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Device driver overview

Driver as part of the kernel

Application programs, executing at the user level, are limited in the ways they can have an adverse impact upon the system. Performance and efficiency considerations are mostly confined to the program itself. An application program can consume excessive disk space, but it cannot raise its own priority level to use excessive amounts of processing time, nor does it have access to sensitive areas of the kernel or other processes.

Drivers can and do have much greater impact on the system. Inefficient driver code can severely degrade overall performance, and driver errors can corrupt or bring down the system. For this reason, testing and debugging driver code is particularly challenging, and must be done carefully. ``Driver testing and debugging'' discusses the facilities available for finding driver errors, as well as some of the special problems that are encountered when testing driver code.

Also, whereas an application program writer is free (within reasonable limits) to declare and use data structures and to use system services, a driver writer is constrained in several ways.


© 2005 The SCO Group, Inc. All rights reserved.
OpenServer 6 and UnixWare (SVR5) HDK - June 2005