linux-kernel - Screen brightness behaves _very_ differently across different machines

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Date:   Wed, 18 Apr 2018 23:24:34 +0200
From:   Pavel Machek <pavel@....cz>
To:     kernel list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-omap@...r.kernel.org, tony@...mide.com, sre@...nel.org,
        nekit1000@...il.com, mpartap@....net, merlijn@...zup.org
Subject: Screen brightness behaves _very_ differently across different
 machines

Hi!

I tried to run auto brightness settings tuned for Nokia N900 on Droid
4, and results were not nice.

So I tried matching brightness between Nokia N900 and Droid 4, and I
have a reason:

Brightness 1 on n900 corresponds to brightness _50_ on droid 4.

| n900 |  d4 |
|    1 |  50 |
|    2 |  70 |
|    6 | 100 |
|    8 | 120 |
|   20 | 130 |
|   30 | 140 |
|   40 | 150 |
|  100 | 180 |
|  128 | 190 |
|  150 | 200 |
|  200 | 210 |
|  255 | 220 |

Values are very approximate, I did manually. (Light sensors are funny,
Nokia seems to have calibscale on intensity input, which should be
unitless, but not on illumination input, which should be in lux. And
I'm not sure... is value_in_lux = illumination_input /
illumination_scale?)

I'll get some sleep now, if you know what is going on there, let me
know...

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

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