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Date:   Wed, 26 Jun 2019 16:56:18 +0200
From:   Pavel Machek <>
To:     Matthias Kaehlcke <>
Cc:     Thierry Reding <>,
        Lee Jones <>,
        Daniel Thompson <>,
        Jingoo Han <>,
        Bartlomiej Zolnierkiewicz <>,,,,,
        Enric Balletbo i Serra <>,
        Douglas Anderson <>,
        Brian Norris <>,
        Jacek Anaszewski <>
Subject: Re: [PATCH v2 4/4] backlight: pwm_bl: Set scale type for brightness
 curves specified in the DT

On Mon 2019-06-24 13:31:13, Matthias Kaehlcke wrote:
> Check if a brightness curve specified in the device tree is linear or
> not and set the corresponding property accordingly. This makes the
> scale type available to userspace via the 'scale' sysfs attribute.
> To determine if a curve is linear it is compared to a interpolated linear
> curve between min and max brightness. The curve is considered linear if
> no value deviates more than +/-5% of ${brightness_range} from their
> interpolated value.

I don't think this works. Some hardware does takes brightness in perceptual units,
converting it in the LED controller.


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