[PATCH v2 15/18] fdt: Allow the devicetree to come from a bloblist

[Simon Glass]

Hi Raymond,

On Mon, 4 Dec 2023 at 12:25, Raymond Mao <raymond.mao at linaro.org> wrote:
>
> Hi Simon,
>
> When `OF_BOARD` is defined, the FDT should be from one of  the board-specific mechanisms:
> 1. FDT from a bloblist via boot args
> 2. FDT in memory
> I don't think we need a new build option to distinguish these two, since it can be done in runtime by checking whether the boot args follow the FW Handoff spec conventions and the FDT exists in the bloblist.

No, I would really like this to be deterministic, so we can fail if
something goes wrong. The bloblist should be 'declared' as the way to
boot, for a board.

If in the future all boards a reusing bloblist for this feature, then
sure, we can drop it. But we have things like rpi which do their own
thing.

> If it fulfills the above conditions, we can take the FDT from bloblist, otherwise from the predefined memory address.
> This is fully backward compatible without adding a new build option.

Again, we need to obtain the FDT from the bloblist if and only if the
board requires it. It creates a lot of confusion to have it as an
optional feature, when we know which way it should be.

Ultimately OF_BOARD should go away. We just need to push bloblist to
other projects and closed-source firmware as the correct way to pass a
DT.

Regards,
Simon
[.]