linux-kernel - Re: [PATCH 1/2] leds: ncp5623: Add device tree binding documentation

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Date:	Tue, 21 Jun 2016 17:28:02 +0200
From:	Jacek Anaszewski <j.anaszewski@...sung.com>
To:	Florian Vaussard <florian.vaussard@...il.com>
Cc:	devicetree@...r.kernel.org, Richard Purdie <rpurdie@...ys.net>,
	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
	Florian Vaussard <florian.vaussard@...g-vd.ch>
Subject: Re: [PATCH 1/2] leds: ncp5623: Add device tree binding documentation

Hi Florian,

Thanks for the patch. I have two remarks below.

On 06/21/2016 09:29 AM, Florian Vaussard wrote:
> Add device tree binding documentation for On Semiconductor NCP5623 I2C
> LED driver. The driver can independently control the PWM of the 3
> channels with 32 levels of intensity.
>
> The current delivered by the current source can be controlled using the
> led-max-microamp property. In order to control this value, it is also
> necessary to know the current on the Iref pin, hence the
> onnn,led-iref-microamp property. It is usually set using an external
> bias resistor, following Iref = Vref/Rbias with Vref=0.6V.
>
> Signed-off-by: Florian Vaussard <florian.vaussard@...g-vd.ch>
> ---
>   .../devicetree/bindings/leds/leds-ncp5623.txt      | 44 ++++++++++++++++++++++
>   1 file changed, 44 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/leds/leds-ncp5623.txt
>
> diff --git a/Documentation/devicetree/bindings/leds/leds-ncp5623.txt b/Documentation/devicetree/bindings/leds/leds-ncp5623.txt
> new file mode 100644
> index 0000000..0dc8345
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/leds-ncp5623.txt
> @@ -0,0 +1,44 @@
> +* ON Semiconductor - NCP5623 3-Channel LED Driver
> +
> +The NCP5623 is a 3-channel I2C LED driver. The brightness of each
> +channel can be independently set using 32 levels. Each LED is represented
> +as a sub-node of the device.
> +
> +Required properties:
> +  - compatible: Should be "onnn,ncp5623"
> +  - reg: I2C slave address (fixed to 0x38)
> +  - #address-cells: must be 1
> +  - #size-cells: must be 0
> +  - onnn,led-iref-microamp: Current on the Iref pin in microampere

I think that you don't need this property. Just provide the formula for
calculating led-max-microamp value, similarly as you're doing that in
the commit message.

> +  - led-max-microamp: Desired maximum current for each LED in microampere
> +                      (maximum 30000uA)

Please add instead of (maximum ...):

Valid values: min - max, step by N (rounded {up|down})

E.g.

Valid values: 10000 - 30000, step by 1000 (rounded down)

> +
> +LED sub-node properties:
> +  - reg : LED channel number (0..2)
> +  - For other LED properties see:
> +      Documentation/devicetree/bindings/leds/common.txt
> +
> +Example:
> +
> +led1: ncp5623@38 {
> +	#address-cells = <1>;
> +	#size-cells = <0>;
> +	compatible = "onnn,ncp5623";
> +	reg = <0x38>;
> +
> +	led1_r@0 {
> +		label = "ncp:power:red";
> +		reg = <0>;
> +		linux,default-trigger = "default-on";
> +	};
> +
> +	led1_b@1 {
> +		label = "ncp:power:blue";
> +		reg = <1>;
> +	};
> +
> +	led1_g@2 {
> +		label = "ncp:power:green";
> +		reg = <2>;
> +	};
> +};
>


-- 
Best regards,
Jacek Anaszewski