Interrupt routing in prep_pci.c

Johnnie Peters jpeters at
Mon Feb 22 03:56:43 EST 1999

Hi Gabriel

I would like to try your stuff out but I have not been able to get to your site.  Do
you have it anywhere else I can retrieve it from?

I tried a version of it a while back and it did not seem to compile with the standard
R4 compiler.  At that time I tried to compile and use the latest egcs and binutils
stuff and it seemed to work for the kernel but when I tried compiling user level
stuff it gave me several problems.  I have asked several people on the net and have
not got a good answer as to what compiler I should be using with R4.  Can you tell me
the combination you are using?

Thanks for your time,


Gabriel Paubert wrote:

> On Wed, 10 Feb 1999, Jeremy Fitzhardinge wrote:
> >
> > Hi Cort/all,
> >
> > I'm trying to work out what kernel/prep_pci.c is doing with interrupt routing.
> > I'm looking at the stuff in the standard 2.2 kernel, so perhaps there's a better
> > place for me to look.
> >
> > Firstly, in route_pci_interrupts it does an inb(0x800) to get something to
> > determine the interrupt architecture of the board.  What is this value, and
> > where does it come from?
> It's a value which give sthe board type on rather old IBM/Motorola boards.
> > Rather than having hard-coded tables, can't the interrupt routing be determined
> > from either firmware or the interrupt controller itself?  The comment at the
> > top of the file is that this will go away soon.  What are you planning to
> > replace it?
> Indeed, that's what I do from residual data on PreP machines and it seems
> to work on several kinds of boards. You'll find it embedded somewhere
> in the patch file at:
> > Background: I'm porting LinuxPPC to a Yellowknife-like board running Open
> > Firmware.  It works well except that the drivers can't find their interrupts.
> Note that this patch includes a new bootloader for PreP machines, I'd like
> to extend it to support OF too but don't have te time right now.
>         Gabriel.

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