1. 子系统位platform   /sys/devices/platform/att_test
lrwxrwxrwx 1 root root    0 2014-05-17 10:04 driver -> ../../../bus/platform/drivers/att_test
-r--r--r-- 1 root root 4096 2014-05-17 10:05 modalias
drwxr-xr-x 2 root root    0 2014-05-17 10:05 power
lrwxrwxrwx 1 root root    0 2014-05-17 10:04 subsystem -> ../../../bus/platform
-rwxrwxrwx 1 root root 4096 2014-05-17 10:05 test
-rw-r--r-- 1 root root 4096 2014-05-17 10:05 uevent

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/kobject.h>
#include <linux/platform_device.h>

struct att_dev{
	struct platform_device *pdev;
	struct kobject *kobj;
};

static struct att_dev *dev = NULL;

static ssize_t att_store(struct device *dev,
					struct device_attribute *attr,
					const char *buf, size_t count)
{
	printk("echo debug buf\n");

	return count;
}

static ssize_t att_show(struct device *dev,
                 struct device_attribute *attr,