SDI pass-through interface
The SDI pass-through interface
gives a user program direct access to a device.
By permitting user programs to act in a
manner similar to a target driver,
the overhead of instructions needed
to make device-specific requests
can be removed from a target driver.
An example of device-specific requests
are the instructions required to format a disk.
With the pass-through interface,
a user program can select different instruction packages
for different vendors' drives.
Not only can many instructions be
removed from a driver, but a driver can be made
to work on a wider range of different devices.
In addition, a driver need not be updated as frequently when
a device changes.
The pass-through interface gives you a means
of evaluating new peripherals and
controllers without developing a driver, checking device states, and
eliminates duplication of driver code.
Two pass-through interface schemes are available:
pass-through library interface
The pass-through library interface,
implemented through the /dev/passthru0 device
and the (libsdi.so) library,
provides routines that applications can use
to issue device-specific requests.
It supports extended SCSI addressing
and is not available on systems prior to UnixWare 7 Release 7.1.
``Using the pass-through library interface''.
pass-through ioctl interface
Uses pre-defined ioctl requests to issue device-specific requests.
This was the only pass-through interface on pre-Release 7.1 systems,
and is supported for compatibility with earlier systems and existing drivers.
Applications written for Release 7.1 should use the pass-through library interface.
The ioctl interface does not
support extended SCSI addressing.
``Using the pass-through ioctl interface''.
© 2005 The SCO Group, Inc. All rights reserved.
OpenServer 6 and UnixWare (SVR5) HDK - June 2005