In System V Release 4 (SVR4), the interface between device drivers and the rest of the UNIX kernel was standardized as the DDI/DKI. The DDI/DKI is documented in section 9 of the Reference Manual Collection. Section 9E documents driver entry points, section 9F documents driver-callable functions, and section 9S documents kernel data structures used by device drivers. See Intro(9E), Intro(9F), and Intro(9S).
The DDI/DKI is intended to standardize and document all interfaces between device drivers and the rest of the kernel. In addition, the DDI/DKI enables source and binary compatibility for drivers on any machine that runs the Solaris OS, regardless of the processor architecture, whether SPARC or x86. Drivers that use only kernel facilities that are part of the DDI/DKI are known as DDI/DKI-compliant device drivers.
The DDI/DKI enables you to write platform-independent device drivers for any machine that runs the Solaris OS. These binary-compatible drivers enable you to more easily integrate third-party hardware and software into any machine that runs the Solaris OS. The DDI/DKI is architecture independent, which enables the same driver to work across a diverse set of machine architectures.
Platform independence is accomplished by the design of DDI in the following areas:
Dynamic loading and unloading of modules
Accessing the device space from the kernel or a user process, that is, register mapping and memory mapping
Accessing kernel or user process space from the device using DMA services
Managing device properties