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he message the device will give when asked */
static char Message[BUF_LEN];
/* How far did the process reading the message get?
* Useful if the message is larger than the size of the
* buffer we get to fill in device_read. */
static char *Message_Ptr;
/* This function is called whenever a process attempts
* to open the device file */
static int device_open(struct inode *inode,
struct file *file)
{
#ifdef DEBUG
printk ("device_open(%p)\n", file);
#endif
/* We dont want to talk to two processes at the
* same time */
if (Device_Open)
return -EBUSY;
/* If this was a process, we would have had to be
* more careful here, because one process might have
* checked Device_Open right before the other one
* tried to increment it. However, were in the
* kernel, so were protected against 页码：[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] 第4页、共19页 |
