[PATCH] dt/bindings: fwu-mdata-mtd: drop changes outside FWU

[Krzysztof Kozlowski]

On 03/05/2023 16:37, Ilias Apalodimas wrote:
> Hi Krzysztof,
> 
> On Tue, Apr 11, 2023 at 07:38:11AM +0200, Krzysztof Kozlowski wrote:
>> On 11/04/2023 01:21, jaswinder.singh at linaro.org wrote:
>>> From: Jassi Brar <jaswinder.singh at linaro.org>
>>>
>>> Any requirement of FWU should not require changes to bindings
>>> of other subsystems. For example, for mtd-backed storage we
>>> can do without requiring 'fixed-partitions' children to also
>>> carry 'uuid', a property which is non-standard and not in the
>>> bindings.
>>>
>>>  There exists no code yet, so we can change the fwu-mtd bindings
>>> to contain all properties within the fwu-mdata node.
>>>
>>> Signed-off-by: Jassi Brar <jaswinder.singh at linaro.org>
>>> ---
>>>
>>> Hi Rob, Hi Krzysztof,
>>>
>>>   I was suggested, and I agree, it would be a good idea to get your blessings
>>> for the location and meta-data (fwu-mdata) bindings for the FWU.
>>>
>>>   The FWU images can be located in GPT partitions or MTD backed storage.
>>> The basic bindings for fwu-mdata has already been merged in uboot (ideally they
>>> too should have had your review). Now I am trying to fully support MTD backed
>>> storage and hence looking for your review. The proposed bindings are totally
>>> self-contained and don't require changes to any other subsystem.
>>>
>>> Thanks.
>>
>> I think we do not review U-Boot bindings usually, except these put in
>> the Linux kernel. There were few targeting U-Boot specifically (e.g.
>> Documentation/devicetree/bindings/mtd/partitions/u-boot.yaml and
>> Documentation/devicetree/bindings/nvmem/u-boot,env.yaml) so if you want
>> our blessing, the bindings should be done in Linux kernel repo.
>>
>> I am pretty sure that reviewing other project bindings would be too much
>> of work for me.
> 
> Sure that makes sense.  But an answer here of whether the bindings make
> sense to the DT maintainers or not would help to move forward.

I am not a DT maintainer of other systems, components etc. Answering
anything for these other systems and components means nothing. I will
take no responsibility of whatever I say because I will bear no costs of
it. :) IOW, to me you can make any invalid binding inside U-Boot and it
will not matter for the Linux kernel. It will of course matter to U-Boot
in many aspects.

> 
> These bindings are trying to define a standardized interface for A/B *firmware*
> updates [0] which is not what traditionally goes into a device tree.  OTOH we
> already have some U-Boot specific bindings as you already mentioned.  As we
> move forward we need to be very precise on what is allowed or not on the DT
> since it's now tested and verified on SystemReady certifications.
>  IOW if
> we add those binding in U-Boot only, we would need to strip them before
> handing the DT to linux, otherwise certification would fail.

Which you can.

Or propose to add the bindings to the Linux kernel and to the Linux
kernel DTS, which then will get our review.

>  If you do
> think that having them in the kernel repo makes sense,  it would help
> standardizing other boot loaders (at least it would standardize where that
> metadata lives) if they want to implement something similar.

I cannot speak for Rob, but that's the only way I can make a review. I
cannot review or try to maintain all possible projects in the world and
their bindings. How would this even work in practice?

> 
> Just keep in mind we would need a schema per storage medium.  IOW this tries to
> standardize devices which keep the firmware binary in an mtd.  There's also
> another biding which describes firmware files on a GPT [1].
> 
> [0] https://developer.arm.com/documentation/den0118/a
> [1] https://source.denx.de/u-boot/u-boot/-/blob/master/doc/device-tree-bindings/firmware/fwu-mdata-gpt.yaml

Best regards,
Krzysztof