On Thu, 12 Jul 2018 12:03:05 +0200
Arnd Bergmann [off-list ref] wrote:

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want to be in b) rather than c). An example of this would be
an input device on a PC: If the user operateds the keyboard
or pointer and we have handed off ownership to a sensor hub,
we never get an input event, right?  

Correct. I guess we could try to regain bus ownership in case we have
IBIs enabled. Or we let the secondary master give the bus back to us
when it sees IBIs it can't handle, as described in section 5.1.7:

"
Once granted control of the Bus, the Secondary Master maintains
control until another Master is granted Bus control. After the
Secondary Master transitions to the Current Master role it could
encounter Bus management activities besides the data transfers that it
itself initiates. Some examples are the In-Band Interrupt, or the
Hot-Join request. One optional possibility, shown at Section 5.1.7.2,
is that the Secondary Master performs the Current Master’s actions with
the full capabilities of the Main Master. Another optional possibility
is that the Secondary Master, while serving in the Current Master role,
could defer some actions to a more capable Master, as described in
Section 5.1.7.3.
"  

Ah, so the current master can ask a secondary master to take over
again even if  the secondary master has not requested to be come the
current master?

Yes. Then the inactive master can refuse of course, but it is working
both ways:

- an inactive master can ask for bus ownership
- an active master can ask an inactive one to take over

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I agree. This being said, moving to a representation where the bus is
implicitly represented by the master_controller instance shouldn't be
too difficult. So, if you think we should try this approach I can do
the modifications in my v6.  

I'd say let's wait before you do that change, possibly add a comment
in there now to remind us of what an alternative would be.  

You mean I should keep the i3c_bus object?  

I mean the ongoing discussion shouldn't stop you from posting a v6.

Ok.