Re: [PATCH v3 1/2] dt-bindings: leds: Add multicolor PWM LED bindings

From: "Marek Behún" <marek.behun@nic.cz>
To: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: sven@svenschwermer.de, linux-leds@vger.kernel.org,
	devicetree@vger.kernel.org, linux-pwm@vger.kernel.org,
	Sven Schwermer <sven.schwermer@disruptive-technologies.com>,
	pavel@ucw.cz, robh+dt@kernel.org, thierry.reding@gmail.com,
	u.kleine-koenig@pengutronix.de, lee.jones@linaro.org,
	post@lespocky.de
Subject: Re: [PATCH v3 1/2] dt-bindings: leds: Add multicolor PWM LED bindings
Date: Fri, 28 Jan 2022 21:36:09 +0100	[thread overview]
Message-ID: <20220128213609.7a60e9fe@thinkpad> (raw)
In-Reply-To: <00d8de09-360e-4e0f-1496-642ba1cbf863@gmail.com>

On Thu, 27 Jan 2022 22:24:21 +0100
Jacek Anaszewski <jacek.anaszewski@gmail.com> wrote:

> Hi Sven,
> 
> On 1/26/22 11:48 AM, sven@svenschwermer.de wrote:
> > From: Sven Schwermer <sven.schwermer@disruptive-technologies.com>
> > 
> > This allows to group multiple PWM-connected monochrome LEDs into
> > multicolor LEDs, e.g. RGB LEDs.
> > 
> > Signed-off-by: Sven Schwermer <sven.schwermer@disruptive-technologies.com>
> > ---  
> [...]
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/leds/common.h>
> > +
> > +    rgb-led {
> > +        compatible = "pwm-leds-multicolor";
> > +
> > +        multi-led {
> > +          color = <LED_COLOR_ID_RGB>;
> > +          function = LED_FUNCTION_INDICATOR;
> > +          max-brightness = <65535>;  
> 
> It doesn't make much sense to have such a big resolution of global
> multi color brightness. 255 will be sufficient.

If the PWM supports it, why not?
On Omnia the default is 255, and since it is PWM, the change from 0/255
to 1/255 is much bigger then from, say, 15/255 to 16/255. So if 1/255
is too bright, you are then unable to set it less bright. I think 1024
or ever 65535 makes sense with PWMs.

Marek