Re: [PATCH v3 6/6] dt-bindings: nvmem: add YAML schema for the ONIE tlv layout

[Rob Herring <robh@kernel.org>]

On Thu, Nov 10, 2022 at 06:43:34PM +0100, Miquel Raynal wrote:
> Hi Rob,
> 
> robh@kernel.org wrote on Thu, 10 Nov 2022 08:05:45 -0600:
> 
> > On Thu, Nov 10, 2022 at 09:50:34AM +0100, Miquel Raynal wrote:
> > > Hi Rob,
> > > 
> > > robh@kernel.org wrote on Wed, 9 Nov 2022 22:00:55 -0600:
> > >   
> > > > On Fri, Nov 04, 2022 at 05:38:33PM +0100, Miquel Raynal wrote:  
> > > > > Add a schema for the ONIE tlv NVMEM layout that can be found on any ONIE
> > > > > compatible networking device.
> > > > > 
> > > > > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > > > > ---
> > > > >  .../bindings/nvmem/layouts/nvmem-layout.yaml  |   1 +
> > > > >  .../nvmem/layouts/onie,tlv-layout.yaml        | 115 ++++++++++++++++++
> > > > >  2 files changed, 116 insertions(+)
> > > > >  create mode 100644 Documentation/devicetree/bindings/nvmem/layouts/onie,tlv-layout.yaml
> > > > > 
> > > > > diff --git a/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml b/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml
> > > > > index f64ea2fa362d..8512ee538c4c 100644
> > > > > --- a/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml
> > > > > +++ b/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml
> > > > > @@ -19,6 +19,7 @@ description: |
> > > > >  
> > > > >  oneOf:
> > > > >    - $ref: kontron,sl28-vpd.yaml
> > > > > +  - $ref: onie,tlv-layout.yaml
> > > > >  
> > > > >  properties:
> > > > >    compatible: true
> > > > > diff --git a/Documentation/devicetree/bindings/nvmem/layouts/onie,tlv-layout.yaml b/Documentation/devicetree/bindings/nvmem/layouts/onie,tlv-layout.yaml
> > > > > new file mode 100644
> > > > > index 000000000000..1d91277324ac
> > > > > --- /dev/null
> > > > > +++ b/Documentation/devicetree/bindings/nvmem/layouts/onie,tlv-layout.yaml
> > > > > @@ -0,0 +1,115 @@
> > > > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > > > +%YAML 1.2
> > > > > +---
> > > > > +$id: http://devicetree.org/schemas/nvmem/layouts/onie,tlv-layout.yaml#
> > > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > > +
> > > > > +title: NVMEM layout of the ONIE tlv table
> > > > > +
> > > > > +maintainers:
> > > > > +  - Miquel Raynal <miquel.raynal@bootlin.com>
> > > > > +
> > > > > +description:
> > > > > +  Modern networking hardware implementing the Open Compute Project ONIE
> > > > > +  infrastructure shall provide a non-volatile memory with a table whose the
> > > > > +  content is well specified and gives many information about the manufacturer
> > > > > +  (name, country of manufacture, etc) as well as device caracteristics (serial
> > > > > +  number, hardware version, mac addresses, etc). The underlaying device type
> > > > > +  (flash, EEPROM,...) is not specified. The exact location of each value is also
> > > > > +  dynamic and should be discovered at run time because it depends on the
> > > > > +  parameters the manufacturer decided to embed.
> > > > > +
> > > > > +properties:
> > > > > +  compatible:
> > > > > +    const: onie,tlv-layout
> > > > > +
> > > > > +  product-name: true    
> > > > 
> > > > This is a node? If so, you need:
> > > > 
> > > > type: object
> > > > additionalProperties: false  
> > > 
> > > I thought referencing a schema under a property would be enough?
> > > 
> > > Indeed in nvmem.yaml we create the property nvmem-layout and make it
> > > reference nvmem-layout.yaml. Then, in nvmem-layout.yaml:
> > > 
> > > 	 oneOf:
> > > 	  - $ref: kontron,sl28-vpd.yaml
> > > 	  - $ref: onie,tlv-layout.yaml
> > > 
> > > we reference the different layouts that may apply (very much like what
> > > you proposed to list the mtd partition parsers, if I got it right).
> > > 
> > > Isn't it enough?  
> > 
> > No. It is enough to allow the property, but nothing defines what it must 
> > be (a node) and what the node contains in the case of empty nodes. Try 
> > adding 'product-name = "foo";' and it won't warn.
> 
> There was a misunderstanding on my side. I thought your comment was
> about the nvmem-layout node. Actually you were commenting about all the
> sub-nodes defining nvmem-cells inside, so I'm fully aligned with your
> response.
> 
> However, if I understood it correctly, you basically said that:
> 
> 	property:
> 	  $ref: foo.yaml
> 
> is not the same as:
> 
> 	property:
> 	  type: object
> 	  $ref: foo.yaml
> 
> If that's the case, then should we consider dropping this patch (which
> you agreed with in the first place)?

From a json-schema standpoint, they may not be the same. You can't know 
without knowing what's in foo.yaml. They are the same only if foo.yaml 
contains 'type: object'. It does for us because the tools will add 
'type: object' to the top-level of every schema file.


properties:
  property:
    properties:
      foo: {}

These would all pass validation with the above:

property;
property = "bar";

More generally, json-schema's behavior is if a keyword doesn't apply for 
an instance, just silently ignore it. So while 'properties' keyword only 
makes sense on an object or maxItems on an array, json-schema doesn't 
care. The dtschema tools do a bit to counteract that.

Rob