[PATCH v2] emulation: fdt: Allow using U-Boot's device tree with QEMU

[Tom Rini]

On Thu, Apr 17, 2025 at 03:39:57PM -0600, Simon Glass wrote:
> Hi Tom,
> 
> On Mon, 14 Apr 2025 at 16:53, Tom Rini <trini at konsulko.com> wrote:
> >
> > On Sun, Apr 06, 2025 at 07:07:04AM +1200, Simon Glass wrote:
> >
> > > At present it is impossible to change the qemu_arm64 defconfig to
> > > obtain a devicetree from the U-Boot build.
> > >
> > > This is necessary for FIT validation, for example, where the signature
> > > node must be compiled into U-Boot.
> > >
> > > A proposed change to QEMU to allow device tree additions has been
> > > blocked for several years. The only known workaround is to use QEMU's
> > > dumpdtb option, merge in the signature node manually, disable
> > > OF_HAS_PRIOR_STAGE and then start QEMU with special arguments. This is
> > > complicated enough that it is documented in U-Boot[1].
> >
> > This paragraph and then
> >
> > [snip]
> > > +       Note: this work-around is necessary since Linaro has blocked
> > > +       addition of a feature to support additions to the QEMU devicetree:
> >
> > This part of the help are overly antagonistic.
> >
> > [snip]
> > > diff --git a/dts/Kconfig b/dts/Kconfig
> > > index 2e88d210bb8..53f7e246a80 100644
> > > --- a/dts/Kconfig
> > > +++ b/dts/Kconfig
> > > @@ -205,8 +205,13 @@ config OF_HAS_PRIOR_STAGE
> > >         development purposes, but it is not recommended, and likely will not
> > >         even work, for production systems.
> > >
> > > -       Note: This option must be set in Kconfig and cannot be enabled or
> > > -       disabled in the board's defconfig file.
> > > +       Note: This option can be disabled for QEMU usiing QEMU_MANUAL_DTB thus
> > > +       allowing QEMU to support FIT validation, where the devicetree must
> > > +       include a public key.
> > > +
> > > +       See also this for context:
> > > +
> > > +       https://patchwork.kernel.org/project/qemu-devel/patch/20210926183410.256484-1-sjg@chromium.org/#24481799
> >
> > And we don't need more wording here. The QEMU_MANUAL_DTB option itself
> > is enough.
> 
> I believe what I said is true, Ilias' comments to the contrary
> notwithstanding. If I were trying to be antagonistic I would perhaps
> express my views in a different manner.
> 
> Perhaps we should discuss whether Linaro should have maintainship on
> these important projects? U-Boot depends on QEMU and for it to block
> that patch is really not that good. It just makes things hard for
> open-source firmware.

If you wish to argue that Linaro as an organization has undue influence
in the open source community, this project is not the right forum to
raise that concern on. You should submit an op-ed to any of the
OSS-focused new sites or something perhaps, I don't know. Because QEMU
is a member of the Software Freedom Conservancy project, which is also
where I am trying to steer us to, and they take the idea of keeping
community projects as community run seriously.

-- 
Tom
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