it may have as many structures $<device>_info$ as there are minor devices
active. $Register_cdrom()$ builds a linked list from these.
-\subsection{$Int\ unregister_cdrom(struct\ cdrom_device_info * cdi)$}
+\subsection{$Void\ unregister_cdrom(struct\ cdrom_device_info * cdi)$}
Unregistering device $cdi$ with minor number $MINOR(cdi\to dev)$ removes
the minor device from the list. If it was the last registered minor for