Re: [ImageBuilder 0/2] Use lopper to generate partial dts

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 13 Sep 2022, Michal Orzel wrote:
> Hi Ayan,
> 
> On 12/09/2022 18:27, Ayan Kumar Halder wrote:
> > Hi Michal,
> > 
> > On 12/09/2022 12:59, Michal Orzel wrote:
> >> This patch series introduces support to generate automatically passthrough
> >> device trees using lopper. This feature should be used with care as the
> >> corresponding lopper changes are still in an early support state. Current
> >> integration has been tested with several devices from ZynqMP ZCU102 board
> >> e.g. serial, spi, ahci, mmc.
> >>
> >> When using this feature, make sure to use the latest lopper's master branch
> >> status [1].
> > 
> > I am guessing that this is the first time the imagebuilder is using 
> > script from an external repo. There might always be a possibility that 
> > future changes to lopper (master branch) might not be backward 
> > compatible or might break something in imagebuilder.
> > 
> > As such, will it make things better if lopper is included as a 
> > gitsubmodule for imagebuilder. This way a specific revision of lopper 
> > will be in sync with a specific revision of imagebuilder.
> > 
> > Please let me know your thoughts.
>
> I think it could be beneficial in the future but not in the current state.
> The reason why is that the lopper changes are in an early support state
> (I try to highlight it on each occasion). This means that in the near
> future we will be improving lopper extract assists to cover some corner cases.
> Adding lopper as a submodule now, would result in a need of additional commits
> for the ImageBuilder fetching new lopper changes each time we improve 
> something
> in lopper. I think we do not need such overhead at this stage.
> 
> Also lopper's README states that "Internal interfaces are subject to change"
> so we can assume that the interface given to the user will not change.

Forward and backward compatibility is something we'll need to think
about at some point.

Personally I dislike git submodules and I would try to avoid using them
unless strictly necessary. However, we could specify a commit-id or tag
to use (the same way Yocto specifies component versions.)

Given that it is still early stage for this feature, I think we could
ignore the problem for now and come back to it in the future.

Or we could change this patch series now to take as LOPPER_PATH input
something like a SRC_URI in Yocto, which could be any of the following:

git://some.host/somepath;branch=branchX,branchY;name=nameX,nameY
https://some.host/somepath;branch=branchX,branchY;name=nameX,nameY
file://local.path/to/file.txt

If we did this, it would be more future proof and we could use the
https:// URI by default with the "master" or "master-next" branch so
that we would automatically get the latest updates. In the future we
would specificy a stable branch instead (e.g. v0.2022.x).