[PATCH] [RFC]: dtc: Add Kconfig option to pad device tree blob

[Simon Glass]

Hi Eric,

On Tue, 6 May 2025 at 14:50, Eric Schikschneit
<eric.schikschneit at novatechautomation.com> wrote:
>
> Hello Tom,
>
> The link that Simon sent does not add padding at the end. I have tried the approach with SYS_FDT_PAD first and my platform (imx6) still has issues when trying to modify the device tree from the board file. It still returns FDT_ERR_NOSPACE with that option. The commit I sent simply adds a Kconfig option to something we are already doing (passing the -p flag) on multiple platforms behind the scenes to the device tree compiler. I have tested and proven on my platform that this allows live modification of the device tree in the board file.

Is it possible that you have fdt_high environment variable set? That's
the only way I know of that boot_relocate_fdt() can be skipped.

Regards,
Simon


>
> Eric Schikschneit
>
> Senior Embedded Linux Engineer III
>
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> ________________________________
> From: Tom Rini
> Sent: Monday, May 5, 2025 1:09 PM
> To: Simon Glass; Eric Schikschneit
> Cc: u-boot at lists.denx.de
> Subject: Re: [PATCH] [RFC]: dtc: Add Kconfig option to pad device tree blob
>
> On Fri, May 02, 2025 at 08:10:33PM -0600, Simon Glass wrote:
> > Hi Eric,
> >
> > On Fri, 2 May 2025 at 14:06, Eric Schikschneit
> > <eric.schikschneit at novatechautomation.com> wrote:
> > >
> > > This will allow arch(s) that use device tree blobs to pad the end of the
> > > device tree so they can be modified by board files at run time. This will
> > > help prevent errors such as FDT_ERR_NOSPACE from occuring.
> > >
> > > Signed-off-by: Eric Schikschneit <eric.schikschneit at novatechautomation.com>
> > > ---
> > >  arch/Kconfig                 | 11 +++++++++++
> > >  arch/arc/dts/Makefile        |  6 +++++-
> > >  arch/arm/dts/Makefile        |  4 ++++
> > >  arch/m68k/dts/Makefile       |  6 +++++-
> > >  arch/microblaze/dts/Makefile |  6 +++++-
> > >  arch/nios2/dts/Makefile      |  6 +++++-
> > >  arch/powerpc/dts/Makefile    |  4 ++++
> > >  arch/riscv/dts/Makefile      |  6 +++++-
> > >  arch/sandbox/dts/Makefile    |  6 +++++-
> > >  arch/x86/dts/Makefile        |  8 +++++++-
> > >  10 files changed, 56 insertions(+), 7 deletions(-)
> > >
> >
> > This is not a board-specific feature. You could try this:
> >
> > https://patchwork.ozlabs.org/project/uboot/patch/20241206131113.2865416-3-sjg@chromium.org/
>
> Simon, can you please read your links before sending them to other
> people? There's several things wrong with that patch so suggesting
> someone else try it and see is not helpful.
>
> Eric, for your platform can you expand the value used by SYS_FDT_PAD or
> is that not updating things in the correct spot for your use case?
>
> --
> Tom