[RFC PATCH 0/7] arm64: Add fit images for sc7180-trogdor and google,lga

[Simon Glass]

Hi Doug,

Doug Anderson <dianders at chromium.org> wrote:

> Putting the metadata in the configuration's `description` property came
> out of discussions with Michal Simek at LPC 2026 (where Xilinx/AMD
> already uses configuration descriptions for similar board matching).

Thanks for the background. The Xilinx case is a bit different, though:
the same project writes the string (the binman .dts) and parses it
(board.c), so it can change both sides together. Here the kernel would
write the string and the Pixel bootloader and outside packaging tools
would parse it. That makes it a cross-project ABI, and I'd rather that
ABI were typed properties than an unwritten string format.

> The proposal I've tried to push a few times is that it's OK that
> different loaders have different types of information available
> to them, but people don't like that. They want a universal standard,
> which nobody can come up with.

I agree with you here. We don't need a universal set. I've sent a
proposed spec change [1] which lets a configuration node hold one or
more match sub-nodes. Each one names its scheme with a vendor-prefixed
compatible string and carries the properties that scheme defines, for
example:

    conf-1 {
        compatible = "google,lga-...";
        ...
        match-1 {
            compatible = "google,board-id";
            board-id = <...>;
            board-rev = <...>;
            soc-id = <...>;
            soc-rev = <...>;
        };
    };

Trogdor would use its own scheme (board name as a string, rev and SKU
as u32), and Michal's loader could do the same. Each loader still gets
what it needs, the types are explicit, and nobody has to parse
'description'. Please can you take a look and comment there? If it
works for you, you can point to it in v2.

> Should I give it a shot for v2?

Yes please. The DTB list already reaches make_fit.py from the Makefile
through the @file argument, so the new file only has to say which DTBs
to include and what metadata each one gets. We'll need a simple
per-platform file next to the .dts files, passed with a new option
through FIT_EXTRA_ARGS

Running fdtfactor can then be another make_fit.py option, like --decompose-dtbs

[1] https://github.com/open-source-firmware/flat-image-tree/pull/66

Regards,
Simon