[PATCH 30/32] fdt: Allow the devicetree to come from a bloblist

[Ilias Apalodimas]

[...]

> >
> > > +config OF_BLOBLIST
> > > +     bool "DTB is provided by a bloblist"
> > > +     help
> > > +       Select this to read the devicetree from the bloblist. This allows
> > > +       using a bloblist to transfer the devicetree between  U-Boot phases.
> > > +       The devicetree is stored in the bloblist by an early phase so that
> > > +       U-Boot can read it.
> > > +
> >
> > I dont think this is a good idea.  We used to have 4-5 different options
> > here, which we tried to clean up and ended up with two very discrete
> > options.  Why do we have to reintroduce a new one?  Doesn't that bloblist
> > have a header of some sort?  The bloblist literally comes from a previous
> > stage bootloader which is what OF_BOARD is here for. So why can't we just
> > read the header and figure out if the magic of the bloblist matches?
>
> No, OF_BOARD is a hack to allow boards to do what they like with the FDT.
>
> This patch is a standard mechanism to pass the DT from one firmware
> phase to the next. We have spent quite a bit of time creating a spec
> for it, and we should use it.

Where exactly am I objecting using the spec?   Can you please re-read my email?
I am actually pointing out we should use the spec *properly*.  So
instead of having a Kconfig option for the DT, which is pretty
pointless,  we should parse the bloblist.  If the header defined by
the *spec* is found, we should just search for the DT in there.
What you are doing here, is take the spec, pick a very specific item
that the list contains, and create a Kconfig option out of it.  Which
basically ignores the discoverable options of the bloblist.  For
example, that bloblist can also contain an entry to a TPM eventlog.
Should we start creating Kconfig options for all the firmware handoff
entries that are defined on that spec?

Thanks
/Ilias

>
> The patches to align bloblist with the spec have been sent, but there
> is a late-breaking change that we are trying to resolve. Once that is
> sorted out, I will send v2 of those patches.
>
> >
> > >  config OF_BOARD
> > >       bool "Provided by the board (e.g a previous loader) at runtime"
> > >       default y if SANDBOX || OF_HAS_PRIOR_STAGE
> > > diff --git a/include/bloblist.h b/include/bloblist.h
> > > index 080cc46a126..e16d122f4fb 100644
> > > --- a/include/bloblist.h
> > > +++ b/include/bloblist.h
> > > @@ -103,6 +103,11 @@ enum bloblist_tag_t {
> > >       BLOBLISTT_ACPI_TABLES = 0x104,  /* ACPI tables for x86 */
> > >       BLOBLISTT_SMBIOS_TABLES = 0x105, /* SMBIOS tables for x86 */
> > >       BLOBLISTT_VBOOT_CTX = 0x106,    /* Chromium OS verified boot context */
> > > +     /*
> >
> > [...]
> >
> > >
> > [0] https://github.com/FirmwareHandoff/firmware_handoff
>
> Regards,
> Simon