Re: [PATCH v1 2/2] dt: bindings: lp50xx: Add max-brightness as in leds-pwm

[Astrid Rost]

On 6/29/23 19:59, Rob Herring wrote:
> On Thu, Jun 29, 2023 at 03:47:22PM +0200, Astrid Rost wrote:
> > Add max-brightness in order to reduce the current on the connected LEDs.
> > Normally, the maximum brightness is determined by the hardware, and this
> > property is not required. This property is used to set a software limit.
> > It could happen that an LED is made so bright that it gets damaged or
> > causes damage due to restrictions in a specific system, such as mounting
> > conditions.
> >
> > Signed-off-by: Astrid Rost <astrid.rost@xxxxxxxx>
> > ---
> >   Documentation/devicetree/bindings/leds/leds-lp50xx.yaml | 9 +++++++++
> >   1 file changed, 9 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/leds/leds-lp50xx.yaml b/Documentation/devicetree/bindings/leds/leds-lp50xx.yaml
> > index 402c25424525..6a1425969cb4 100644
> > --- a/Documentation/devicetree/bindings/leds/leds-lp50xx.yaml
> > +++ b/Documentation/devicetree/bindings/leds/leds-lp50xx.yaml
> > @@ -73,6 +73,15 @@ patternProperties:
> >         '#size-cells':
> >           const: 0
> >   
> > +      max-brightness:
> > +        description:
> > +          Normally, the maximum brightness is determined by the hardware, and
> > +          this property is not required. This property is used to set a software
> > +          limit. It could happen that an LED is made so bright that it gets
> > +          damaged or causes damage due to restrictions in a specific system,
> > +          such as mounting conditions.
> > +        $ref: /schemas/types.yaml#definitions/uint32
>
> We already have led-max-microamp. If this h/w works by controlling the
> current, then that is what you should use. "max-brightness" makes more
> sense for PWM based control.

Yes, I looked into this. This LED controller TI-LP5024 has only one flag 
as max current option, which allows to set between 35 mA and the default 
value 25.5 mA. This is not enough for our application.

> If you do end up keeping this, it belongs in the 'led' nodes not the
> controller as brightness is a property of the LED, not the LED
> driver(controller). And it should be in common schema rather than
> defining the type yet again.

I will look moving it into the the LED generic bindings as Andy 
suggested. max_brightness is already there and handled correctly. It is 
just a matter of reading it from the devicetree.

> Rob