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

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Date:   Wed, 3 Feb 2021 17:35:55 +0100
From:   Pavel Machek <pavel@....cz>
To:     Sven Schuchmann <schuchmann@...leissheimer.de>
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: Re: [PATCH v1] leds: lp50xx: add setting of default intensity from DT

On Wed 2021-02-03 15:39:59, Sven Schuchmann wrote:
> 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?

Yes, sounds reasonable. Could we get default intensity of 100% on all
channels if nothing else is specified?

Or maybe simply "if intensity is not specified, start with 100%, and
use explicit =0 if other color is expected".

Best regards,
								Pavel
-- 
http://www.livejournal.com/~pavelmachek

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