SCO UNIX *double* device driver

[Guy Harris]

>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.