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Re: acpivga(4) v. MI display controls

On Fri, Oct 15, 2010 at 08:29:57AM -0400, der Mouse wrote:
> ACPI may be the source of the information, but that doesn't mean it has
> to be how the autoconf tree is constructed.
> Compare and contrast with how NetBSD/sparc uses the OF (or is it OBP?
> I'm not sure) device tree to drive autoconf, but doesn't have a device
> node corresponding to OF that everything attaches under; it just uses
> the OF tree as the source of the data about what exists where.  (Well,
> much of it; autoconf doesn't totally mirror OF, eg, in SCSI device
> attachment.)

I do not know OF well, but my impression is that it is much, much less
invasive than what we have nowadays on x86 where close interaction between
the firmware and drivers are expected.

Several people seem to be under the false impression that this is something
only related to device attachment and autoconfiguration. It is not.

I tried to outline this in another mail, but frankly I think whether 'X
attachs to Y or Z' is just a little, largely irrelevant, detail in the face
of much bigger problems. In a nutshell: ACPI BIOS may access hardware directly,
with or without the consent from the system. In an entirely x86 based codebase
this is hardly a problem, but in NetBSD this comes down to the question on
how to maintain the clean MD/MI separation in the future.

- Jukka.

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