Re: [dmidecode] [PATCH] dmioem: Decode HPE OEM Record 224

[Jean Delvare]

On Mon, 27 Jun 2022 14:28:44 -0600, Jerry Hoemann wrote:
> On Thu, Jun 23, 2022 at 01:20:54PM +0200, Jean Delvare wrote:
> > For my own enlightenment, what does "Option ROM Measuring" mean?  
> 
> In this context TPM measurements are essentially checksums of a 
> thing.  In this case it's the Option ROM. So this tells if the system in
> its current configuration is measuring the option rom or not.
> (A message is actually printed during POST for this.)

OK, thanks for the explanation.

> > (...)
> > There's some repeated arithmetic here that could be avoided. Either
> > access the bits directly:
> > 
> >     pr_attr("Standard Algorithm Supported", "%s", code & (1 << 4) ? "Yes" : 
> > "No");  
> 
> How about:
> 
>       pr_attr("Standard Algorithm Supported", "%s", (code & (1 << 4)) ? "Yes" 
> : "No");

Yeah, sure.

> > (...)
> > I also don't really understand how "Standard" opposes itself to
> > "Pluggable" thus can't really make sense of the "but" between them.  
> 
> Sans typo, this is directly from the spec.
> 
> The physical nature of the TPM on proliant systems has been evolving and
> can vary based upon system.  The vision (as I understand it) roughly speaking 
> is:
> 
> Phase one, the TPM was a could be added my customers, hence plugable.
> For example:
> 
> https://techlibrary.hpe.com/docs/iss/DL380_Gen10/setup_install/GUID-4D7C8B58-F938-4A6B-B0E2-D5EFDFCCBF07.html#GUID-4D7C8B58-F938-4A6B-B0E2-D5EFDFCCBF07
> 
> The coffin that one puts over the TPM adds tamper resistence to the
> device.
> 
> Phase two, the device was essentially the same, but was to be
> a standard feature (i.e. installed by the factory.)
> Hence, "Plugable but Standard"
> 
> The third phase would be a TPM was soldered down on the motherboard.
> 
> Having said this, I'm not sure to what extent this vision was realized
> or if FW is reporting it correctly.  All systems that I have access to
> that have TPM show as "Plugable and Optional."

OK, thanks for the explanation. I'm fine keeping the wording as it is
in your specs to follow the principle of least surprise for your
customers.

-- 
Jean Delvare
SUSE L3 Support