Re: [PATCH 2/3] dt-bindings: mtd: Add Documentation for Airoha fixed-partitions

[Christian Marangi <ansuelsmth@xxxxxxxxx>]

On Wed, Sep 25, 2024 at 01:30:03PM +0200, Miquel Raynal wrote:
> Hi Christian,
> 
> ansuelsmth@xxxxxxxxx wrote on Wed, 25 Sep 2024 12:13:58 +0200:
> 
> > Add Documentation for Airoha fixed-partitions compatibles.
> > 
> > Airoha based SoC declare a dedicated partition at the end of the flash to
> > store calibration and device specific data, in addition to fixed
> > partitions.
> > 
> > The offset of this special partition is not well defined as a custom bad
> > block management driver is used that reserve space at the end of the flash.
> > 
> > This binding allows defining all fixed partitions and marking the last one
> > to detect the correct offset.
> > 
> > Signed-off-by: Christian Marangi <ansuelsmth@xxxxxxxxx>
> > ---
> >  .../partitions/airoha,fixed-partitions.yaml   | 80 +++++++++++++++++++
> >  .../bindings/mtd/partitions/partitions.yaml   |  1 +
> >  2 files changed, 81 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/mtd/partitions/airoha,fixed-partitions.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/mtd/partitions/airoha,fixed-partitions.yaml b/Documentation/devicetree/bindings/mtd/partitions/airoha,fixed-partitions.yaml
> > new file mode 100644
> > index 000000000000..a45df51065af
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/mtd/partitions/airoha,fixed-partitions.yaml
> > @@ -0,0 +1,80 @@
> > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/mtd/partitions/airoha,fixed-partitions.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Airoha SoC partitioning
> > +
> > +description: |
> > +  Airoha based SoC declare a dedicated partition at the end of the flash to
> > +  store calibration and device specific data, in addition to fixed partitions.
> > +
> > +  The offset of this special partition is not well defined as a custom bad block
> > +  management driver is used that reserve space at the end of the flash.
> > +
> > +  This binding allows defining all fixed partitions and marking the last one to
> > +  detect the correct offset from the new end of the flash.
> > +
> > +maintainers:
> > +  - Christian Marangi <ansuelsmth@xxxxxxxxx>
> > +
> > +select: false
> > +
> > +properties:
> > +  compatible:
> > +    const: airoha,fixed-partitions
> > +
> > +  "#address-cells":
> > +    enum: [ 1, 2 ]
> > +
> > +  "#size-cells":
> > +    enum: [ 1, 2 ]
> > +
> > +patternProperties:
> > +  "^partition@[0-9a-f]+$":
> > +    $ref: partition.yaml#
> > +    properties:
> > +      compatible:
> > +        const: airoha,dynamic-art
> > +    unevaluatedProperties: false
> > +
> > +required:
> > +  - "#address-cells"
> > +  - "#size-cells"
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    partitions {
> > +        compatible = "airoha,fixed-partitions";
> > +        #address-cells = <1>;
> > +        #size-cells = <1>;
> > +
> > +        partition@0 {
> > +          label = "bootloader";
> > +          reg = <0x00000000 0x00080000>;
> > +        };
> > +
> > +        partition@80000 {
> > +          label = "tclinux";
> > +          reg = <0x00080000 0x02800000>;
> > +        };
> > +
> > +        partition@2880000 {
> > +          label = "tclinux_slave";
> > +          reg = <0x02880000 0x02800000>;
> > +        };
> > +
> > +        partition@5080000 {
> > +          label = "rootfs_data";
> > +          reg = <0x5080000 0x00800000>;
> > +        };
> > +
> > +        partition@ffffffff {
> > +          compatible = "airoha,dynamic-art";
> > +          label = "art";
> > +          reg = <0xffffffff 0x00300000>;
> 
> I'm a little bit puzzled by this kind of information which is known to
> be wrong. As the partition offset and size must be dynamically
> calculated, this reg property (as well as the size parameter of the
> previous one) are notably wrong. I guess we are not fully constrained
> by the fixed-partitions schema here, so could we avoid the reg property
> in the airoha,dynamic-art partition? Maybe we also need a #define for a
> specific placeholder in the penultimate reg property too (for the size).
>

Maybe instead of reg we can use a property like size?

Can you better elaborate the suggestion about the #define?

Do you mean for case where the last partition might overlap
with the penultimate? Honestly in such case I would error hard, that
case happen when too much space is reserved and that is a
misconfiguration of the system (developer error)

-- 
	Ansuel