open() and release()

• int foo_open (struct inode *i, struct file *f)

• Called when user-space opens the device file.
• inode is a structure that uniquely represent a file in the system (be it a regular file, a directory, a symbolic link, a character or block device)
• file is a structure created every time a file is opened. Several file structures can point to the same inode structure.
• Contains informations like the current position, the opening mode, etc.
• Has a void *private_data pointer that one can freely use.
• A pointer to the file structure is passed to all other operations

• int foo_release(struct inode *i, struct file *f)

• Called when user-space closes the file.