[RFC PATCH 0/5] Allow for removal of DT nodes and properties

[Simon Glass]

Hi Peter,

On Mon, 28 Aug 2023 at 14:29, Peter Robinson <pbrobinson at gmail.com> wrote:
>
> On Mon, Aug 28, 2023 at 6:54 PM Simon Glass <sjg at chromium.org> wrote:
> >
> > Hi Peter,
> >
> > On Mon, 28 Aug 2023 at 10:37, Peter Robinson <pbrobinson at gmail.com> wrote:
> > >
> > > On Mon, Aug 28, 2023 at 5:20 PM Simon Glass <sjg at chromium.org> wrote:
> > > >
> > > > Hi,
> > > >
> > > > On Sat, 26 Aug 2023 at 03:07, Sughosh Ganu <sughosh.ganu at linaro.org> wrote:
> > > > >
> > > > >
> > > > > Provide a way for removing certain devicetree nodes and/or properties
> > > > > from the devicetree. This is needed to purge certain nodes and
> > > > > properties which may be relevant only in U-Boot. Such nodes and
> > > > > properties are then removed from the devicetree before it is passed to
> > > > > the kernel. This ensures that the devicetree passed to the OS does not
> > > > > contain any non-compliant nodes and properties.
> > > > >
> > > > > The removal of the nodes and properties is being done through an
> > > > > EVT_FT_FIXUP handler. I am not sure if the removal code needs to be
> > > > > behind any Kconfig symbol.
> > > > >
> > > > > I have only build tested this on sandbox, and tested on qemu arm64
> > > > > virt platform. This being a RFC, I have not put this through a CI run.
> > > > >
> > > > > Sughosh Ganu (5):
> > > > >   dt: Provide a way to remove non-compliant nodes and properties
> > > > >   fwu: Add the fwu-mdata node for removal from devicetree
> > > > >   capsule: Add the capsule-key property for removal from devicetree
> > > > >   bootefi: Call the EVT_FT_FIXUP event handler
> > > > >   doc: Add a document for non-compliant DT node/property removal
> > > > >
> > > > >  cmd/bootefi.c                                 | 18 +++++
> > > > >  .../devicetree/dt_non_compliant_purge.rst     | 64 ++++++++++++++++
> > > > >  drivers/fwu-mdata/fwu-mdata-uclass.c          |  5 ++
> > > > >  include/dt-structs.h                          | 11 +++
> > > > >  lib/Makefile                                  |  1 +
> > > > >  lib/dt_purge.c                                | 73 +++++++++++++++++++
> > > > >  lib/efi_loader/efi_capsule.c                  |  7 ++
> > > > >  7 files changed, 179 insertions(+)
> > > > >  create mode 100644 doc/develop/devicetree/dt_non_compliant_purge.rst
> > > > >  create mode 100644 lib/dt_purge.c
> > > >
> > > > What is the point of removing them? Instead, we should make sure that
> > > > we upstream the bindings and encourage SoC vendors to sync them. If we
> > > > remove them, no one will bother and U-Boot just becomes a dumping
> > > > ground.
> > >
> > > Well things like the binman entries in DT are U-Boot specific and not
> > > useful for HW related descriptions or for Linux or another OS being
> > > able to deal with HW so arguably we're already a dumping ground to
> > > some degree for not defining hardware.
> >
> > I have started the process to upstream the binman bindings.
>
> I don't think they should be in DT at all, they don't describe
> anything to do with hardware, or generally even the runtime of a
> device, they don't even describe the boot/runtime state of the
> firmware, they describe build time, so I don't see what that has to do
> with device tree? Can you explain that? To me those sorts of things
> should live in a build time style config file.

I beg to differ. Devicetree is more than just hardware and always has
been. See, for example the /chosen and /options nodes.

We need run-time configuration here, since we cannot know at build
time what we will be asked to do by a previous firmware phase.

>
> > Perhaps we should use the issue tracker[1] to follow progress on all
> > of this. We need to clean it up.
> >
> > >
> > > > Instead of this, how about working on bringing the DT validation into
> > > > U-Boot so we can see what state things are in?
> > > >
> > > > Please send the bindings for Linaro's recent series (which I suspect
> > > > are motivating this series) so we can start the process.
> >
> > Regards,
> > Simon
> >
> > [1] https://source.denx.de/u-boot/u-boot/-/issues

Regards,
Simon