Platform numbers

Michael Ellerman michael at
Sat Jul 9 15:00:09 EST 2005

On Sat, 9 Jul 2005 13:45, Benjamin Herrenschmidt wrote:
> On Fri, 2005-07-08 at 11:52 -0500, Olof Johansson wrote:
> > On Fri, Jul 08, 2005 at 10:45:06PM +1000, Michael Ellerman wrote:
> > > Hi y'all,
> > >
> > > Are the platform numbers in asm-ppc64/processor.h private to Linux? Or
> > > do firmware/hardware know about them?
> > >
> > > For pseries/pmac/maple it looks like we just assign them based on OF
> > > properties. For iSeries we check in the naca. I don't see where BPA
> > > gets assigned?
> > >
> > > The reason I ask is PLATFORM_MAPLE is currently 0x0500 which means we
> > > can't (easily) do any bit mask based trickery on platform numbers.
> >
> > They are just local to Linux and you can change them if you see a need
> > to. Only thing to think about is the LPAR bit (0x1).
> No, they are not local. Think about kexec, and firmwares that directly
> pass a flattened device-tree

Ok. But AIUI there isn't any firmware yet which does that? So we could change 
the MAPLE number now and get away with it?

> > Only challenge with going with bitmap is that the number of possible
> > platforms are quite a bit lower, I'm not sure how quickly that will hurt
> > us. We'll have other, bigger, headaches before we run out of platform
> > bits anyway.
> Yes, but I think we should kill the platform number. We should replace
> it with a "HV type" (native, iseries, rpa, xen, ...) and have the
> ppc_md.probe() function use the device-tree to identify the platform.
> There are bits & pieces here or there that will need to be fixed for
> that approach to work though. Like gross hacks in the interrupt tree
> parsing.

We'd still have the problem that there's little bits of code outside of ppc_md 
functions which uses the platform number to work out which platform it's on. 
How would it check what platform it was on without the number?

I also see we #define _machine (systemcfg->platform) for drivers?


Michael Ellerman
IBM OzLabs

phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person
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