[coreboot] coreboot specific ACPI table

[ron minnich]

Wait, I thought it had to be 4 characters.

ron

On Fri, Apr 22, 2016 at 2:36 PM Aaron Durbin via coreboot <
coreboot at coreboot.org> wrote:

> On Fri, Apr 22, 2016 at 2:00 PM, Duncan Laurie <dlaurie at chromium.org>
> wrote:
> > On Tue, Apr 19, 2016 at 6:49 AM, Aaron Durbin <adurbin at google.com>
> wrote:
> >>
> >> On Mon, Apr 18, 2016 at 10:17 PM, Julius Werner <jwerner at chromium.org>
> >> wrote:
> >> > I think we should only export the coreboot table location and size
> >> > through ACPI and then read everything else from there. That way we can
> >> > share almost all of the kernel driver code with ARM and just need a
> >> > tiny platform-specific stub to look up the table location first. If we
> >> > add all the information into an actual ACPI table, we're building an
> >> > x86-only solution again. (A generic, platform-independent coreboot
> >> > driver could just as easily export the stuff we want into sysfs.)
> >> >
> >>
> >> That's fine. The only thing I was concerned about was implementing an
> >> ACPI table proper or try to do some ACPI device shenanigans like the
> >> ramoops device. coreboot doesn't currently have a ACPI ID assigned to
> >> it. If we go with a ACPI device coreboot should apply for an ACPI ID.
> >> I personally think the coreboot ACPI table seems more straight
> >> forward, but I was wondering if people knew of any downsides to going
> >> that route.
> >>
> >
> >
> > The official tables are all defined in the ACPI spec while the related
> > tables are also linked to from the spec, so we'd need to convince the
> UEFI
> > forum to at least reserve the signature for us (and then link to our
> table
> > definition) since they intend to act as gatekeepers to avoid collisions
> in
> > table signatures:
> >
> > "Requests to reserve a 4-byte alphanumeric table signature should be
> sent to
> > the email address info at acpi.info and should include the purpose of the
> table
> > and reference URL to a document that describes the table format."
> >
> > An easier path would be to define a specific device in the DSDT and
> populate
> > it with the various data we want to be there on every system.  That would
> > allow us to control the format and be able to alter it in the future if
> we
> > want to expose new information.
> >
> > As you note a Device would need a valid unique HID, and that needs an ID
> > prefix if it wants to be official.  In theory we could request something
> > like "CORE" as an official APCI ID from
> > http://www.uefi.org/PNP_ACPI_Registry
>
> OK. Time for bikeshedding:
>
> 1. CORE
> 2. CBOOT
> 3. ... ?
>
> Stefan, we'll likely need you to request the HID w/ your coreboot.org
> email.
>
> >
> > I suppose the real difference between the two is whether we need this
> data
> > early in boot before there is an AML interpreter available in the OS.
>
> I don't think we need it that early. Right now the current usage (at
> least on x86) is all very late since we're doing AML evaluation. We
> could go w/ the ACPI device first. Just need to request that HID.
>
> >
> > -duncan
> >
> >
> > --
> > coreboot mailing list: coreboot at coreboot.org
> > https://www.coreboot.org/mailman/listinfo/coreboot
>
> --
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>
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