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.