Kernel questions

Kernel questions

[David N. Welton]

Hi, I have several questions regarding the latest devel kernel
(2.3.22), that I am trying to get running on an RS6000.

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.

2) Why is it trying to compile and use pmac_support (amongst other
   pmac_* things).  I have it set to the CHRP architecture.

3) Why does pmac_support.c assume that you have ADB stuff compiled in?

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?

I'm sorry if some of these are silly questions, and hope my ignorance
isn't too glaring:-)

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

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Re: Kernel questions

[Benjamin Herrenschmidt]

On Mon, Oct 18, 1999, David N. Welton <davidw@linuxcare.com> 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.

>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).

>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.

>I'm sorry if some of these are silly questions, and hope my ignorance
>isn't too glaring:-)


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Re: Kernel questions

[David N. Welton]

On Mon, Oct 18, 1999 at 08:53:34PM +0200, Benjamin Herrenschmidt wrote:
> 
> On Mon, Oct 18, 1999, David N. Welton <davidw@linuxcare.com> 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
dwelton@linuxcare.com, http://www.linuxcare.com/
Linuxcare. At the center of Linux.

** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/

Re: Kernel questions

[Geert Uytterhoeven]

On Mon, 18 Oct 1999, David N. Welton wrote:
> > 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?

Isn't that already done in the latest 2.3.x?

Greetings,
--
Geert Uytterhoeven -- Linux/{m68k~Amiga,PPC~CHRP} -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds


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Re: Kernel questions

[David N. Welton]

On Tue, Oct 19, 1999 at 06:36:49PM +0200, Geert Uytterhoeven wrote:

> > > 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.

> > 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?

> Isn't that already done in the latest 2.3.x?

I'm working with 2.3.22, and it hasn't been done, afaict.

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

** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/

Re: Kernel questions

[Gabriel Paubert]

On Mon, 18 Oct 1999, David N. Welton wrote:

> There are a few options:
> 
> PowerMac
> Prep/MTX
> CHRP
> PowerMac/PReP/CHRP
> Gemini
> APUS

Actually I had the impression that the first three should disappear and
you should use the common PMAC/PreP/CHRP for these machines. I'm using
MVME boards (closer to MTX) with this option and a few patches since it
boots in PreP moe and I remap it to CHRP for VME addressing capability
reasons.


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

I don't think that I have ADB compiled in (I'll check again). The only
problem is that I'm looking for a clock program which assumes that you are
on a PowerMac.

	Regards,
	Gabriel.


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