[pmbusplus] userspace i2c, pmbus interactions

[Mike Jones]

Jason,

I am interested, because within the PMBus Specification Committee, we are working on a data language intended for device programming. And there is hope that eventually it can become adopted into linux and/or OBMC.

There is a particular use model that is being driven by the IC suppliers and their tools. One reason is that all the vendors have proprietary tools, but they see no competitive advantage, and would rather support a universal standard.

Imagine that programming might be done for:

- ICT
- Proto Builds
- Engineering Bringup
- Remote upgrades

And the context is more than CPU based systems, but includes Networking, other boards with ASICS, etc. So broad context. Hence, it has to work within linux without OBMC.

My view is it is a linux library anyone can use, and OBMC is the piping if it were exposed to a web service, state management, etc.

Now, imagine the IC manufacturer's tool produces a file that can represent a qualified algorithm that is known to work under all possible scenarios, including CRC errors in parts, corrupt NVM, etc. This is what all the vendors do today. They take care of all the things that can go wrong. In the case of ADI, if power was lost while programming, and the BMC or linux can boot from an aux supply, our data files (encoding algorithms), can repair the part under ALL possible random values in the corrupt part.

Furthermore, an integrator (CM, Design House, software team) has to deal with segmented I2C busses, muxes, etc. And the integrator wants to write a wrapper file that integrates all the vendor files. So this integration file has to take care of muxes, order of operations, calling vendor files, etc.

My interest is two part:

1) I am interested in anything that enables our work
2) I am interested in inviting someone from the community, not IC vendor, to our meetings to offer advice and help us define something useful

Mike



> On Apr 23, 2021, at 4:22 PM, Jason Ling <jasonling at google.com> wrote:
> 
> Hi all,
> 
> What started as an attempt to create a simple command line tool to perform pmbus device upgrades over i2c has turned into the start of a user-space i2c library (with some pmbus support).
> 
> I've already reused this library in some other obmc applications and it's been fairly well unit-tested. It also comes with all the public interfaces mocked (so you can unit test your own code).
> 
> The idea is that more and more classes get added that will support different pmbus devices. 
> General idea is that each device that gets support can expose methods to allow device upgrade, black box retrieval, etc..
> 
> Anyways, wanted to gauge community interest in this so I can determine how motivated I should be to upstream it.
>