCHRDEV_NAME);
    if(IS_ERR(newchrled.class)){
        ret = PTR_ERR(newchrled.class);
        goto fail_class;
    }
    printk("create class success \r\n");
    
    /* 5. 创建之后要创建设备*/
    /* 下面函数
     * 第一个参数代表本类，第二个参数代表父类
     * 第三个参数是dev_t
     * 第四个参数是设备可能会使用一些数据，一般null
     * 第五个参数是fint，=xxx 会创建/dev/xxx
     * */
    newchrled.device = device_create(newchrled.class, 
                                    NULL, newchrled.devId, NULL, 
                                    NEWCHRDEV_NAME); 
    if(IS_ERR(newchrled.device)){
        ret = PTR_ERR(newchrled.device);
        goto fail_device;
    }

    printk("create device success \r\n");

    printk("module init... \r\n");
    return 0;

fail_device:
    class_destroy(newchrled.class); /* 这块出问题了，表示前面都没出问题, 所以把前面释放t */
fail_class:
    cdev_del(&newchrled.cDev);
fail_cdev:
    unregister_chrdev_region(newchrled.devId, NEWCHRDEV_COUNT);
fail_devId:
    return ret;
}
/* 驱动出口 */
static void __exit newchrled_exit(void)
{
    /* 1.删除字符设备 */
    cdev_del(&newchrled.cDev);
    printk("delete chrdev success \r\n");
    
    /* 2.注销设备号 */
    unregister_chrdev_region(newchrled.devId, NEWCHRDEV_COUNT);
    printk("unregister chrdev success \r\n");

    /* 3.先摧毁设备再摧毁类 */
    device_destroy(newchrled.class, newchrled.devId);
    printk("device destroy success \r\n");

    /* 4.摧毁类 */
    class_destroy(newchrled.class);
    printk("class destroy success \r\n");
    
    printk("module exit \r\n");
}

/* 注册和卸载驱动 */
module_init(newchrled_init);
module_exit(newchrled_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Shao Zheming");