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

[Jacek Anaszewski]

On 06/21/2016 05:28 PM, Jacek Anaszewski wrote:
> 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@xxxxxxxxxx>
> > ---
> >   .../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";

Please add also led-max-microamp to all child nodes in this example.

> > +    };
> > +
> > +    led1_b@1 {
> > +        label = "ncp:power:blue";
> > +        reg = <1>;
> > +    };
> > +
> > +    led1_g@2 {
> > +        label = "ncp:power:green";
> > +        reg = <2>;
> > +    };
> > +};


--
Best regards,
Jacek Anaszewski