Device Driver Interfaces Intro(9)
NAME
Intro, intro - introduction to device driver interfaces
DESCRIPTION
Section 9 provides reference information needed to write
device drivers for Solaris 2.x. It describes the interfaces
provided by the Device Driver Interface Driver-Kernel Inter-
face (DDI/DKI). Drivers that conform to this specification
are more likely to work in future releases and may be port-
able to other environments.
Porting
Software is usually considered portable if it can be adapted
to run in a different environment more cheaply than it can
be rewritten. The new environment may include a different
processor, operating system, and even the language in which
the program is written, if a language translator is avail-
able. Likewise the new environment might include multiple
processors. More often, however, software is ported between
environments that share an operating system, processor, and
source language. The source code is modified to accommodate
the differences in compilers or processors or releases of
the operating system.
In the past, device drivers did not port easily for one or
more of the following reasons:
o To enhance functionality, members had been added to ker-
nel data structures accessed by drivers, or the sizes of
existing members had been redefined.
o The calling or return syntax of kernel functions had
changed.
o Driver developers did not use existing kernel functions
where available, or relied on undocumented side effects
that were not maintained in the next release.
o Architecture-specific code had been scattered throughout
the driver when it could have been isolated.
Operating systems are periodically reissued to customers as
a way to improve performance, fix bugs, and add new
features. This is probably the most common threat to compa-
tibility encountered by developers responsible for maintain-
ing software. Another common problem is upgrading hardware.
As new hardware is developed, customers occasionally decide
to upgrade to faster, more capable computers of the same
family. Although they may run the same operating system as
those being replaced, architecture-specific code may prevent
the software from porting.
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Device Driver Interfaces Intro(9)
Scope of Interfaces
Although application programs have all of the porting prob-
lems mentioned, developers attempting to port device drivers
have special challenges. Before describing the DDI/DKI, it
is necessary to understand the position of device drivers in
operating systems.
Device drivers are kernel modules that control data
transferred to and received from peripheral devices but are
developed independently from the rest of the kernel. If the
goal of achieving complete freedom in modifying the kernel
is to be reconciled with the goal of binary compatibility
with existing drivers, the interaction between drivers and
the kernel must be rigorously regulated. This driver/kernel
service interface is the most important of the three distin-
guishable interfaces for a driver, summarized as follows:
o Driver-Kernel. I/O System calls result in calls to
driver entry point routines. These make up the kernel-
to-driver part of the service interface, described in
Section 9E. Drivers may call any of the functions
described in Section 9F. These are the driver-to-kernel
part of the interface.
o Driver-Hardware. All drivers (except software drivers)
must include code for interrupt handling, and may also
perform direct memory access (DMA). These and other
hardware-specific interactions make up the
driver/hardware interface.
o Driver-Boot/Configuration Software. The interaction
between the driver and the boot and configuration
software is the third interface affecting drivers.
Scope of the DDI/DKI
The primary goal of the DDI/DKI is to facilitate both source
and binary portability across successive releases of the
operating systems on a particular machine. In addition, it
promotes source portability across implementations of UNIX
on different machines, and applies only to implementations
based on System V Release 4. The DDI/DKI consists of
several sections:
o DDI/DKI Architecture Independent - These interfaces are
supported on all implementations of System V Release 4,
and will be supported in future releases of System V.
o DKI-only - These interfaces are part of System V Release
4, and may not be supported in future releases of System
V. There are only two interfaces in this class,
segmap(9E) and hat_getkpfnum(9F).
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Device Driver Interfaces Intro(9)
o Solaris DDI - These interfaces specific to Solaris, and
will be supported in future releases of Solaris 2.x.
o Solaris SPARC specific DDI - These interfaces are
specific to the SPARC processor, and may not be available
on other processors supported by Solaris.
o Solaris x86 specific DDI - These interfaces are specific
to the x86 processor, and may not be available on other
processors supported by Solaris.
To achieve the goal of source and binary compatibility, the
functions, routines, and structures specified in the DDI/DKI
must be used according to these rules.
o Drivers cannot access system state structures (for exam-
ple, u and sysinfo) directly.
o For structures external to the driver that may be
accessed directly, only the utility functions provided in
Section 9F should be used. More generally, these func-
tions should be used wherever possible.
o The headers <sys/ddi.h> and <sys/sunddi.h> must be the
last header files included by the driver.
Audience
Section 9 is for software engineers responsible for creat-
ing, modifying, or maintaining drivers that run on this
operating system and beyond. It assumes that the reader is
familiar with system internals and the C Programming
Language.
How to Use Section 9
Section 9 is divided into three subsections:
9E Driver Entry Points - contains reference pages for all
driver entry point routines.
9F Kernel Functions - contains reference pages for all
driver support routines.
9S Data Structures - contains reference pages for driver-
related structures.
SEE ALSO
intro(9E), intro(9F), intro(9S)
NOTES
SunSoft's implementation of the DDI/DKI was designed to pro-
vide binary compatibility for third-party device drivers
across currently supported hardware platforms across minor
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Device Driver Interfaces Intro(9)
releases of the operating system.
However, unforeseen technical issues may force changes to
the binary interface of the DDI/DKI. We cannot therefore
promise or in any way assure that DDI/DKI-compliant device
drivers will continue to operate correctly on future
releases.
Furthermore, future releases may contain additions to the
DDI/DKI to support future platforms. At that time device
drivers wishing to operate across the new set of supported
platforms may require these additions.
SunOS 5.8 Last change: 28 Jan 1994 4
© 1994 Man-cgi 1.15S, Panagiotis Christias <christia@theseas.ntua.gr>
1995 Modified for Solaris 2.3, David Adams, <d.j.adams@soton.ac.uk>
Solaris Man Pages