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Date:   Sat, 15 Oct 2022 08:54:20 +0300
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Rob Herring <robh@kernel.org>
Cc:     "Lad, Prabhakar" <prabhakar.csengg@gmail.com>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Hans Verkuil <hverkuil@xs4all.nl>,
        Shawn Tu <shawnx.tu@intel.com>,
        Jacopo Mondi <jacopo@jmondi.org>, linux-media@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-renesas-soc@vger.kernel.org,
        Biju Das <biju.das.jz@bp.renesas.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Subject: Re: [PATCH v2 1/5] media: dt-bindings: ov5645: Convert OV5645
 binding to a schema
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Hi Rob,

On Fri, Oct 14, 2022 at 04:40:29PM -0500, Rob Herring wrote:
> On Fri, Oct 14, 2022 at 10:27:53PM +0100, Lad, Prabhakar wrote:
> > On Fri, Oct 14, 2022 at 10:05 PM Rob Herring <robh+dt@kernel.org> wrote:
> > > On Fri, Oct 14, 2022 at 1:35 PM Prabhakar <prabhakar.csengg@gmail.com> wrote:
> > > >
> > > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > > >
> > > > Convert the simple OV5645 Device Tree binding to json-schema.
> > > >
> > > > The previous binding marked the below properties as required which was a
> > > > driver requirement and not the device requirement so just drop them from
> > > > the required list during the conversion.
> > > > - clock-frequency
> > > > - enable-gpios
> > > > - reset-gpios
> > > >
> > > > Also drop the "clock-names" property as we have a single clock source for
> > > > the sensor and the driver has been updated to drop the clk referencing by
> > > > name.
> > >
> > > Driver requirements are the ABI!
> > >
> > > This breaks a kernel without the driver change and a DTB that has
> > > dropped the properties.
> > >
> > I already have a patch for the driver [0] which I missed to include
> > along with the series.
> 
> You completely miss the point. Read the first sentence again. Changing 
> driver requirements changes the ABI.
> 
> This breaks the ABI. The driver patch does not help that.

I'm not following you here. If the DT binding makes a mandatory property
optional, it doesn't break any existing platform. The only thing that
would not work is a new DT that doesn't contain the now optional
property combined with an older driver that makes it required. That's
not a regression, as it would be a *new* DT.

> > > Also, with 'clock-names' dropped, you've just introduced a bunch of
> > > warnings on other people's platforms. Are you going to 'fix' all of
> > > them?
> > >
> > Yes I will fix them, once the patch driver patch [0] is merged in.
> 
> Why? You are just making extra work. We have enough warnings as-is to 
> fix.

I agree that a DT binding change should patch all in-tree DTS to avoid
introducing new warnings.

-- 
Regards,

Laurent Pinchart