Date:   Mon, 14 Feb 2022 19:10:58 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Cc:     Rob Herring <robh@...nel.org>, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linux-phy@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-staging@...ts.linux.dev, Yong Deng <yong.deng@...ewell.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Helen Koike <helen.koike@...labora.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v2 61/66] dt-bindings: media: Add Allwinner A31 ISP
 bindings documentation

On Mon, Feb 14, 2022 at 05:28:50PM +0100, Paul Kocialkowski wrote:
> Hi,
> 
> On Fri 11 Feb 22, 22:52, Laurent Pinchart wrote:
> > Hi Rob,
> > 
> > On Fri, Feb 11, 2022 at 09:13:30AM -0600, Rob Herring wrote:
> > > On Mon, Feb 07, 2022 at 05:51:21PM +0200, Laurent Pinchart wrote:
> > > > On Sat, Feb 05, 2022 at 07:54:24PM +0100, Paul Kocialkowski wrote:
> > > > > This introduces YAML bindings documentation for the Allwinner A31 Image
> > > > > Signal Processor (ISP).
> > > > > 
> > > > > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>
> > > > > ---
> > > > >  .../media/allwinner,sun6i-a31-isp.yaml        | 117 ++++++++++++++++++
> > > > >  1 file changed, 117 insertions(+)
> > > > >  create mode 100644 Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml
> > > > > 
> > > > > diff --git a/Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml b/Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml
> > > > > new file mode 100644
> > > > > index 000000000000..2d87022c43ce
> > > > > --- /dev/null
> > > > > +++ b/Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml
> > > > > @@ -0,0 +1,117 @@
> > > > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > > > +%YAML 1.2
> > > > > +---
> > > > > +$id: http://devicetree.org/schemas/media/allwinner,sun6i-a31-isp.yaml#
> > > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > > +
> > > > > +title: Allwinner A31 Image Signal Processor Driver (ISP) Device Tree Bindings
> > > > > +
> > > > > +maintainers:
> > > > > +  - Paul Kocialkowski <paul.kocialkowski@...tlin.com>
> > > > > +
> > > > > +properties:
> > > > > +  compatible:
> > > > > +    enum:
> > > > > +      - allwinner,sun6i-a31-isp
> > > > > +      - allwinner,sun8i-v3s-isp
> > > > > +
> > > > > +  reg:
> > > > > +    maxItems: 1
> > > > > +
> > > > > +  interrupts:
> > > > > +    maxItems: 1
> > > > > +
> > > > > +  clocks:
> > > > > +    items:
> > > > > +      - description: Bus Clock
> > > > > +      - description: Module Clock
> > > > > +      - description: DRAM Clock
> > > > 
> > > > That's interesting, does the ISP have a dedicated DRAM ?
> > > > 
> > > > > +
> > > > > +  clock-names:
> > > > > +    items:
> > > > > +      - const: bus
> > > > > +      - const: mod
> > > > > +      - const: ram
> > > > > +
> > > > > +  resets:
> > > > > +    maxItems: 1
> > > > > +
> > > > > +  ports:
> > > > > +    $ref: /schemas/graph.yaml#/properties/ports
> > > > > +
> > > > > +    properties:
> > > > > +      port@0:
> > > > > +        $ref: /schemas/graph.yaml#/$defs/port-base
> > > > > +        description: CSI0 input port
> > > > > +
> > > > > +        properties:
> > > > > +          reg:
> > > > > +            const: 0
> > > > > +
> > > > > +          endpoint:
> > > > > +            $ref: video-interfaces.yaml#
> > > > > +            unevaluatedProperties: false
> > > > 
> > > > If no other property than remote-endpoint are allowed, I'd write
> > > > 
> > > >           endpoint:
> > > >             $ref: video-interfaces.yaml#
> > > > 	    remote-endpoint: true
> > > 
> > > You just mixed a node and a property...
> > 
> > Yes, I meant
> > 
> >            endpoint:
> >              $ref: video-interfaces.yaml#
> >              properties:
> >                remote-endpoint: true
> > 
> > and actually add
> > 
> >              additionalProperties: false
> > 
> > > 'remote-endpoint' is always allowed, so need to put it here and every 
> > > other user. So 'unevaluatedProperties' is correct. But it would be good 
> > > to define what properties from video-interfaces.yaml are used here.
> > 
> > I've been looking at this recently. The usual pattern is to write
> > 
> >     endpoint:
> >       $ref: video-interfaces.yaml#
> >       unevaluatedProperties: false
> >       properties:
> >         hsync-polarity: true
> >         vsync-polarity: true
> > 
> > to express that the hsync-polarity and vsync-polarity properties are
> > used. However, this will still validate fine if, for instance,
> > data-lanes was specified in the device tree. Shouldn't we use
> > additionalProperties instead of unevaluatedProperties here ? If so,
> > specifying remote-endpoint: true seems needed.
> 
> My understanding is that unevaluatedProperties well allow all properties
> defined in the included video-interfaces.yaml ref but reject others
> while additionalProperties will reject any unspecified local property,
> even if it is declared in the ref.
> 
> In any case with the ISP maybe we don't even want to take the ref from
> video-interfaces.yaml since we are dealing with an internal fifo between
> two devices. Maybe it would be more appropriate to ref
> /schemas/graph.yaml#/$defs/endpoint-base, which already defines
> remote-endpoint too.
> 
> What do you think?

Yes, if no additional property are needed, you can replace port-base
with port, it will simplify the bindings.

-- 
Regards,

Laurent Pinchart

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