[PATCH] binman: Add option for pointing to external description

[Simon Glass]

Hi Michal,

On Wed, 16 Oct 2024 at 00:00, Michal Simek <michal.simek at amd.com> wrote:
>
> Hi Simon,
>
> On 10/15/24 14:48, Simon Glass wrote:
> > Hi Michal,
> >
> > On Thu, 10 Oct 2024 at 07:03, Michal Simek <michal.simek at amd.com> wrote:
> >>
> >>
> >>
> >> On 10/9/24 23:14, Simon Glass wrote:
> >>> Hi Michal,
> >>>
> >>> On Wed, 9 Oct 2024 at 07:21, Michal Simek <michal.simek at amd.com> wrote:
> >>>>
> >>>> Hi,
> >>>>
> >>>> On 10/9/24 03:55, Simon Glass wrote:
> >>>>> Hi Michal,
> >>>>>
> >>>>> On Mon, 7 Oct 2024 at 07:05, Michal Simek <michal.simek at amd.com> wrote:
> >>>>>>
> >>>>>> Adding binman node with target images description can be unwanted feature
> >>>>>> but as of today there is no way to disable it.
> >>>>>> Also on size constrained systems it is not useful to add binman description
> >>>>>> to DTB.
> >>>>>> Introduce BINMAN_EXTERNAL_DTB Kconfig symbol which allows separate DTB for
> >>>>>> target from DTB for binman itself.
> >>>>>>
> >>>>>> Signed-off-by: Michal Simek <michal.simek at amd.com>
> >>>>>> ---
> >>>>>>
> >>>>>>     Makefile    |  2 +-
> >>>>>>     lib/Kconfig | 10 ++++++++++
> >>>>>>     2 files changed, 11 insertions(+), 1 deletion(-)
> >>>>>>
> >>>>>
> >>>>> Doesn't this defeat one of the purposes of Binman, i.e. to document
> >>>>> images? We do want the .dts to include the image description. What
> >>>>> sort of problem is this causing?
> >>>>
> >>>> We have two boot flows.
> >>>> The first one (default one) is using Xilinx FSBL for SOM initialization with fit
> >>>> image (DTBS) + u-boot.elf + tfa.
> >>>>
> >>>> The second one is using U-Boot SPL instead of FSBL. This flow is used by
> >>>> buildroot for example.
> >>>>
> >>>> In perfect world I should describe both of these flows. I sent description for
> >>>> the second as RFC here.
> >>>> https://lore.kernel.org/r/de1b8dbabd5ab7f20d7aac217ec4f5074d39f1da.1728462767.git.michal.simek@amd.com
> >>>
> >>> OK I'll take a look.
> >>>
> >>>>
> >>>> but it is also reasonable to describe the first flow but I really don't want
> >>>> both descriptions ends up in the target image.
> >>>
> >>> Why not? Knowing what is in the firmware is one of the goals of Binman.
> >>
> >> If this is single binary composition with clear layout then likely fine.
> >> In our case where we target evaluation boards which can boot out of different
> >> boot devices it will be more confusing.
> >> For these I want to generated all images also for testing purpose not only
> >> images which you will burn to qspi.
> >>
> >>>>
> >>>> The second part is if you look at RFC and how fit-dtb.blob is composed. It is
> >>>> one DTB + DTBS which are composed from overlays.
> >>>>
> >>>> xilinx_zynqmp_kria_defconfig has
> >>>> CONFIG_DEFAULT_DEVICE_TREE="zynqmp-smk-k26-revA"
> >>>>
> >>>> That's why binman node should go to this DTB but because other images are
> >>>> composed with overlays binman node is spread to all DTBs inside FIT image.
> >>>>
> >>>> It means one binman description is in fit-dtb.blob 14 times which is far from
> >>>> ideal.
> >>>
> >>> Yes, but I think what you are saying is that U-Boot doesn't need the
> >>> description, so you don't need it to appear in the dtbs in the FIT. Is
> >>> that right?
> >>
> >> Yes.
> >> I know that there is a code around it but as of now I don't want to use any of
> >> this feature.
> >>
> >>> If so, then I think we should add a way to remove it, in Binman,
> >>> perhaps with a property in the top-level binman image.
> >>
> >> Works for me but keep in your mind that for SOM this should be removed from all
> >> combinations and for me it is easier not to add that description there instead
> >> of adding it and removing it.
> >
> > OK, I think you are saying that the description is repeated in each
> > .dtb since each is built by U-Boot's build system and then they are
> > added to the FIT.
>
> yep

OK, got it. I think we should add an way to make the binman node optional.

>
> >
> > But what is to stop people from not bothering to fill in the binman
> > description in U-Boot? I worry that vendors will have instructions
> > like 'build U-Boot with the in-tree devicetree, which has no binman
> > node, but pass this option to use this other file (not in mainline,
> > just our special vendor branch), just for Binman's use',
> >
> > Where do you plan to keep this other file?
>
> In u-boot repo of course. And all configurations which makes sense.
> And pretty much if vendors wants to hide it they can no matter of this patch.
> I understand your concern but vendors can do it today.

So what value are you going to use for BINMAN_EXTERNAL_DTB ? Is there
a patch for that? Perhaps it should be renamed, since it suggests that
the file is out of tree.

Regards,
Simon