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

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Date:   Thu, 29 Jun 2023 11:59:39 -0600
From:   Rob Herring <robh@...nel.org>
To:     Astrid Rost <astrid.rost@...s.com>
Cc:     Dan Murphy <dmurphy@...com>, Andrew Davis <afd@...com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Pavel Machek <pavel@....cz>, Lee Jones <lee@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, kernel@...s.com,
        linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/2] dt: bindings: lp50xx: Add max-brightness as in
 leds-pwm

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@...s.com>
> ---
>  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.

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.

Rob