On Mon, Jun 18, 2018 at 9:45 AM, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > This is a proposal for how to handle the non-discoverable > 96boards plug-in expansion boards called "mezzanines" in the > Linux kernel. It is a working RFC series meant for discussion > at the moment. > > The RFC was done on the brand new Ultra96 board from Xilinx > with a Secure96 mezzanine expansion board. The main part > is in patch 4, the rest is enabling and examples. > > The code can be obtained from here: > https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-integrator.git/log/?h=ultra96 > > You can for example probably augment the DTS file for any > upstream-supported 96board and get the Secure96 going with > it with minor efforts. Hi Linus, Thanks for your work on solving this long-standing problem. I've just read through your patches briefly and have a few thoughts: - 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. - 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. - 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. 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. Arnd -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
