编写LED驱动-设备树

写LED驱动 

首先，我们要建立一个file_operator结构体：

/* 定义自己的file_operations结构体                                              */
static struct file_operations led_drv = {
    .owner     = THIS_MODULE,       //主设备号
    .open    = led_drv_open,　　　　 // driver function
    .read    = led_drv_read,
    .write   = led_drv_write,
    .release = led_drv_close,
};

编写相应的四个driver function:

/* 3. 实现对应的open/read/write等函数，填入file_operations结构体                   */
static ssize_t led_drv_read (struct file *file, char __user *buf, size_t size, loff_t *offset)
{
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    return 0;
}

/* write(fd, &val, 1); */
static ssize_t led_drv_write (struct file *file, const char __user *buf, size_t size, loff_t *offset)
{
    int err;
    char status;
    //struct inode *inode = file_inode(file);
    //int minor = iminor(inode);
    
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    err = copy_from_user(&status, buf, 1);

    /* 根据次设备号和status控制LED */
    gpiod_set_value(led_gpio, status);
    
    return 1;
}

static int led_drv_open (struct inode *node, struct file *file)
{
    //int minor = iminor(node);
    
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    /* 根据次设备号初始化LED */
    gpiod_direction_output(led_gpio, 0);
    
    return 0;
}

static int led_drv_close (struct inode *node, struct file *file)
{
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    return 0;
}

注册filer_operator: 告诉CPU：这里采用设备树的方式：

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