1.在驱动中添加sysfs文件结点

static ssize_t backlight_store(struct device *dev,
		struct device_attribute *attr,
		const char *buf, size_t count)
{
    
    
	struct data *data = dev_get_drvdata(dev);
	int ret;
	int level;
	u8 write_buf[4];
	u8 command[4];

	ret = kstrtoint(buf,10,&level);//10表示10进制
	if(ret < 0)
	{
    
    
		dev_err(&data->client->dev,"%s failed\n");
		return -EINVAL;
	}
	

	if(level < 1 || level > 100)
	{
    
    
		dev_err(&data->client->dev,"%s,level %d unsupported",__func__,level);
		return -EINVAL;
	}
  
​````
	
	return count;
}

static DEVICE_ATTR(backlight_control,S_IWUSR,NULL,gac_ts_backlight_store);


//最后一项必须以NUll结尾
static struct attribute *sysfs_attrs[] = {
    
    
	&dev_attr_backlight_control.attr,
	NULL,
};

static const struct attribute_group attr_grp = {
    
    
	   .attrs = sysfs_attrs,
};

static int bl_probe(struct i2c_client *client,
					   const struct i2c_device_id *id)
{
    
    
 ···

	sysfs_create_group(&client->dev.kobj,&attr_grp); 
	
	````

}

生成的结点为：

/sys/devices/platform/soc/4a84000.i2c/i2c-0/0-0030/backlight_control

2.修改结点权限

在device/qcom(平台)/XXX(项目名)/init.target.rc中添加

#backlight control
chown root system /sys/devices/platform/soc/4a84000.i2c/i2c-0/0-0030/backlight_control
chmod 0666 /sys/devices/platform/soc/4a84000.i2c/i2c-0/0-0030/backlight_control