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

On Wed, 3 Feb 2021 17:35:55 +0100
Pavel Machek [off-list ref] wrote:

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

quoted

Hello Pavel,
  

quoted

quoted

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

Is the property default-intensity documented in DT bindings?

Wouldn't it be better if the property was used in the multi-led node
instead of the channel node? I.e.
  multi-led@3 {
    color = <LED_COLOR_ID_RGB>;
    default-intensity = <100 0 0>;
  };