驱动支持select函数(2)

cdev_init(&dev_c,&globalvar_fops);
 
 
 
err = cdev_add(&dev_c,dev,1);
 
 
 
if(err)
 
{
 
printk(KERN_NOTICE "error %d adding FC_dev\n",err);
 
unregister_chrdev_region(dev, 1);
 
return err;
 
}
 
else
 
{
 
printk("device register success! \n");
 
}
 
 
 
cdev_class = class_create(THIS_MODULE,DEVICE_NAME);
 
if(IS_ERR(cdev_class))
 
{
 
printk("ERR:cannot create a cdev_class\n");
 
unregister_chrdev_region(dev, 1);
 
return -1;
 
}
 
device_create(cdev_class, NULL, dev, 0, DEVICE_NAME);
 
 
 
init_MUTEX(&sem);
 
init_waitqueue_head(&outq);
 
}
 
return ret;
 
}
 
 
 
 
 
static void __exit globalvar_exit(void)
 
{
 
device_destroy(cdev_class,dev);
 
class_destroy(cdev_class);
 
unregister_chrdev_region(dev,1);
 
printk("device ");
 
}
 
 
 
 
 
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)
 
{
 
if (down_interruptible(&sem))
 
{
 
return - ERESTARTSYS;
 
}
 
if (copy_from_user(&global_var, buf, sizeof(int)))
 
{
 
up(&sem);
 
return - EFAULT;
 
}
 
up(&sem);
 
flag = 1;
 
 
 
wake_up_interruptible(&outq);
 
 
 
return sizeof(int);
 
}
 
 
 
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;
 
} 
 
module_init(globalvar_init);
 
module_exit(globalvar_exit);