[PATCH v5 00/26] fdt: Make OF_BOARD a boolean option

Mark Kettenis mark.kettenis at xs4all.nl
Thu Oct 28 00:30:17 CEST 2021

> From: Simon Glass <sjg at chromium.org>
> Date: Wed, 27 Oct 2021 12:23:21 -0600
> Hi François,
> On Wed, 27 Oct 2021 at 09:14, François Ozog <francois.ozog at linaro.org> wrote:
> >
> >
> >
> > On Wed, 27 Oct 2021 at 16:08, Simon Glass <sjg at chromium.org> wrote:
> >>
> >> Hi François,
> >>
> >> On Tue, 26 Oct 2021 at 00:07, François Ozog <francois.ozog at linaro.org> wrote:
> >> >
> >> > Hi Simon
> >> >
> >> > Position unchanged on this series: adding fake dts for boards that generate their device tree in the dts directory is not good. If you have them in documentation the it is acceptable.
> >>
> >> I think we are going to have to disagree on this one. I actually used
> >> the qemu one in testing/development recently. We have to have a way to
> >> develop in-tree with U-Boot. It does not impinge on any of your use
> >> cases, so far as I know.
> >
> > I am not the only one in disagreement... You just saw Alex Bénée from Qemu saying the same thing.
> > I understand the advanced debug/development scenario you mention.
> > But locating the DT files in the dts directory is mis-leading the contributors to think that they need to compile the DT for the targeted platforms.
> > For your advanced scenario, you can still have the dts in the documentation area, or whatever directory (except dts). compile it and supply to U-Boot.
> We have this situation with rpi 1, 2 and 3 and I don't believe anyone
> has noticed. U-Boot handles the build automatically. If you turn off
> OF_BOARD, it will use the U-Boot devicetree always so you know what is
> going on.

Until.  The Raspberry Pi foundation releases a new firmware that
configures the hardware differently such that the addresses in the
U-Boot devicetree are wrong and nothing works anymore.  Can't speak
for the rpi 1, but this has happened in the past for the rpi 2 and 3
as well as more recently on the rpi 4.

> We can add a message to U-Boot indicating where the devicetree came
> from, perhaps? That might be useful given everything that is going on.
> As in this case, quite often in these discussions I struggle to
> understand what is behind the objection. Is it that your customers are
> demanding that devicetrees become private, secret data, not included
> in open-source projects? Or is it just the strange case of QEMU that
> is informing your thinking? I know of at least one project where the
> first-stage bootloader produces a devicetree and no one has the source
> for it. I believe TF-A was created for licensing reasons...so can you
> be a bit clearer about what the problem actually is? If a board is
> in-tree in U-Boot I would like it to have a devicetree there, at least
> until we have a better option. At the very least, it MUST be
> discoverable and it must be possible to undertake U-Boot development
> easily without a lot of messing around.

How many people are there out there that work on U-Boot that don't
have a Linux source tree checked out?  Even I have several of those
lying around on my development systems and I am an OpenBSD developer ;).

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