linux-kernel - Re: [PATCH v2 1/3] dt-bindings: media: imx258: Add bindings for IMX258 sensor

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Date:   Wed, 23 Sep 2020 17:06:27 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        devicetree@...r.kernel.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] dt-bindings: media: imx258: Add bindings for
 IMX258 sensor

On Tue, 22 Sep 2020 at 21:23, Rob Herring <robh@...nel.org> wrote:
>
> > > If this is the only config, why does it need to be in DT?
> >
> > The sensor is capable of two settings: two lanes (1 and 2) and four
> > lanes described above.  However Linux driver requires the latter (four
> > lanes, 1+2+3+4).
> >
> > If I were to describe the bindings for HW, someone would really be
> > confused and try to use two lanes setup, which won't work. Driver won't
> > allow it.
>
> If someone has h/w with only 2 lanes connected, then they have to go
> add support to the driver whether we've documented 2 lanes in the
> binding or not.
>
> > I understand that bindings document the HW and describe its interface
> > but do we really want to put "theoretical" bindings which cannot be used
> > in practice with Linux kernel?
> >
> > If yes, how to nicely document this that only one setting is currently
> > working?
>
> You don't, at least in the binding. That's a driver issue. Bindings
> are separate. They are stored in the kernel tree for convenience, not
> because they are part of the kernel.

Mhmm... okay. I already sent v3 for this with fixed four lanes so I
will re-spin with 2 or 4 lanes setup.

Thanks for the review!

Best regards,
Krzysztof