Plans for BMC i2c to host bridge via IPMI

[Peter Hanson]

Ave!

This email captures proposed actions from an exchange earlier today on
the #openbmc IRC channel.

Basic goal is to reach devices on a BMC I2C bus from IPMI commandline at host.

I2C commands and responses to be carried as OEM extension messages,
i.e., Network Function Codes 2Eh / 2Fh in the Intel specification.
Those message forms require a three byte IANA Enterprise Number, and
our original plan used Google's code.

We would like to carry the feature in OpenBmc, so I wanted to confirm
if this is acceptable, and/or what modifications would be needed.

Decisions:

1. Ok to use OEM extensions. Patrick noted that OpenBmc already uses
some, albeit under the IBM IANA Enterprise Number.

2. Switch to OpenBmc IANA Enterprise Number when available.

3. Patrick proposed to create a new phosphor-ipmi-oemproviders repo to
hold the code, message documentation, etc.

4. All uses of the OpenBmc IANA shall be enumerated in place - almost
certainly an include file in the new repo - so we don't end up with
conflicting uses.

Actions:

A1. peterh: send this email to the mailing list.
A2. stwcx: request IANA Enterprise Number.
A3. stwcx: create new phosphor-ipmi-oemproviders repo.
A4. peterh+brendanhiggins: propose detailed message designs.
A5. peterh: {net-ipmid,host-ipmi} += support for these commands.

A key point of this email is to reap your collective wisdom, so please
if you have something to contribute, please do. In particular,
Patrick, please correct anything I misunderstood or incorrectly
extrapolated from the chat.

  -- peterh