Subject: Re: Hypothetical Question...
From: Benjamin Herrenschmidt (bh40@calva.net)
Date: Wed Dec 06 2000 - 16:31:29 MST
>The NDRV? That is an ordinary MacOS driver and MacOS X should not
>be able to use it. (Or, is there a compatibility mode I haven't
>heard about? With some glue code, I imagine it would be possible
>to get an old MacOS video driver binary working in MacOS X.)
Yes, MacOS X can use some of the "ndrv"'s out there, especially the
ROM based video ones.
The original "ndrv" API design was supposed to provide compatibility
with Copland (the dead MacOS 8) and so was designed to avoid as much
as possible legacy MacOS functions.
An ndrv is supposed to link only against some specific libs (like
DriverServices or VideoServices).
In real life, only some video drivers completely followed these guidelines.
MacOS X contains a small compatibility layer in the kernel that can
"wrap" some ndrvs. It provides some CFM loading capabilities, an a re-
implementation of
some of those libraries. It's only used for video, and only for
initialization and mode switching.
It's all (or almost all) in the xnu (Apple's kernel) source code.
Ben.
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