[PATCH v4] fdt: Allow the devicetree to come from a bloblist

[Simon Glass]

Hi Ilias,

On Wed, Dec 27, 2023 at 6:44 AM Ilias Apalodimas
<ilias.apalodimas at linaro.org> wrote:
>
> Hi Tom,
>
> On Tue, 26 Dec 2023 at 14:07, Tom Rini <trini at konsulko.com> wrote:
> >
> > On Tue, Dec 26, 2023 at 09:46:25AM +0000, Simon Glass wrote:
> >
> > > Standard passage provides for a bloblist to be passed from one firmware
> > > phase to the next. That can be used to pass the devicetree along as well.
> > > Add an option to support this.
> > >
> > > Tests for this will be added as part of the Universal Payload work.
> > >
> > > Signed-off-by: Simon Glass <sjg at chromium.org>
> > > ---
> > > The discussion on this was not resolved and is now important due to the
> > > bloblist series from Raymond. So I am sending it again since I believe
> > > this is a better starting point than building on OF_BOARD
> >
> > I really don't like adding another option for "DT is given to us". Why
> > isn't adding another enum to fdt_source_t sufficient, and if we have
> > bloblist enabled, that will look for and use if found? Maybe some other
> > code needs to be restructured and cleaned up too?
>
> Same here. On top of that the bloblist has a few items in there, e.g a
> TPM eventlog. What are we going to do? Add a Kconfig for each item?

No, but that is just a straw man. The DT is special and U-Boot reports
where it comes from.

>
> This has been going back and forth for a while. I've lost count of how
> many times I repeated the same proposal, but here it goes again. We
> have OF_BOARD and BLOBLIST options. The bloblist and its properties
> are scannable at runtime. Can't we use the combination of these 2 can
> be used to imply we expect things from a bloblist. If we want to be
> stricter in the future and explicitly expect the DT from a bloblist,
> we could add a Kconfig option failing the boot if that's missing.

I would like to have that Kconfig option now, not later. In my mind,
the boot must be deterministic, so that if OF_BLOBLIST is enabled, the
DT must come from there, or it is an error.

Also, repeating it doesn't make the proposal good. We agreed that
OF_BOARD would eventually go away, so building on top of it is not
setting us up for the future.

Regards,
Simon