Xref: utzoo comp.unix.internals:2412 comp.unix.sysv386:6255
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!cs.utexas.edu!uunet!auspex!guy
From: guy@auspex.auspex.com (Guy Harris)
Newsgroups: comp.unix.internals,comp.unix.sysv386
Subject: Re: SCO UNIX *double* device driver
Message-ID: <6806@auspex.auspex.com>
Date: 23 Mar 91 21:22:02 GMT
References: <905@zeusa.UUCP>
Followup-To: comp.unix.internals
Organization: Auspex Systems, Santa Clara
Lines: 14

>At first this seemed like a perfect application for STREAMS,

Given that disk drivers rarely, if ever, use STREAMS (there's no way to
do an "lseek()" on a stream, and have it do something meaningful, for
example, unless your system has been rewhacked to send some funny
message downstream on a seek), it seems like a perfectly lousy
application for STREAMS....

The right way to do this is probably to have a pseudo-disk driver that
has the standard block-device and character-device interfaces that a
real disk driver does, that also has special "ioctl"s to tell it which
pseudo-disk devices talk to which real disk devices, and that ends up
directly calling the device driver entries of the real disk driver or
drivers.