Re: [PATCH] set altix preferred console

Mark Maule
2005-10-18T18:39:52Z

On Tue, Oct 18, 2005 at 12:33:06PM -0600, Bjorn Helgaas wrote:
> On Tuesday 18 October 2005 11:06 am, Luck, Tony wrote:
> > >> > I don't want to move pcdp.h under asm-ia64. EFI (and, I hope,
> > >> > PCDP) is coming to x86 soon. There's nothing ia64-specific
> > >> > in pcdp.h or pcdp.c, so I think it would be a mistake to
> > >> > move it to an arch-specific directory.
> > >>
> > >> Ok, thanks Bjorn. I was under the impression that stuff under dig64.org
> > >> was ia64 specific ...
> > >>
> > >> Would moving it to include/linux be an option?
> > >
> > >I sort of hate to put it in include/linux, too, but I guess
> > >it's already a dumping ground for all sorts of miscellaneous
> > >stuff, so one more wouldn't make it much worse.
> > >
> > >And I can't think of any better options.
> >
> > The comments at the head of pcdp.h certainly make it look
> > very ia64 specific. Are there any newer EFI documents that
> > it could point to instead of the dig64.org URLs?
>
> The point of the PCDP is to tell the OS what console firmware
> was using, so you don't need "console=" arguments. It's
> defined to be very easy to parse, so the OS can use it before
> ACPI or PCI device enumeration.
>
> So other than the URL that contains "dig64", there's nothing
> ia64-specific. Matt Tolentino (Intel) was hoping that the
> PCDP or something similar would eventually be supported on
> x86 as well. But that world still has its blinders on and
> assumes all the world is VGA, and seems to think that if you
> want something other than VGA, by George, you ought to *have*
> to use "console=".
>
> > Linus is just as fond of EFI as he is of ACPI (i.e. not at all),
> > so I don't think he'll be too happy with include/linux/pcdp.h
> > If it really is the only place for this to move, then this discussion
> > needs to happen on linux-kernel, not on linux-ia64.
> >
> > Since PCDP is closely linked to ACPI, would include/acpi/pcdp.h
> > be at all plausible?
>
> PCDP is not linked with ACPI at all, except that it happens to
> use an address structure that matches the ACPI "generic address".
> We should probably just duplicate that structure definition and
> kill the linux/acpi.h include.
>
> > Or, merge the contents into include/linux/efi.h?
>
> This would be a possibility. But other than the fact that we
> get the address of the PCDP from EFI, there's no EFI dependency
> either.
>
> The only problem with the current location is that SGI firmware
> doesn't have quite enough device enumeration support for their
> VGA devices, so they have to depend on the PCDP as a crutch. So
> maybe we should just leave pcdp.h alone and make SGI duplicate
> what they need.

I'm ok with that too. Just thought it was a little neater to not dup the
structs. This is probably better in the long run anyway as we can more
easily rip the crutches out as we move forward with ACPI.

Mark