The release function, tdd_release(),is called when the last process that is holding open each of the device special files associated with this device driver closes it with a close() call. In fact, since only one process at a time can open each of the device special files for this driver, then a close() from this process will also call the driver release routine (tdd_release()):

	static void tdd_release(struct mode *inode, struct file *file)
	{
		TRACE_TXT("tdd_release")

		switch (MIN0R(inode->i_rdev))
		{
			case TDD_WRITE:
				write_busy = FALSE; 
				return;
			case TDD_READ:
				read_busy = FALSE; 
				return;
		}
	}

All that tdd_release() does is to reset the appropriate read or write busy flag, ready for the next open() operation to take place on the device special file.

Next: write Function

---