linux-kernel - Re: [RFC/PATCH 2.6.32] Simple Firmware Interface (SFI): initial support

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Date:	Tue, 23 Jun 2009 17:33:59 -0400 (EDT)
From:	Len Brown <lenb@...nel.org>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	sfi-devel@...plefirmware.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC/PATCH 2.6.32] Simple Firmware Interface (SFI): initial support

On Tue, 23 Jun 2009, Matthew Garrett wrote:

> On Tue, Jun 23, 2009 at 04:00:55PM -0400, Len Brown wrote:
> 
> > But given that the hardware is fixed (it was fixed over a year ago),
> > the question becomes what does ACPI mean on such a platform?
> > It turns out that if you look at the ACPI spec and delete all the
> > things that could not possibly apply to MRST, then you are left
> > with very little.
> 
> Right, but instead you've effectively taken ACPI, done s/XSDT/SYST/ and 
> then only supported a subset of the static tables and added some others.

sfi_acpi_table_parse(ACPI_SIG_MCFG, NULL, NULL, 0, pci_parse_mcfg);

is used today to provide access to a standard PCI-SIG-defined ACPI-wrapped
static MMCONFIG table via a standard ACPI XSDT.

No, this doesn't mean that the platform firmware supports ACPI mode.
The XSDT simply keeps the SFI table name space from conflicting
with the ACPI table name-space.

If there is a need to access another ACPI defined/reserved signature
table, the same mechanism can be used -- just fill in the signature
and the routine to parse the table.

> In return we gain two implementations to debug. I'm absolutely fine with 
> the concept of a cut-down ACPI, but I'm pretty uncomfortable with it 
> being implemented as a single-vendor spec.  Right now SFI's a 
> reimplementation of functionality we already have for the benefit of a 
> single chipset, whereas instead it could have been a refactoring of the 
> ACPI codebase to allow vendors to include whatever subset of the ACPI 
> functionality they felt necessary.

It is a fact that the list of things that SFI could have been,
and the list of things that SFI is not,
are _both_ much larger than the list of things it is.

cheers,
-Len Brown, Intel Open Source Technology Center

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