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Re: [dmidecode] [Patch v3] firmware: dmi-sysfs: add SMBIOS entry point a

From: Jean Delvare
Subject: Re: [dmidecode] [Patch v3] firmware: dmi-sysfs: add SMBIOS entry point area raw attribute
Date: Sun, 8 Mar 2015 18:11:40 +0100

On Sun, 8 Mar 2015 14:53:04 +0100, Ard Biesheuvel wrote:
> On 8 March 2015 at 12:31, Jean Delvare <address@hidden> wrote:
> > On Sat, 07 Mar 2015 22:53:32 +0200, Ivan.khoronzhuk wrote:
> >> The specification doesn't oblige firmware to provide two entry points.
> >> An implementation may provide either the 32-bit entry point or the 64-bit
> >> entry point, or both. For compatibility with existing SMBIOS parsers, an
> >> implementation should provide the 32-bit entry point, but it's not 
> >> required.
> >
> > I expect most implementations will do, as it's trivial to implement.
> Not quite. First of all, some 64-bit ARM systems do not have any
> system RAM below 4 GB, so there is not way they can implement the
> 32-bit entry point.

I didn't know that, thanks for the notice. No big deal anyway, these
systems did not support SMBIOS before version 3.0 so there cannot be
any regression on these systems.

> Also, the 64-bit entry point does not limit the
> structure size or the entire table to 64 KB like the 32-bit one does,
> so it may be necessary to create a whole separate table with a subset
> of the contents of the real table to stay within limits for the 32-bit
> entry point.

I doubt this is an issue in practice. I have been around for quite some
time now and the largest table I've ever seen was 9043 byte long, which
is nowhere close to the limit.

> And the 32-bit entry point could well be 3.0 anyway, if
> it uses any of the new enum values for the data items that were
> undefined before 3.0.

This is true but irrelevant to the discussion.

Jean Delvare
SUSE L3 Support

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