Moving on into the driver code proper, the first thing to look at is the initialization function, tdd_init():

	void tdd_init(void)
	{
		tdd_trace = TRUE;

		if (register_chrdev(3O, "tdd", &tdd_fops)) 
			TRACE_TXT("Cannot register tdd driver as major device 30")
		else
		TRACE_TXT("Tiny device driver registered successfully")

		qhead = 0; 
		write_busy = FALSE; 
		read_busy = FALSE; 
		tdd_trace = FALSE; 
		return;
	}

This routine is executed at system boot time. Remember that a call to the routine needs to be added to the chr_dev_init() function in the file:

	/usr/src/linux/drivers/char/mem.c

assuming your kernel source is stored in /usr/src/linux.

When tdd_init() is executed it calls the kernel function register_chrdev() to add its file_operations structure to the character device routine address table. A message is displayed on the machine console, using the debug trace facility, to report the success or failure of this operation. The routine then initializes the driver's static variables and finally returns.

Next: open Function

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