RTEMS 4.6.1 On-Line Library

Analog Driver Major and Minor Numbers

BSP and Device Driver Development Guide

17.1: Major and Minor Numbers

The major number of a device driver is its index in the RTEMS Device Address Table.

A minor number is associated with each device instance managed by a particular device driver. An RTEMS minor number is an unsigned32 entity. Convention calls dividing the bits in the minor number down into categories like the following:

board - indicates the board a particular device is located on
port - indicates the particular device on a board.

From the above, it should be clear that a single device driver can support multiple copies of the same board in a single system. The minor number is used to distinguish the devices.

BSP and Device Driver Development Guide