Re: [PATCH 1/5] media: dt-bindings: media: imx335: Add supply bindings

[Kieran Bingham <kieran.bingham@ideasonboard.com>]

Hi Rob, Krzysztof,

Quoting Kieran Bingham (2023-10-11 10:51:08)
> Quoting Rob Herring (2023-10-10 18:09:41)
> > On Tue, Oct 10, 2023 at 01:51:22AM +0100, Kieran Bingham wrote:
> > > Add the bindings for the supply references used on the IMX335.
> > > 
> > > Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> > > ---
> > >  .../bindings/media/i2c/sony,imx335.yaml          | 16 ++++++++++++++++
> > >  1 file changed, 16 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/media/i2c/sony,imx335.yaml b/Documentation/devicetree/bindings/media/i2c/sony,imx335.yaml
> > > index a167dcdb3a32..1863b5608a5c 100644
> > > --- a/Documentation/devicetree/bindings/media/i2c/sony,imx335.yaml
> > > +++ b/Documentation/devicetree/bindings/media/i2c/sony,imx335.yaml
> > > @@ -32,6 +32,15 @@ properties:
> > >      description: Clock frequency from 6 to 27 MHz, 37.125MHz, 74.25MHz
> > >      maxItems: 1
> > >  
> > > +  avdd-supply:
> > > +    description: Analog power supply (2.9V)
> > > +
> > > +  ovdd-supply:
> > > +    description: Interface power supply (1.8V)
> > > +
> > > +  dvdd-supply:
> > > +    description: Digital power supply (1.2V)
> > > +
> > >    reset-gpios:
> > >      description: Reference to the GPIO connected to the XCLR pin, if any.
> > >      maxItems: 1
> > > @@ -60,6 +69,9 @@ required:
> > >    - compatible
> > >    - reg
> > >    - clocks
> > > +  - avdd-supply
> > > +  - ovdd-supply
> > > +  - dvdd-supply
> > 
> > New required properties are an ABI break. That's fine only if you can 
> > explain no one is using this binding.
> 

No one is using this /in-kernel-tree/.

This could be because the original support for IMX335 was added with
ACPI devices in mind, but even for device-tree, that's not surprising as
cameras may often be described in overlays, unless embedded in specific
products.

I'm trying to revise this series for a v2. Could I get a decision from
the DT maintainers on which direction I should take this please?

Would you prefer supplies to be 'required' (if supplies should always be
required) - or should I leave this as optional as the binding has
previously been accepted?




> I made these required due to a previous review comment on another
> driver:
> 
> - https://lore.kernel.org/all/6e163f4d-061d-3c20-4c2e-44c74d529f10@linaro.org/
> 
> I hadn't thought about the ABI break though.
> 
> So to clarify (for me):
>  - New bindings should always add -supply's as required.
>  - Adding -supply to existing bindings should be optional.
> 
> I guess that leaves a mix of devices that either are required or may be
> optional - but perhaps that can't be helped if the bindings have already
> got in.
> 
> The IMX335 driver was added in 45d19b5fb9ae ("media: i2c: Add imx335
> camera sensor driver"), and the bindings in 932741d451a5 ("media:
> dt-bindings: media: Add bindings for imx335") by Martina, who looks to
> be an Intel employee - so I suspect this is used through ACPI so far and
> not device tree.
> 
> Danielle, get_maintainer tells me you are looking after this device -
> can you confirm this ?
> 
> --
> Kieran
> 
> 
> > 
> > >    - port
> > >  
> > >  additionalProperties: false
> > > @@ -79,6 +91,10 @@ examples:
> > >              assigned-clock-parents = <&imx335_clk_parent>;
> > >              assigned-clock-rates = <24000000>;
> > >  
> > > +            avdd-supply = <&camera_vdda_2v9>;
> > > +            ovdd-supply = <&camera_vddo_1v8>;
> > > +            dvdd-supply = <&camera_vddd_1v2>;
> > > +
> > >              port {
> > >                  imx335: endpoint {
> > >                      remote-endpoint = <&cam>;
> > > -- 
> > > 2.34.1
> > >