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

[Ilias Apalodimas <ilias.apalodimas@linaro.org>]

Hi Krzysztof,

On Tue, Apr 11, 2023 at 07:38:11AM +0200, Krzysztof Kozlowski wrote:
> On 11/04/2023 01:21, jaswinder.singh@linaro.org wrote:
> > From: Jassi Brar <jaswinder.singh@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@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.

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.  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.

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

Thanks
/Ilias

>
> Best regards,
> Krzysztof
>