switch_dev_register函数demo

#include<linux/init.h>
#include<linux/module.h>
#include <linux/switch.h>
#include <linux/device.h>

static struct switch_dev switch_data;

static ssize_t inquire_state_show(struct device *dev,struct device_attribute *attr, char *buf)  
{  
	return sprintf(buf, "%u\n", switch_data.state);
} 

static ssize_t change_state_store(struct device *dev,struct device_attribute *attr, const char *buf, size_t count)
{
        unsigned long val;
        int ret;
        ret = kstrtoul(buf, 10, &val);
        if (ret < 0) {
               dev_err(dev, "couldn't parse string %d\n", ret);
               return ret;
        }
	switch_set_state(&switch_data,val);
        return count;
}

static DEVICE_ATTR_RO(inquire_state); 
static DEVICE_ATTR_WO(change_state);

static int switch_init(void)
{
	  int ret;
	  switch_data.name = "www";
	  switch_data.index = 0;
	  switch_data.state = 0;
	  ret = switch_dev_register(&switch_data);
	  if(ret)
	  {
	  	printk("switch_dev_register returned:%d!\n", ret);
		return ret;
	  }
	  ret = device_create_file(switch_data.dev, &dev_attr_inquire_state);
          ret = device_create_file(switch_data.dev, &dev_attr_change_state);
	  printk("switch_init ok\n");
	  return 0;
}
		
static void switch_exit(void)
{
	printk("switch_exit!");
} 

module_init(switch_init);
module_exit(switch_exit);
MODULE_LICENSE("Dual BSD/GPL");