linux-kernel - Exponential LED brightness Re: [PATCH v4 0/6] leds: lm3692x: Allow to set ovp and brigthness mode

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Message-ID: <20200107133119.GA3825@duo.ucw.cz>
Date:   Tue, 7 Jan 2020 14:31:20 +0100
From:   Pavel Machek <pavel@....cz>
To:     Guido Günther <agx@...xcpu.org>
Cc:     Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Dan Murphy <dmurphy@...com>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Exponential LED brightness Re: [PATCH v4 0/6] leds: lm3692x: Allow
 to set ovp and brigthness mode

Hi!

> Overvoltage protection and brightness mode are currently hardcoded
> as 29V and disabled in the driver. Make these configurable via DT.
> 
> This v4 moves the exponential brightness mode to the back of the series
> as per Pavel's request:
> 
>   https://lore.kernel.org/linux-next/20200106103233.GA32426@amd/T/#m93270a9bf10b88e060f4e4cf5701c527476de985
> 
> The end result is identical and i've tested everything still works when
> dropping the last to patches and checked compiltion via

Thank you. Applied 1-4 (with some reformatting of changelog, and
led->LED).

Exponential mode:

We should decide if LEDs should be linear or not. Most LEDs are linear
now, and we may want to make it part of the API. Additional advantage
is that linear is "well defined". It is actually quite important for
RGB LEDs, because you get wrong colors otherwise.

(Non-linear can have advantages, too... like needing less bits.)

So, my suggestion is to document LEDs as linear, and leave
exponential->linear conversion to someone else.

Best regards,

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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