linux-kernel - AW: [PATCH v2 1/4] leds: lp50xx: add setting of default intensity from DT

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Message-ID: <DB8P190MB06344FAD6492E56D28A4E916D9B19@DB8P190MB0634.EURP190.PROD.OUTLOOK.COM>
Date:   Sat, 6 Feb 2021 13:14:33 +0000
From:   Sven Schuchmann <schuchmann@...leissheimer.de>
To:     Jacek Anaszewski <jacek.anaszewski@...il.com>,
        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 v2 1/4] leds: lp50xx: add setting of default intensity
 from DT

Hello Dan,

> Von: Jacek Anaszewski <jacek.anaszewski@...il.com>
> Gesendet: Freitag, 5. Februar 2021 19:37
> Hi Pavel,
> 
> On 2/5/21 11:23 AM, Pavel Machek wrote:
> > Hi!
> >
> >>>>       patternProperties:
> >>>>         "(^led-[0-9a-f]$|led)":
> >>>> @@ -99,6 +104,7 @@ examples:
> >>>>                  reg = <0x1>;
> >>>>                  color = <LED_COLOR_ID_RGB>;
> >>>>                  function = LED_FUNCTION_CHARGING;
> >>>> +               default-intensity = <100 0 0>;
> 
> How will you know which array position is for which child LED?
> I presume DT child nodes are not guaranteed to be parsed in the order
> of declaration?

I tried to fiddle this out, but it seems Jacek is right over here.
The multi-led definition looks like this (from the documentation leds-lp50xx.yaml)

        multi-led@1 {
               #address-cells = <1>;
               #size-cells = <0>;
               reg = <0x1>;
               color = <LED_COLOR_ID_RGB>;
               function = LED_FUNCTION_CHARGING;

               led-0 {
                   color = <LED_COLOR_ID_RED>;
               };

               led-1 {
                   color = <LED_COLOR_ID_GREEN>;
               };

               led-2 {
                   color = <LED_COLOR_ID_BLUE>;
               };
          };

But it seems that the color definition of each led is ignored.
By ignored I mean the driver does not take care which color
is at which position. So if I change led-0 to be LED_COLOR_ID_BLUE
and led-2 to be LED_COLOR_ID_RED nothing will change if I write
from userspace. Could you help to clarify?
Then it is even hard to know which led to set with default-intensity.

Also it seems that the enumeration of the multi-leds should
start with multi-led@0 (and not 1 as in the documentation).

Best Regards,

   Sven