Going from 2.2.12 to 2.2.17pre10

[Gabriel Paubert]

On Wed, 12 Jul 2000, Matt Porter wrote:

> > Residual data is useful for things like finding the memory size, and for
> > chips designed inside Apple. For almost everything else Linux already
> > contains a device tree, built by PCI probing when the kernel boots^*. I
> > don't see much need for a parallel, architecture specific, device tree.
>
> Whoa...you mentioned the key phrase here...it's really only useful or
> required for chips design inside Apple where you can't get documentation.
> "Residual data" and defined in the PReP spec is only found on PReP systems
> where all the hardware is fully documented so it's easy to size the
> memory by other means.  It's not that hard to read board registers or
> the memory controller setup.

Indeed, but there is one thing which is very hard to guess: interrupt
routing (due to the utterly stupid original Intel/IBM design which was
obsolete already before Neanderthal).

Actually very similar boards may have quite different interrupt routing
and break an unsuspecting kernel. I also hate all these tables with magic
values in the kernel (beside the fact that they don't work with
multifunction boards).

> I can see why the Mac folks have to deal with the broken OF device tree.
>
> A architecture specific (PPC) device tree (or residual data, if you will)
> would be part of a "standard" OpenSource firmware project.  It's only
> use would be to provide information for board bringup, etc.  It has it's
> advantages and disadvantages...

For ISA devices and interrupt routing, I consider it a big plus... For PCI
devices just ignore it if present.

	Gabriel.


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