Re: [PATCH v5 06/26] arm: qemu: Add a devicetree file for qemu_arm64

[Tom Rini <trini@konsulko.com>]

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On Mon, Nov 01, 2021 at 06:33:35PM +0100, François Ozog wrote:
> Hi Simon
> 
> Le lun. 1 nov. 2021 à 17:58, Simon Glass <sjg@chromium.org> a écrit :
> 
> > Hi Peter,
> >
> > On Mon, 1 Nov 2021 at 04:48, Peter Maydell <peter.maydell@linaro.org>
> > wrote:
> > >
> > > On Tue, 26 Oct 2021 at 01:33, Simon Glass <sjg@chromium.org> wrote:
> > > >
> > > > Add this file, generated from qemu, so there is a reference devicetree
> > > > in the U-Boot tree.
> > > >
> > > > Signed-off-by: Simon Glass <sjg@chromium.org>
> > >
> > > Note that the dtb you get from QEMU is only guaranteed to work if:
> > >  1) you run it on the exact same QEMU version you generated it with
> > >  2) you pass QEMU the exact same command line arguments you used
> > >     when you generated it
> >
> > Yes, I certainly understand that. In general this is not safe, but in
> > practice it works well enough for development and CI.
> 
> You recognize that you hijack a product directory with development hack
> facility. There is a test directory to keep things clear. There can be a
> dev-dts or something similar for Dev time tools.
> I have only seen push back on those fake dts files in the dts directory: I
> guess that unless someone strongly favors a continuation of the discussion,
> you may consider re-shaping the proposal to address concerns.

Yes.  We need to document how to make development easier.  But I'm still
not on board with the notion of including DTS files for platforms where
the source of truth for the DTB is elsewhere.  That's going to bring us
a lot more pain.

It is important to make sure our "develop our project" workflow is sane
and relatively pain free.  But that needs to not come by making
sacrifices to the "use our project" outcome.  I would hope for example
that the new Pi zero platform is just dtb changes, as far as the linux
kernel is concerned which means that for rpi_arm64 (which uses run time
dtb) it also just works.  And that's what we want to see.

-- 
Tom

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