[RFC] powerpc: Document new property called interrupt-parents

[Yoder Stuart-B08248]

> -----Original Message-----
> From: David Gibson [mailto:david at gibson.dropbear.id.au] 
> Sent: Tuesday, February 27, 2007 6:56 PM
> To: Yoder Stuart-B08248
> Cc: paulus at samba.org; linuxppc-dev at ozlabs.org
> Subject: Re: [RFC] powerpc: Document new property called 
> interrupt-parents
> 
> On Tue, Feb 27, 2007 at 04:54:45PM -0600, Stuart Yoder wrote:
> > 
> > Document new property called interrupt-parents which can
> > be used to represent interrupts for devices that route
> > interrupts to more than one interrupt controller.
> 
> Well, whatever Segher says, I'm still very concerned about the
> potential for extra difficulty in debugging with this approach.

The issue, as I understand it, is the potential for an old
kernel parser to silently misparse a new dev tree with this
new property.

Do the version and last_comp_version in the blob header
help here?

If new dev trees with this new property were encoded with a
version=0x17 and last_comp_version=0x17 would the old
kernel parser error out if it only supported up to 0x16?

I'm not sure or not if that is the intended use of those
fields, but I think parser/DTS compatibility issues could
be solved by some kind of versioning.

It's more of a general problem.

Stuart