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Date:   Tue, 8 Sep 2020 12:33:41 +0300
From:   Sakari Ailus <sakari.ailus@iki.fi>
To:     Sowjanya Komatineni <skomatineni@nvidia.com>
Cc:     Jacopo Mondi <jacopo@jmondi.org>, thierry.reding@gmail.com,
        jonathanh@nvidia.com, hverkuil@xs4all.nl,
        jacopo+renesas@jmondi.org, luca@lucaceresoli.net,
        leonl@leopardimaging.com, robh+dt@kernel.org, lgirdwood@gmail.com,
        broonie@kernel.org, linux-media@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 2/3] dt-bindings: media: imx274: Add optional input
 clock and supplies
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On Thu, Sep 03, 2020 at 09:40:57AM -0700, Sowjanya Komatineni wrote:
> 
> On 9/3/20 9:35 AM, Jacopo Mondi wrote:
> > Hi Sowjanya,
> > 
> > On Thu, Sep 03, 2020 at 09:05:27AM -0700, Sowjanya Komatineni wrote:
> > > On 9/3/20 5:55 AM, Jacopo Mondi wrote:
> > > > Hello Sowjanya,
> > > > 
> > > > On Tue, Sep 01, 2020 at 07:04:37PM -0700, Sowjanya Komatineni wrote:
> > > > > This patch adds IMX274 optional external clock input and voltage
> > > > > supplies to device tree bindings.
> > > > > 
> > > > > Reviewed-by: Luca Ceresoli <luca@lucaceresoli.net>
> > > > > Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
> > > > > ---
> > > > >    .../devicetree/bindings/media/i2c/sony,imx274.yaml  | 21 +++++++++++++++++++++
> > > > >    1 file changed, 21 insertions(+)
> > > > > 
> > > > > diff --git a/Documentation/devicetree/bindings/media/i2c/sony,imx274.yaml b/Documentation/devicetree/bindings/media/i2c/sony,imx274.yaml
> > > > > index 7ae47a6..57e7176 100644
> > > > > --- a/Documentation/devicetree/bindings/media/i2c/sony,imx274.yaml
> > > > > +++ b/Documentation/devicetree/bindings/media/i2c/sony,imx274.yaml
> > > > > @@ -25,6 +25,27 @@ properties:
> > > > >      reset-gpios:
> > > > >        maxItems: 1
> > > > > 
> > > > I just sent an update to my json-schema conversion of this bindings
> > > > document (not yet on patchwork, sorry) and Sakari pointed me to the
> > > > fact in between my v2 and my v4 this patch from you went in:
> > > > 4ea3273d24b ("dt-bindings: media: imx274: Add optional input clock and supplies")
> > > > 
> > > > I should probably now update my bindings conversion patch, basically
> > > > taking in what you've done here, but I would have one question.
> > > > 
> > > > > +  clocks:
> > > > > +    maxItems: 1
> > > > > +    description: Reference to the sensor input clock
> > > > > +
> > > > > +  clock-names:
> > > > > +    maxItems: 1
> > > > > +    items:
> > > > > +      - const: inck
> > > > > +
> > > > > +  vana-supply:
> > > > > +    description:
> > > > > +      Analog voltage supply, 2.8 volts
> > > > > +
> > > > > +  vdig-supply:
> > > > > +    description:
> > > > > +      Digital IO voltage supply, 1.8 volts
> > > > > +
> > > > > +  vddl-supply:
> > > > > +    description:
> > > > > +      Digital core voltage supply, 1.2 volts
> > > > 4ea3273d24b introduced these regulators as VANA-supply, VDIG-supply
> > > > and VDDL-supply (please note the upper-case names). This version uses
> > > > lower-case ones instead. Is this intentional ? The driver currently
> > > > does not parse any of these if I'm not mistaken, but as the bindings
> > > > in textual form defines an ABI which should be preserved during the
> > > > conversion to json-schema, should these be kept in upper-case ?
> > > > 
> > > > Thanks
> > > >      j
> > > Yes, based on feedback lower case was recommended. So, changed to use
> > > lower-case names.
> > > 
> > > These properties were not used by driver currently and from my prior series
> > > only dt-binding got merged as? no feedback was received on it for all prior
> > > versions.
> > > 
> > > So, should be ok to change to lower-case as there properties are introduced
> > > now and driver update using these properties is under review
> > > 
> > Well, I see that patch went in v5.9-rc1, so it will be part of v5.9.
> > 
> > If the bindings update goes in in v5.10 (or whatever comes after v5.9)
> > then we have a problem, as the DTB created for v5.9 won't work anymore
> > on any later version, and that should not happen. Alternatively, a fix
> > for the next -rc release could be fast-tracked, but you would
> > need to synchronize with the dt maintainers for that and make a patch
> > for the existing .txt bindings file.
> > 
> > If the name change happens in the yaml file and one release is made
> > with the old names, then we're stuck with those forever and ever, if I
> > got the situation right.
> > 
> > Please check with the dt and media maintainers, or they can comment
> > here if they glance through these lines.
> > 
> > Thanks
> >    j
> 
> Hi Leon Luo,
> 
> I used upper case for regulator supply names in all prior 4 versions of
> IMX274 patch series as I see some other media i2c drivers doing it and
> dt-binding patch from v3 got merged in 5.9-rc1 which was using upper-case.
> 
> Later received feedback from Sakari requesting to use lower-case names so
> updated to use lower case name now in v5.
> 
> Not sure if we have timeline to squeeze in patch to change names to
> lower-case before they get into 5.10.
> 
> Can you please comment?

We can merge patches through the fixes branch if needed. That is not an
issue.

> 
> Sakari,
> 
> Can you also help understand why can't we keep upper case for regulator
> supplies?
> 
> I see some other media i2c drivers using upper case as well.

The vast majority of bindings use lower case, that's it, simply.

-- 
Regards,

Sakari Ailus