BSP Developer's Guide

F
Generic Drivers
F.1 Introduction
This appendix provides guidelines for writing generic drivers for the handful of
devices that are common to most BSPs. Although BSPs can differ considerably in
detail, there are some needs that are common to almost all. For example, most BSPs
require a serial device driver or a timer driver. Ideally, the drivers for these devices
would be generic enough to port to a new BSP with a simple recompilation. This
reuse of code reduces your maintenance overhead and lets you focus your testing
efforts, which results in better tested code. For example, using generic drivers let
Wind River save 500 lines of C source code in three similar BSPs. 1
To help you use generic drivers across multiple similar BSPs, the BSP kit includes
source for generic drivers in the target/src/drv directory. At compile time, sysLib.c
(a file duplicated in every BSP) can include generic drivers from the target/src/drv
directory as needed. As you develop drivers for your BSPs, you should strive to
create drivers that are generic enough to service multiple BSPs. You can add such
drivers to those in the target/src/drv directory.
However, when dealing with atypical hardware or legacy code, it might not be
practical to use a generic driver. Some hardware designs are just too different to
work with a generic driver. In the case of legacy code, it might be possible to use a
generic driver. Unfortunately, reworking the BSP to use a generic driver might not
be worth the effort, especially if you are just upgrading the BSP to a new release of
VxWorks. In either case, you must create or maintain a BSP-specific driver. Such a
1. VxWorks network and SCSI device drivers (distributed in object form) are not discussed
here, but are covered in other appendices in this manual.
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