Minor Nodes and Minor Numbers

Drivers are responsible for managing their minor number name space. For example, the sd driver needs to export 16 minor nodes (8 character, 8 block) to the file system for each disk. Each represents a different piece of the same disk, or a different interface to the same data (character/block). However, the driver still needs to be able to retrieve the instance number of the device in order to get soft state, and so forth. The getinfo(9E) entry point informs the system about the mapping from minor number to device instance (see The getinfo() Entry Point).