Date: Mon, 5 Feb 2024 08:50:56 +0100
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Simon Glass <sjg@...omium.org>
Cc: Rob Herring <robh@...nel.org>, devicetree@...r.kernel.org,
 linux-mtd@...ts.infradead.org, Tom Rini <trini@...sulko.com>, Michael Walle
 <mwalle@...nel.org>, U-Boot Mailing List <u-boot@...ts.denx.de>, Conor
 Dooley <conor+dt@...nel.org>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@...aro.org>, Pratyush Yadav <ptyadav@...zon.de>,
 Rafał Miłecki <rafal@...ecki.pl>, Richard Weinberger
 <richard@....at>, Vignesh Raghavendra <vigneshr@...com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 1/3] dt-bindings: mtd: partitions: Add binman
 compatible

Hi Simon,

sjg@...omium.org wrote on Sun, 4 Feb 2024 05:07:38 -0700:

> Hi Rob,
> 
> On Wed, 17 Jan 2024 at 08:56, Rob Herring <robh@...nel.org> wrote:
> >
> > On Thu, Jan 4, 2024 at 3:54 PM Simon Glass <sjg@...omium.org> wrote:  
> > >
> > > Hi Rob,
> > >
> > > On Thu, Dec 14, 2023 at 2:09 PM Simon Glass <sjg@...omium.org> wrote:  
> > > >
> > > > Hi Rob,
> > > >
> > > > On Thu, 14 Dec 2023 at 10:27, Rob Herring <robh@...nel.org> wrote:  
> > > > >
> > > > > On Fri, Dec 08, 2023 at 03:58:10PM -0700, Simon Glass wrote:  
> > > > > > Hi Rob,
> > > > > >
> > > > > > On Fri, 8 Dec 2023 at 14:56, Rob Herring <robh@...nel.org> wrote:  
> > > > > > >
> > > > > > > On Fri, Dec 8, 2023 at 11:47 AM Simon Glass <sjg@...omium.org> wrote:  
> > > > > > > >
> > > > > > > > Hi Rob,
> > > > > > > >
> > > > > > > > On Fri, 8 Dec 2023 at 08:00, Rob Herring <robh@...nel.org> wrote:  
> > > > > > > > >
> > > > > > > > > On Thu, Nov 16, 2023 at 10:28:50AM -0700, Simon Glass wrote:  
> > > > > > > > > > Add a compatible string for binman, so we can extend fixed-partitions
> > > > > > > > > > in various ways.
> > > > > > > > > >
> > > > > > > > > > Signed-off-by: Simon Glass <sjg@...omium.org>
> > > > > > > > > > ---
> > > > > > > > > >
> > > > > > > > > > (no changes since v5)
> > > > > > > > > >
> > > > > > > > > > Changes in v5:
> > > > > > > > > > - Add #address/size-cells and parternProperties
> > > > > > > > > > - Drop $ref to fixed-partitions.yaml
> > > > > > > > > > - Drop 'select: false'
> > > > > > > > > >
> > > > > > > > > > Changes in v4:
> > > > > > > > > > - Change subject line
> > > > > > > > > >
> > > > > > > > > > Changes in v3:
> > > > > > > > > > - Drop fixed-partition additional compatible string
> > > > > > > > > > - Drop fixed-partitions from the example
> > > > > > > > > > - Mention use of compatible instead of label
> > > > > > > > > >
> > > > > > > > > > Changes in v2:
> > > > > > > > > > - Drop mention of 'enhanced features' in fixed-partitions.yaml
> > > > > > > > > > - Mention Binman input and output properties
> > > > > > > > > > - Use plain partition@xxx for the node name
> > > > > > > > > >
> > > > > > > > > >  .../bindings/mtd/partitions/binman.yaml       | 68 +++++++++++++++++++
> > > > > > > > > >  .../bindings/mtd/partitions/partitions.yaml   |  1 +
> > > > > > > > > >  MAINTAINERS                                   |  5 ++
> > > > > > > > > >  3 files changed, 74 insertions(+)
> > > > > > > > > >  create mode 100644 Documentation/devicetree/bindings/mtd/partitions/binman.yaml
> > > > > > > > > >
> > > > > > > > > > diff --git a/Documentation/devicetree/bindings/mtd/partitions/binman.yaml b/Documentation/devicetree/bindings/mtd/partitions/binman.yaml
> > > > > > > > > > new file mode 100644
> > > > > > > > > > index 000000000000..329217550a98
> > > > > > > > > > --- /dev/null
> > > > > > > > > > +++ b/Documentation/devicetree/bindings/mtd/partitions/binman.yaml
> > > > > > > > > > @@ -0,0 +1,68 @@
> > > > > > > > > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > > > > > > > > +# Copyright 2023 Google LLC
> > > > > > > > > > +
> > > > > > > > > > +%YAML 1.2
> > > > > > > > > > +---
> > > > > > > > > > +$id: http://devicetree.org/schemas/mtd/partitions/binman.yaml#
> > > > > > > > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > > > > > > > +
> > > > > > > > > > +title: Binman firmware layout
> > > > > > > > > > +
> > > > > > > > > > +maintainers:
> > > > > > > > > > +  - Simon Glass <sjg@...omium.org>
> > > > > > > > > > +
> > > > > > > > > > +description: |
> > > > > > > > > > +  The binman node provides a layout for firmware, used when packaging firmware
> > > > > > > > > > +  from multiple projects. It is based on fixed-partitions, with some
> > > > > > > > > > +  extensions, but uses 'compatible' to indicate the contents of the node, to
> > > > > > > > > > +  avoid perturbing or confusing existing installations which use 'label' for a
> > > > > > > > > > +  particular purpose.
> > > > > > > > > > +
> > > > > > > > > > +  Binman supports properties used as inputs to the firmware-packaging process,
> > > > > > > > > > +  such as those which control alignment of partitions. This binding addresses
> > > > > > > > > > +  these 'input' properties. For example, it is common for the 'reg' property
> > > > > > > > > > +  (an 'output' property) to be set by Binman, based on the alignment requested
> > > > > > > > > > +  in the input.
> > > > > > > > > > +
> > > > > > > > > > +  Once processing is complete, input properties have mostly served their
> > > > > > > > > > +  purpose, at least until the firmware is repacked later, e.g. due to a
> > > > > > > > > > +  firmware update. The 'fixed-partitions' binding should provide enough
> > > > > > > > > > +  information to read the firmware at runtime, including decompression if
> > > > > > > > > > +  needed.  
> > > > > > > > >
> > > > > > > > > How is this going to work exactly? binman reads these nodes and then
> > > > > > > > > writes out 'fixed-partitions' nodes. But then you've lost the binman
> > > > > > > > > specifc parts needed for repacking.  
> > > > > > > >
> > > > > > > > No, they are the same node. I do want the extra information to stick
> > > > > > > > around. So long as it is compatible with fixed-partition as well, this
> > > > > > > > should work OK.  
> > > > > > >
> > > > > > > How can it be both? The partitions node compatible can be either
> > > > > > > 'fixed-partitions' or 'binman'.  
> > > > > >
> > > > > > Can we not allow it to be both? I have tried to adjust things in
> > > > > > response to feedback but perhaps the feedback was leading me down the
> > > > > > wrong path?  
> > > > >
> > > > > Sure, but then the schema has to and that means extending
> > > > > fixed-partitions.  
> > > >
> > > > Can we cross that bridge later? There might be resistance to it. I'm
> > > > not sure. For now, perhaps just a binman compatible works well enough
> > > > to make progress.  
> > >
> > > Is there any way to make progress on this? I would like to have
> > > software which doesn't understand the binman compatible to at least be
> > > able to understand the fixed-partition compatible. Is that acceptable?  
> >
> > There's only 2 ways that it can work. Either binman writes out
> > fixed-partition nodes dropping/replacing anything only defined for
> > binman or fixed-partition is extended to include what binman needs.  
> 
> OK, then I suppose the best way is to add a new binman compatible, as
> is done with this v6 series. People then need to choose it instead of
> fixed-partition.

I'm sorry this is not at all what Rob suggested, or did I totally
misunderstand his answer?

In both cases the solution is to generate a "fixed-partition" node. Now
up to you to decide whether binman should adapt the output to the
current schema, or if the current schema should be extended to
understand all binman's output.

At least that is my understanding and also what I kind of agree with.

Thanks,
Miquèl

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