linux-kernel - Re: [PATCH v2 1/2] leds: ncp5623: Add device tree binding documentation

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Message-id: <5770DF98.7010900@samsung.com>
Date:	Mon, 27 Jun 2016 10:11:04 +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>,
	Pavel Machek <pavel@....cz>, linux-leds@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Florian Vaussard <florian.vaussard@...g-vd.ch>
Subject: Re: [PATCH v2 1/2] leds: ncp5623: Add device tree binding documentation

Hi Florian,

On 06/27/2016 09:03 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 also be controlled. To
> do so, the led-max-microamp property is used by each LED sub-node. The
> maximum value is then found and used as a limit to compute the final
> intensity of the current source. If a LED happens to have a lower limit,
> the PWM is then used to limit the current to the requested value.
>
> In order to control the current source, 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      | 60 ++++++++++++++++++++++
>   1 file changed, 60 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..77dd7ad
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/leds-ncp5623.txt
> @@ -0,0 +1,60 @@
> +* 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. It depends
> +    on the value of the external bias resistor Rbias, following
> +    Iref = Vref / Rbias with Vref = 0.6V. This is used to set the intensity of
> +    the current that can be provided by the internal current source, based on
> +    the maximum current permitted by LED sub-nodes (see below), but no more than
> +    Imax = 2400 * Iref.
> +
> +LED sub-nodes
> +=============
> +
> +Required properties:
> +  - reg : LED channel number (0..2)
> +  - led-max-microamp: Maximum allowable current inside the LED in microampere.
> +    This property is used to limit the PWM ratio, based on the intensity of the
> +    internal current source (see above).
> +
> +Optional properties:
> +  - label: Used for naming LEDs

Instead of the above description use same reference to common led
bindings as below.

> +  - default-trigger: see Documentation/devicetree/bindings/leds/common.txt
> +
> +Example
> +=======
> +
> +led1: ncp5623@38 {
> +	#address-cells = <1>;
> +	#size-cells = <0>;
> +	compatible = "onnn,ncp5623";
> +	reg = <0x38>;
> +	onnn,led-iref-microamp = <10>;
> +
> +	led1r@0 {
> +		label = "ncp:power:red";
> +		linux,default-trigger = "default-on";
> +		reg = <0>;
> +		led-max-microamp = <20000>;
> +	};
> +
> +	led1b@1 {
> +		label = "ncp:power:blue";
> +		reg = <1>;
> +		led-max-microamp = <20000>;
> +	};
> +
> +	led1g@2 {
> +		label = "ncp:power:green";
> +		reg = <2>;
> +		led-max-microamp = <20000>;
> +	};
> +};
>


-- 
Best regards,
Jacek Anaszewski