[PATCH 0/8] An effort to bring DT bindings compliance within U-boot

Krzysztof Kozlowski krzysztof.kozlowski at linaro.org
Fri Dec 15 08:50:51 CET 2023

On 14/12/2023 20:48, Rob Herring wrote:
>> I think some of the important questions to ask are, how often / likely
>> are the breakages to occur? It seems like these days it's either:
>> - U-Boot had an early version of the binding and we already state we
>>   don't support backwards compatibility here. It should be on the
>>   maintainer to be proactive in this case.
>> - It's a "the DT was wrong about the hardware, sorry not sorry it's an
>>   incompatible DTS change now". This too is hopefully the kind of thing
>>   that at least board maintainers will be more actively aware of needing
>>   to deal with in U-Boot, if it's really a problem.
> A common issue in the kernel is with forward compatibility when
> platforms add new resources from a new provider. Then the kernel
> expects a driver for the provider and waits for the dependency. Of
> course, older kernels don't have that provider driver and so the
> dependency is never met. Not sure if u-boot will have similar issues?
> At least you should/could know if the provider driver exists or not.
> (The kernel doesn't because modules.)

If some U-Boot platform decides to aggressively sync with kernel DTS,
then probably the kernel subarch maintainer should be aware of it.
Mentioned forward compatibility issue is a result of assumption that
there are no out-of-tree upstream consumers of our DTS. I am certainly
not aware of any such consumer for Samsung. If someone told me (me
wearing Samsung hat), hey U-Boot now cares, I would start caring as well.

The usual argument of contributors wanting to break the backward and
forward compatibility, is "there is no other OS depending on this"
(recent discussion with Johan about order of interrupts:
https://lore.kernel.org/all/ZWcPZPX-eT-xHAOv@hovoldconsulting.com/ ).
You need to tell the maintainers of that platform, that now they have
other OS/firmware/bootloader depending on DTS compatibility.

Best regards,

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