linux-kernel - Re: [PATCH] media: dt-bindings: media: renesas,csi2: Update data-lanes property

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Message-ID: <CA+V-a8t=f14QH=M8p8mufeJsqddwOn6XPqFma5TEbfQ7XdLBZA@mail.gmail.com>
Date:   Tue, 18 Jan 2022 09:11:42 +0000
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Jacopo Mondi <jacopo@...ndi.org>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Niklas Söderlund <niklas.soderlund@...natech.se>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Biju Das <biju.das.jz@...renesas.com>,
        linux-media <linux-media@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] media: dt-bindings: media: renesas,csi2: Update
 data-lanes property

Hi Jacopo,

Thank you for the review.

On Mon, Jan 17, 2022 at 8:11 AM Jacopo Mondi <jacopo@...ndi.org> wrote:
>
> Hello Prabhakar,
>
> On Thu, Jan 13, 2022 at 10:32:14AM +0000, Lad Prabhakar wrote:
> > CSI-2 (CSI4LNK0) on R-Car and RZ/G2 supports 4-lane mode which is already
> > handled by rcar-csi2.c driver. This patch updates the data-lanes property
> > to describe the same.
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > ---
> >  .../devicetree/bindings/media/renesas,csi2.yaml          | 9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/devicetree/bindings/media/renesas,csi2.yaml b/Documentation/devicetree/bindings/media/renesas,csi2.yaml
> > index e6a036721082..064a0a4c5737 100644
> > --- a/Documentation/devicetree/bindings/media/renesas,csi2.yaml
> > +++ b/Documentation/devicetree/bindings/media/renesas,csi2.yaml
> > @@ -67,7 +67,14 @@ properties:
> >                  maxItems: 1
> >
> >                data-lanes:
> > -                maxItems: 1
> > +                items:
> > +                  minItems: 1
> > +                  maxItems: 4
> > +                  items:
> > +                    - const: 1
> > +                    - const: 2
> > +                    - const: 3
> > +                    - const: 4
>
> Seeing "maxItems: 1" there confuses me too, as the property is an
> array of data-lanes, but I'm afraid your change does not what you
> intend as it would allow you to specify the number of data lanes as an
> integer rather than as an array.
>
Agreed, what do you think of the below instead?

            properties:
              data-lanes:
                minItems: 1
                maxItems: 4
                items:
                  maximum: 4

The above should handle all the possible mix and match of the lanes.

> I think it would probably be correct to set
>
>                 data-lanes: true
>
> (maybe maxItems: 1 is correct already)
>
> And restrict the number of valid combinations in the board DTS file
> with a construct like:
>
>     data-lanes:
>       oneOf:
>         - items:
>             - const: 1
>             - const: 2
>             - const: 3
>             - const: 4
>         - items:
>             - const: 1
>             - const: 2
>
I haven't come across dts files having such constraints is it allowed,
could you point me to a example.

Cheers,
Prabhakar