Solaris Transition Guide

Device Driver Interfaces

In previous SunOS releases, a driver writer had to cope with changes in the device driver interfaces. Usually, there was a porting effort with each release of the operating system. In addition, the interfaces for each platform varied, so device drivers often required separate releases for each platform. Third-party device driver releases often included complex scripts that would reconfigure and rebuild the operating system in order to integrate a device driver. It was costly to support and maintain device drivers.

Unlike previous releases of SunOS systems (SunOS release 4.1.3 software and earlier), the device driver interfaces in the Solaris 7 operating environment are formalized and are referred to as the Solaris 7 SPARC DDI/DKI. The Solaris 7 SPARC DDI/DKI provides binary compatibility of device drivers across all supported platforms and for all future releases of the Solaris 7 operating environment on those platforms.

The term DDI/DKI is derived from the original specification as supplied in the SVR4 release. It stands for device driver interface/driver kernel interface. The interfaces are divided into three groups:


The DDI/DKI interfaces were standardized in SVR4, and are generic across all implementations of SVR4, regardless of the platform on which they are running.


The DKI-only interfaces are generic like the DDI/DKI interfaces and are supported in all SVR4 implementations. However, they are not guaranteed to be supported in future releases of System V.


The DDI-only interfaces are intended to be architecture-specific; for example, methods to access and control-device and system-specific hardware (that is, I/O registers, DMA services, interrupts, and memory mapping). These interfaces are not guaranteed to work in other SVR4 implementations.

This group of features effectively lowers the cost of driver support and maintenance. These features, combined with the large number of SPARC platforms, are helpful to many new third-party hardware developers.

With this level of binary compatibility, third-party hardware developers can now "shrink-wrap" their DDI-compliant device drivers with their driver hardware. Installing a new driver package can now be entirely automated. The self-configuring kernel removes the necessity for recompiling the kernel to add or remove a driver. Thus, a DDI-compliant device driver for Solaris 7 environments can be treated like any other consumer software product.

In the Solaris 7, DDI/DKI the DDI-only interfaces are generic to all systems that support the Solaris 7 DDI/DKI. Note that the interfaces that make up the common SCSI architecture (SCSA), and the locking interfaces used to make the driver behave correctly in a multithreaded kernel, are also considered DDI-only interfaces in the Solaris 7 operating environment.

SCSA shields device drivers from details specific to the platform relating to host adapter implementations. With SCSA, a SCSI driver can run on all supported platforms.

A device driver that restricts itself to using only interfaces in the categories desribed above is said to be Solaris 7 DDI/DKI compliant. A Solaris 7 DDI/DKI compliant device driver is commonly referred to as a DDI-compliant device driver.


The man pages for the driver routines, structures, and support routines that comprise the DDI/DKI can be found in the sections of man Pages(1M): System Administration Commands listed below. See the Intro(9) man page for more information about these sections.

A Device Driver Developers Kit (DDK) is available separately.