Supporting one IPMI request does not yield one response

[Brendan Higgins]

Hello,
The reason I am interested in having support for not requiring one response
to be tied to one request is because I am interested in multiple responses
being associated with a single request. In particular, I am interested
adding an OEM Group extension that allows arbitrarily large payloads to be
broken up across multiple Block Transfer messages.

I have a prototype for this OEM Group extension that I have tested on the
Aspeed 2500 EVB; there are some changes that need to be made to the handler
code in phosphor-host-ipmid to make it work, but nothing that seemed to
have any potential for controversy other than allowing a single request to
solicit none-to-many responses. There are other ways to make this work, but
this seemed to be the most palatable to me for the reason that it generates
less traffic than having to send a dummy request to get each of the
responses after the first one or using something like SMS Attention. I also
thought that the OpenBMC community might find supporting one request
soliciting multiple responses to be interesting because it would add the
capability to support IPMI Message Bridging as it requires sending two
responses for a single request (see '6.13.4 Bridged Request Example' in the
IPMI spec).

The OEM Group extension I mentioned could be thought of as a transport
layer over IPMI; it is something that I would like to get some more
feedback on later at which time I will send a more specific email detailing
how it works. Right now, I am just interested in whether there is any
interested in allowing a single IPMI request to solicit none-to-many
responses.

Feedback is greatly appreciated!

Thanks!
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