linux-kernel - Re: [PATCH v2 1/1] dt-bindings: backlight: mp3309c: remove two required properties

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Date:   Thu, 26 Oct 2023 15:57:40 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Flavio Suligoi <f.suligoi@...m.it>
Cc:     Lee Jones <lee@...nel.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Helge Deller <deller@....de>, Pavel Machek <pavel@....cz>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        dri-devel@...ts.freedesktop.org, linux-leds@...r.kernel.org,
        devicetree@...r.kernel.org, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] dt-bindings: backlight: mp3309c: remove two
 required properties

On Wed, Oct 25, 2023 at 05:50:57PM +0200, Flavio Suligoi wrote:
> The two properties:
> 
> - max-brightness
> - default brightness
> 
> are not really required, so they can be removed from the "required"
> section.
> The "max-brightness" is no longer used in the current version
> of the driver (it was used only in the first version).
> The "default-brightness", if omitted in the DT, is managed by the
> device driver, using a default value. This value depends on the dimming
> mode used:
> 
> - for the "analog mode", via I2C commands, this value is fixed by
>   hardware (=31)
> - while in case of pwm mode the default used is the last value of the
>   brightness-levels array.
> 
> Also the brightness-levels array is not required:
> 
> - in "analog mode", via I2C commands, the brightness-level array is
>   fixed by hardware (0..31).;
> - in pwm dimming mode, the driver uses a default array of 0..255 and
>   the "default-brightness" is the last one, which is "255"
> 

> NOTE: there are no compatibility problems with the previous version,
>       since the device driver has not yet been included in any kernel.
>       Only this dt-binding yaml file is already included in the
>       "for-backlight-next" branch of the "backlight" kernel repository.
>       No developer may have used it.

I'd argue
Fixes: 02c4e661658f ("dt-bindings: backlight: Add MPS MP3309C")
but that's up to Lee.
Acked-by: Conor Dooley <conor.dooley@...rochip.com>

Thanks,
Conor.

> 
> Other changes:
> 
> - improve the backlight working mode description, in the "description"
>   section
> - update the example, removing the "max-brightness" and introducing the
>   "brightess-levels" property
> 
> Signed-off-by: Flavio Suligoi <f.suligoi@...m.it>
> ---
>  .../bindings/leds/backlight/mps,mp3309c.yaml           | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/leds/backlight/mps,mp3309c.yaml b/Documentation/devicetree/bindings/leds/backlight/mps,mp3309c.yaml
> index 4191e33626f5..527a37368ed7 100644
> --- a/Documentation/devicetree/bindings/leds/backlight/mps,mp3309c.yaml
> +++ b/Documentation/devicetree/bindings/leds/backlight/mps,mp3309c.yaml
> @@ -14,8 +14,8 @@ description: |
>    programmable switching frequency to optimize efficiency.
>    It supports two different dimming modes:
>  
> -  - analog mode, via I2C commands (default)
> -  - PWM controlled mode.
> +  - analog mode, via I2C commands, as default mode (32 dimming levels)
> +  - PWM controlled mode (optional)
>  
>    The datasheet is available at:
>    https://www.monolithicpower.com/en/mp3309c.html
> @@ -50,8 +50,6 @@ properties:
>  required:
>    - compatible
>    - reg
> -  - max-brightness
> -  - default-brightness
>  
>  unevaluatedProperties: false
>  
> @@ -66,8 +64,8 @@ examples:
>              compatible = "mps,mp3309c";
>              reg = <0x17>;
>              pwms = <&pwm1 0 3333333 0>; /* 300 Hz --> (1/f) * 1*10^9 */
> -            max-brightness = <100>;
> -            default-brightness = <80>;
> +            brightness-levels = <0 4 8 16 32 64 128 255>;
> +            default-brightness = <6>;
>              mps,overvoltage-protection-microvolt = <24000000>;
>          };
>      };
> -- 
> 2.34.1
> 

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