On Mon, 31 Jul 2017 21:17:45 +0200
Wolfram Sang [off-list ref] wrote:

Hi Boris,

quoted

This patch series is a proposal for a new I3C [1] subsystem.  

Nice. Good luck with that!

Some hi-level comments from me related to I2C. I can't say a lot more
because the specs are not public :(

quoted

- the bus element is a separate object and is not implicitly described
  by the master (as done in I2C). The reason is that I want to be able
  to handle multiple master connected to the same bus and visible to
  Linux.
  In this situation, we should only have one instance of the device and
  not one per master, and sharing the bus object would be part of the
  solution to gracefully handle this case.
  I'm not sure if we will ever need to deal with multiple masters
  controlling the same bus and exposed under Linux, but separating the
  bus and master concept is pretty easy, hence the decision to do it
  now, just in case we need it some day.  

From my experience, it is a good thing to have this separation.

quoted

- I2C backward compatibility has been designed to be transparent to I2C
  drivers and the I2C subsystem. The I3C master just registers an I2C
  adapter which creates a new I2C bus. I'd say that, from a
  representation PoV it's not ideal because what should appear as a
  single I3C bus exposing I3C and I2C devices here appears as 2
  different busses connected to each other through the parenting (the
  I3C master is the parent of the I2C and I3C busses).
  On the other hand, I don't see a better solution if we want something
  that is not invasive.  

I agree this is the least invasive and also the most compatible
approach. The other solution would probably be to have some kind of
emulation layer?

quoted

I'd also like to get feedback on the doc. Should I detail a bit more
the protocol or the framework API? Is this the kind of things you
expect in a subsystem doc?  

Since the spec is not public, details about the protocol will be
especially useful, I'd say.

MIPI has opened the I3C spec [1], it can be downloaded here [2].

v2 of this series will come soon (sorry for the delay).

Regards,

Boris

[1]https://www.businesswire.com/news//home/20171212005059/en/MIPI-Alliance-Opens-Access-MIPI-I3C-Sensor
[2]http://resources.mipi.org/mipi-i3c-v1-download