Re: [PATCH v2 1/2] dt-bindings: regulator: rpi-panel-v2: Add required vcc-supply property

[Shashank Maurya <shashank.maurya@oss.qualcomm.com>]

On Mon, Sep 07, 2026 at 06:10:36PM +0100, Conor Dooley wrote:
> On Mon, Sep 07, 2026 at 02:24:09PM +0100, Dave Stevenson wrote:
> > Hi Shashank
> > 
> > (Apologies for the earlier HTML version of this - I thought I had my
> > mail client under control)
> > 
> > On Mon, 7 Sept 2026 at 06:48, Shashank Maurya
> > <shashank.maurya@oss.qualcomm.com> wrote:
> > >
> > > Add a vcc-supply property to the Raspberry Pi 7" touchscreen panel V2
> > > regulator binding and mark it as required. The panel controller MCU
> > > needs an external power rail to be supplied before any I2C communication
> > > can take place.
> > >
> > > Signed-off-by: Shashank Maurya <shashank.maurya@oss.qualcomm.com>
> > > ---
> > >  .../regulator/raspberrypi,7inch-touchscreen-panel-regulator-v2.yaml  | 5 +++++
> > >  1 file changed, 5 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/regulator/raspberrypi,7inch-touchscreen-panel-regulator-v2.yaml b/Documentation/devicetree/bindings/regulator/raspberrypi,7inch-touchscreen-panel-regulator-v2.yaml
> > > index 37b9ed371b67..a6195e53be16 100644
> > > --- a/Documentation/devicetree/bindings/regulator/raspberrypi,7inch-touchscreen-panel-regulator-v2.yaml
> > > +++ b/Documentation/devicetree/bindings/regulator/raspberrypi,7inch-touchscreen-panel-regulator-v2.yaml
> > > @@ -35,6 +35,9 @@ properties:
> > >      const: 3
> > >      description: See ../../pwm/pwm.yaml for description of the cell formats.
> > >
> > > +  vcc-supply:
> > > +    description: Regulator supplying power to the panel controller.
> > > +
> > >  additionalProperties: false
> > >
> > >  required:
> > > @@ -43,6 +46,7 @@ required:
> > >    - gpio-controller
> > >    - "#gpio-cells"
> > >    - "#pwm-cells"
> > > +  - vcc-supply
> > 
> > Adding a new property as "required" breaks all existing users. Adding
> > it as optional would be reasonable.
> 
> It can be made required here, but never in the driver. If it's actually
> required that something turn this on before the device can be used,
> making it required is probably correct.

Thanks Dave for clarification. I also see one existing consumer of this 
regulator driver: arch/arm64/boot/dts/renesas/r8a779g3-sparrow-hawk-rpi-display-2.dtsi

So, adding required in bindings will fail for this user. 
Apologies, I didn't notice this earlier.

> 
> > 
> >   Dave
> > 
> > >
> > >  examples:
> > >    - |
> > > @@ -55,6 +59,7 @@ examples:
> > >          gpio-controller;
> > >          #gpio-cells = <2>;
> > >          #pwm-cells = <3>;
> > > +        vcc-supply = <&vcc_reg>;
> > >        };
> > >      };
> > >
> > >
> > > --
> > > 2.34.1
> > >
> > >