RTEMS 4.9.2 On-Line Library

I/O Manager Device Driver Interface

RTEMS Ada User's Guide

16.2.6: Device Driver Interface

When an application invokes an I/O manager directive, RTEMS determines which device driver entry point must be invoked. The information passed by the application to RTEMS is then passed to the correct device driver entry point. RTEMS will invoke each device driver entry point assuming it is compatible with the following prototype:

function IO_Entry (
  Major          : in     RTEMS.Device_Major_Number;
  Minor          : in     RTEMS.Device_Major_Number;
  Argument_Block : in     RTEMS.Address
) return RTEMS.Status_Code;

The format and contents of the parameter block are device driver and entry point dependent.

It is recommended that a device driver avoid generating error codes which conflict with those used by application components. A common technique used to generate driver specific error codes is to make the most significant part of the status indicate a driver specific code.

RTEMS Ada User's Guide