On Mon, Jun 18, 2018 at 2:21 PM Arnd Bergmann [off-list ref] wrote:

- I really like the idea of having C code deal with the mezzanine
  connector itself, acting as an intermediate to tie a number of
  boards to a number of add-on cards, this seems much simpler than
  trying to do everything with overlays or one of the other more
  generic mechanisms.

This is my point of view as well.

- I don't like the idea of having the bus driver contain a list of possible
  add-ons, this seems to go against our usual driver model. What
  I think we want instead is to make the connector itself a proper
  bus_type, to allow drivers to register against it as loadable modules,
  and devices (maybe limited to one device) being created as probed
  from DT or some other method as you describe.

OK I think I can do that. It will take some thinking and I would
guess I should also move it to drivers/platform/*

My idea here would be to have a connector bus that some random
add-on (such as a 96board mezzanine) would probe to, so we
make it generic for any connector plug.

- You export symbols in the mezzanine_* namespace, which I think
   is a bit too generic and should perhaps contain something related
   to  96boards in its name to make it less ambiguous. I suspect we
   would add a number of further connectors for hats, capes, lures etc,
   which could all be described as mezzanines.

Michal also brings up the (discoverable!) FMC connectors Xilinx are
using. So the idea would be to create something generic to help
probe and populate them all whether partly discoverable or not.

   One open question
   is how we structure the commonality between the various
   connectors, but we can defer that until we have more than one
   or two of them.

I can clean up the namespace at least so it gets clear where to
add them. I will try to be more generic in the next iteration.

Yours,
Linus Walleij