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

[Michal Simek]

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

> 
> 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.

Thanks,
Michal