linux-kernel - Re: [PATCH 4/4] devicetree: Add led-backlight binding

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Message-ID: <20190702095849.fxlmiqcioihsi3zk@holly.lan>
Date:   Tue, 2 Jul 2019 10:58:49 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Jean-Jacques Hiblot <jjhiblot@...com>
Cc:     jacek.anaszewski@...il.com, pavel@....cz, robh+dt@...nel.org,
        mark.rutland@....com, lee.jones@...aro.org, jingoohan1@...il.com,
        dmurphy@...com, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        tomi.valkeinen@...com, devicetree@...r.kernel.org
Subject: Re: [PATCH 4/4] devicetree: Add led-backlight binding

On Mon, Jul 01, 2019 at 05:14:23PM +0200, Jean-Jacques Hiblot wrote:
> From: Tomi Valkeinen <tomi.valkeinen@...com>
> 
> Add DT binding for led-backlight.

I think the patchset is in the wrong order; the DT bindings
documentation should appear *before* the binding is
implemented (amoung other things this prevent transient checkpatch
warnings as the patchset is applied).


> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...com>
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@...com>
> Cc: devicetree@...r.kernel.org
> ---
>  .../video/backlight/led-backlight.txt         | 39 +++++++++++++++++++
>  1 file changed, 39 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/video/backlight/led-backlight.txt
> 
> diff --git a/Documentation/devicetree/bindings/video/backlight/led-backlight.txt b/Documentation/devicetree/bindings/video/backlight/led-backlight.txt
> new file mode 100644
> index 000000000000..216cd52d624a
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/video/backlight/led-backlight.txt
> @@ -0,0 +1,39 @@
> +led-backlight bindings
> +
> +The node of the backlight driver IS the node of the LED.
> +
> +Required properties:
> +  - compatible: "led-backlight"
> +  - brightness-levels: Array of distinct LED brightness levels. These
> +      are in the range from 0 to 255, passed to the LED class driver.
> +  - default-brightness-level: the default brightness level (index into the
> +      array defined by the "brightness-levels" property)

I think brightness-levels and default-brightness-level could be
optional properties since a default 1:1 mapping seems reasonable given
how constrained the LED brightness values are.


Daniel.


> +
> +Optional properties:
> +  - power-supply: regulator for supply voltage
> +  - enable-gpios: contains a single GPIO specifier for the GPIO which enables
> +                  and disables the backlight (see GPIO binding[0])
> +
> +[0]: Documentation/devicetree/bindings/gpio/gpio.txt
> +
> +Example:
> +
> +led_ctrl {
> +	red_led@1 {
> +	        label = "red";
> +		reg = <1>;
> +	}
> +
> +	backlight_led@2 {
> +		function = LED_FUNCTION_BACKLIGHT;
> +		reg = <2>;
> +
> +		compatible = "led-backlight";
> +
> +		brightness-levels = <0 4 8 16 32 64 128 255>;
> +		default-brightness-level = <6>;
> +
> +		power-supply = <&vdd_bl_reg>;
> +		enable-gpios = <&gpio 58 0>;
> +	};
> +};
> -- 
> 2.17.1
>