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    SubjectRe: [PATCH v3] dcdbas: Add support for WSMT ACPI table
    On Fri, Jun 29, 2018 at 9:56 PM, Stuart Hayes <stuart.w.hayes@gmail.com> wrote:
    > On 06/27/2018 06:52 PM, Andy Shevchenko wrote:
    >> On Fri, Jun 15, 2018 at 1:31 AM, Stuart Hayes <stuart.w.hayes@gmail.com> wrote:
    >>> On 6/14/2018 12:25 PM, Andy Shevchenko wrote:
    >>>> On Thu, Jun 14, 2018 at 5:22 PM, Stuart Hayes <stuart.w.hayes@gmail.com> wrote:
    >>>>> On 6/13/2018 3:54 AM, Andy Shevchenko wrote:

    >>>> Thanks, but here I meant += 1 vs += 16 step.

    > I did realize that the debug code that printed the address of the EPS table was not
    > working right, and the table on my system is actually 16-byte aligned. However,
    > the documentation on the EPS does not specify that it will be 16-byte aligned, so I
    > don't think the driver should make that assumption, especially since scanning a 64K
    > region byte by byte should take very little extra time over scanning every 16th byte.

    > I guess this isn't needed since the table on my system actually is 16-byte aligned.

    I think the 16 byte is a natural alignment applicable to all tables like a such.
    I would rather go with it until we will get a (weird) BIOS which does
    not support that.

    (I believe this alignment just comes by definition of C ABIs for the
    structures / types. So, each defined type is located on an aligned
    boundaries)

    >>> [ 4680.194012] dcdbas dcdbas: WSMT found, using firmware-provided SMI buffer.
    >>> [ 4680.195327] dcdbas dcdbas: Dell Systems Management Base Driver (version 5.6.0-3.3)
    >>
    >> OK, now the most important question, did you investigate "SMM
    >> Communication ACPI Table"?
    >> Can you utilize information in it?

    > Dell BIOS does not provide a "SMM Communication ACPI Table", just the EPS. It appears
    > that the "SMM Communication ACPI Table" is deprecated in the UEFI 2.7 spec. Also, the
    > dcdbas driver is for Dell systems only.

    > The EPS table isn't an ACPI table,
    > it's just a Dell-defined table.

    Hmm... It's either strange or has some background why is so.
    OK it has a note that there is no use case, but here it is!

    Mario, can we consider this as a BIOS bug which doesn't provide SMM
    Communication ACPI table?

    Can it be escalated on UEFI committee?

    --
    With Best Regards,
    Andy Shevchenko

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