aaa.c

Linux可供用户空间和内核空间相互访问的字符设备驱动程序代码。

//#define MODULE
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <asm/uaccess.h>
#include <linux/wait.h>
#include <asm/semaphore.h>
#include <linux/poll.h>

#define MAJOR_NUM 254

MODULE_LICENSE("GPL");
static ssize_t globalvar_read(struct file *, char *, size_t, loff_t*);
static ssize_t globalvar_write(struct file *, const char *, size_t, loff_t*);
static unsigned int globalvar_poll(struct file *, poll_table *);
static loff_t globalvar_llseek(struct file *filp, loff_t fake1, int fake2);
//added by madongchao 20071118 for switch chip
extern void bm8024_interruptTest(void);
//added end

struct file_operations globalvar_fops =
{
  read: globalvar_read, 
  write: globalvar_write,
  poll: globalvar_poll,
  //added by madongchao 20071118 for switch chip
  llseek: globalvar_llseek,
  //added end
};

//static int global_var = 0;
static struct semaphore sem;
static wait_queue_head_t outq;
static int flag = 0;

static int __init globalvar_init(void)
{
  int ret;

  //added by madongchao for test 20071117
  printk("globalvar_init : get in!\n");
  //added end
  ret = register_chrdev(MAJOR_NUM, "globalvar", &globalvar_fops);
  if (ret)
  {
    printk("globalvar register failure");
   }
  else
  {
    printk("globalvar register success");
    init_MUTEX(&sem);
    init_waitqueue_head(&outq);
  }
  return ret;
}

static void __exit globalvar_exit(void)
{
  int ret;
  ret = unregister_chrdev(MAJOR_NUM, "globalvar");
  if (ret)
  {
   printk("globalvar unregister failure");
  }
  else
  {
   printk("globalvar unregister success");
   }
}
//changed by madongchao 20071027 for 软件平台的消息触发机制
static ssize_t globalvar_read(struct file *filp, char *buf, size_t len, loff_t *off)
{
	if (down_interruptible(&sem))
	{ 
		return - ERESTARTSYS;
	}
   	flag = 0;
	up(&sem);
   	return sizeof(int);
}

static ssize_t globalvar_write(struct file *filp, const char *buf, size_t len,loff_t *off)
{   
	printk("in globalvar_write\n");
	
	if (down_interruptible(&sem))
	{ 
		return - ERESTARTSYS;
	}
	
   	flag = 1;
	wake_up_interruptible(&outq);
	up(&sem);
   	return sizeof(int);
}
#if 0
static ssize_t globalvar_read(struct file *filp, char *buf, size_t len, loff_t *off)
{
  /*if (wait_event_interruptible(outq, flag != 0))
  {
    return - ERESTARTSYS;
  }*/

  if (down_interruptible(&sem))
  { 
    return - ERESTARTSYS;
   }
   flag = 0;
  if (__copy_to_user(buf, &global_var, sizeof(int)))
   {
    up(&sem); 
    return - EFAULT;
    }
   up(&sem);
   return sizeof(int);
}

static ssize_t globalvar_write(struct file *filp, const char *buf, size_t len,loff_t *off)
{   
   printk("hhh\n");
   if (down_interruptible(&sem))
   {
    return - ERESTARTSYS;
    }
   if (__copy_from_user(&global_var, buf, sizeof(int)))
   {
    up(&sem);
    return - EFAULT;
    } 
  
   
    wake_up_interruptible(&outq);
    up(&sem); 

   flag = 1;
   return sizeof(int);
}
#endif
//changed end

static unsigned int globalvar_poll(struct file *filp, poll_table *wait)
{
  unsigned int mask = 0;
  poll_wait(filp, &outq, wait);
  if (flag != 0)
  {
    mask|=POLLIN | POLLRDNORM;

   }
  return mask;

}

//added by madongchao 20071118 for switch chip
loff_t globalvar_llseek(struct file *filp, loff_t fake1, int fake2)
{	
	bm8024_interruptTest();
	return 15;
}
//added end


module_init(globalvar_init);
module_exit(globalvar_exit);