[TrouSerS-users] General implementation questions

[Jared D S. <jsc...@bi...>]

Hello,

These questions don't pertain directly to the TSS but they are related.

1.) The low pin-count bus has signals that support interrupt generation and
direct memory access. To my knowledge, the TPM is not allowed to directly
access memory (for security reasons). Is this true? Also, does the TPM not
support interrupts simply because of manufacturing costs?

2.) Does the TPM support bidirectional data transfer? Can it write out the
result out the byte stream resulting from the last operation as it reads in
the next? I'm wondering what triggers the tcsd to start sending the next
command (the beginning of the response packet or its end).

3.) What algorithm does the tcsd use to order requests to the TPM? I would
assume that the simplest algorithm is the order in which they are received,
but it may be something more along the lines of round robin with respect to
user applications.

If the answer to any of these questions is "because the TPM specification is
not strict about X and Y" or "it's up to the manufacturer", then feel free
to say that (although it would be helpful to know what the industry common
practice is in those cases). I'm pretty familiar with the TrouSerS spec, but
I haven't looked much into that of the TPM.

Thanks,
Jared