Subject: Re: Kernel questions

From: "David N. Welton" <[email-masked]>
Date: Mon, 18 Oct 1999 12:13:53 -0700

On Mon, Oct 18, 1999 at 08:53:34PM +0200, Benjamin Herrenschmidt wrote:
> 
> On Mon, Oct 18, 1999, David N. Welton <[email-masked]> wrote:

> >1) Why does everything seem to want to access NVRAM things?  I've
> >   found it scattered in several places throughout the kernel, such as
> >   matroxfb.c.
 
> Mostly to find out the video mode last set by MacOS. It doesn't
> always works since new MacOS versions may no longer put the mode
> where it used to be. It's also used by the PMU code on some
> PowerBooks to read the current backlight setting.

Well, supposing one doesn't have a Macintosh or MacOS, then this stuff
is basically useless, no?  At least for how it's being used currently.

> >3) Why does pmac_support.c assume that you have ADB stuff compiled in?
> 
> All pmacs have an ADB controller, even if it's not visible (they have at
> least the controller). Some pmac-specific calls go thru /dev/adb even
> when you don't have anything on the ADB bus for historical reasons, like
> userland access to the real time clock (ioctls). The new UMA machines
> still have various ADB calls implemented in the PMU (and used by the iBook).

Once again, I don't have a pmac...

> >nvram_read_byte contains: "struct adb_request req".
> >
> >If I have understood correctly, ADB is an Apple thing, and really
> >shouldn't have anything to do with my RS6000.  Is this correct?
 
> Yes, it's correct. However, I beleive the kernel is compiled to boot
> on CHRP _and_ PowerMacs, and so the ADB support is needed. Also, the
> CHRP definition states that CHRP machines can have an ADB controller
> too.

There are a few options:

PowerMac
Prep/MTX
CHRP
PowerMac/PReP/CHRP
Gemini
APUS

I'm compiling as CHRP, and since ADB is selectable as an option, it
seems it could be added in anyway, pmac or not?

So would it be a worthwhile endeavour to try and ifdef this stuff out,
for those of us who don't need it?

Thanks,
-- 
David N. Welton, Developer, Linuxcare, Inc.
415.354.4878 x241 tel, 415.701.7457 fax
[email-masked], http://www.linuxcare.com/
Linuxcare. At the center of Linux.

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