[coreboot] coreboot specific ACPI table

[Aaron Durbin]

On Fri, Apr 22, 2016 at 2:38 PM, ron minnich <rminnich at gmail.com> wrote:
> Wait, I thought it had to be 4 characters.

Yes. I cannot count. :/ CRBT
>
> 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
>> >
>> >
>> > --
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>>
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