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    SubjectRe: [PATCH v3 2/4] backlight: Expose brightness curve type through sysfs
    On Tue, Jul 09, 2019 at 12:00:05PM -0700, Matthias Kaehlcke wrote:
    > Backlight brightness curves can have different shapes. The two main
    > types are linear and non-linear curves. The human eye doesn't
    > perceive linearly increasing/decreasing brightness as linear (see
    > also 88ba95bedb79 "backlight: pwm_bl: Compute brightness of LED
    > linearly to human eye"), hence many backlights use non-linear (often
    > logarithmic) brightness curves. The type of curve currently is opaque
    > to userspace, so userspace often uses more or less reliable heuristics
    > (like the number of brightness levels) to decide whether to treat a
    > backlight device as linear or non-linear.
    >
    > Export the type of the brightness curve via the new sysfs attribute
    > 'scale'. The value of the attribute can be 'linear', 'non-linear' or
    > 'unknown'. For devices that don't provide information about the scale
    > of their brightness curve the value of the 'scale' attribute is 'unknown'.
    >
    > Signed-off-by: Matthias Kaehlcke <mka@chromium.org>

    I wonder what kind of problem you are solving here. Can you describe
    that in a few words?

    Best regards
    Uwe

    --
    Pengutronix e.K. | Uwe Kleine-König |
    Industrial Linux Solutions | http://www.pengutronix.de/ |

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