linux-kernel - AW: [PATCH v1] leds: lp50xx: add setting of default intensity from DT

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Date:   Wed, 3 Feb 2021 15:39:59 +0000
From:   Sven Schuchmann <schuchmann@...leissheimer.de>
To:     Pavel Machek <pavel@....cz>
CC:     Dan Murphy <dmurphy@...com>, Rob Herring <robh+dt@...nel.org>,
        "linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: AW: [PATCH v1] leds: lp50xx: add setting of default intensity from DT

Hello Pavel,

> > In order to use a multicolor-led together with a trigger
> > from DT the led needs to have an intensity set to see something.
> > The trigger changes the brightness of the led but if there
> > is no intensity we actually see nothing.
> >
> > This patch adds the ability to set the default intensity
> > of each led so that it is turned on from DT.
> 
> Do we need this to be configurable from device tree? Can we just set
> it to max or something?
> 
> Aha, this basically sets the initial color for LEDs the monochromatic
> triggers, right?

Let me try to explain in other words: I have one RGB-LED
which consists of 3 Colors. Each of the three colors (Red, Green, Blue) you have
to define in the DT. For example this is my setup for one RGB-LED which I wanted
to show the heartbeat in Red (half intensity):

                                multi-led@3 {
                                        #address-cells = <1>;
                                        #size-cells = <0>;
                                        reg = <0x3>;
                                        color = <LED_COLOR_ID_RGB>;

                                        linux,default-trigger = "heartbeat";
                                        function = LED_FUNCTION_HEARTBEAT;

                                        led-9 {
                                                color = <LED_COLOR_ID_RED>;
                                                default-intensity = <100>;
                                        };

                                        led-10 {
                                                color = <LED_COLOR_ID_GREEN>;
                                        };

                                        led-11 {
                                                color = <LED_COLOR_ID_BLUE>;
                                        };
                                };

If I would not have the default-intensity I would actually see nothing,
since the intensity (which goes from 0-255) of each led is initialized with 0.

I hope I could clarify this a little more?

Best Regards,

   Sven