[PATCH v3 0/7] Add FIT multi-DTB selection for Qualcomm platforms

[Jan Kiszka]

On 01.05.26 08:54, Sumit Garg wrote:
> Hi Jan,
> 
> On Fri, Apr 17, 2026 at 02:15:43PM +0200, Jan Kiszka wrote:
>> On 17.04.26 14:09, Aswin Murugan wrote:
>>> This series adds dynamic device tree selection from FIT images for
>>> Qualcomm Snapdragon platforms, enabling U-Boot to select the
>>> appropriate DTB based on hardware parameters detected from SMEM.
>>>
>>> Qualcomm fit based DTB format is documented in [1]
>>> The fit image contains only DTB, while the kernel will be part of UKI image.
>>>
>>
>> I suppose you know that UKIs (systemd-boot, EFI Boot Guard) provide DTB
>> selection as well. However, that is a fix-up for the case the firmware
>> does not provide a fitting DTB. This here is supposed to support the
>> firmware DTB delivery, correct?
>>
> 
> I would say instead that it's an alternate way to bundle multiple DTBs
> in a specific DT partition which are used by firmware to select
> appropriate DTB for the board the firmware is running on.

Right. We (and likely not only us) implemented that kind of DTB
selection many years ago for the IOT2050 boards with existing U-Boot
features here. But we embedded the supported DTBs into the U-Boot FIT
image so that they naturally become part of the secure boot chain.

> 
> The source of this DTBs are from kernel only where the OEM has to take
> care of 1:1 compatibility among kernel and DTB. This approach has been
> deployed for Yocto and Android based systems but I do agree with general
> purpose distros bundling DTBs in UKIs is surely an alternative option.

This is just a workaround for broken vendor firmware or vendor kernels.
In the ideal world, the firmware delivers an upstream-approved DTB to an
upstream kernel. Any update of firmware or kernel only augments bindings
and DTBs, adding features or refining them in a compatible way, not
breaking them - SystemReady.

In real world, premature vendor code gets shipped first and only cleaned
up later on via upstream (if at all). Then you need to fix up the
mismatches between in-field firmware and upstreamed kernels. And all
that obviously in secure, updatable way, therefore UKI embedding.

Jan

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