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

[Rob Herring]

On Thu, Dec 14, 2023 at 12:23 PM Tom Rini <trini at konsulko.com> wrote:
>
> On Thu, Dec 14, 2023 at 03:53:11PM +0100, neil.armstrong at linaro.org wrote:
> > Hi,
> >
> > On 14/12/2023 14:50, Sumit Garg wrote:
> > > Prerquisite
> >
> > s/Prerquisite/Prerequisite/
> >
> > > -----------
> > >
> > > This patch series requires devicetree-rebasing git repo to be added as a
> > > subtree to the main U-boot repo via:
> > >
> > > $ git subtree add --prefix devicetree-rebasing \
> > >        git://git.kernel.org/pub/scm/linux/kernel/git/devicetree/devicetree-rebasing.git \
> > >        v6.6-dts --squash
> >
> > So I think the big question is: when should the subtree be updated ?
> >
> > Because as we discussed in the previous GH pull request, if a bindings changes
> > was made in the upstream Linux DT, then the subtree update should wait until
> > the u-boot support is merged before updating. This could cause a lot of frustration.
> >
> > And this could cause a lot of regressions, even more if both Linux and U-boot are
> > not maintained by the same people.
>
> 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.)

Rob