Re: [PATCH 0/3] dt-bindings: arm: qcom: define schema, not devices

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 25/07/2022 19:22, Doug Anderson wrote:
>>>> You cannot do that...
>>>
>>> The bootloader never falls back to just the SoC name.
>>
>> There is no "SoC" part of compatible list. Only by convenience we put it
>> that way, but DT spec does not define first compatible to be for
>> platform because they all are[1], therefore following your earlier
>> description - bootloader should load BAR DTS on FOO device just because
>> qcom,sdm845 matches.
> 
> As documented in "Documentation/arm/google/chromebook-boot-flow.rst",
> the bootloader creates a match list to pick a device tree file. It
> never creates a match list that has just the SoC. It always picks
> based on the board name and never falls back to just the SoC name.

So this means you embedded some custom-interpretation of board
compatibles in bootloader. What stops you to customize it even more,
that the bootloader must always pick the most specific compatible? IOW,
it cannot load DTB from more generic compatible (just like it should not
load qcom,sdm845 DTS)?

I understand the limitation of board compatibles for your case, but I
still believe it is wrong usage of it.
If the usage - by principle - was correct, then you would not need to
add the restriction you mentioned above ("never creates a match list
that has just the SoC").

Because when Linux drivers match, they do not have such restriction...

Best regards,
Krzysztof