Re: [PATCH v3 2/4] backlight: Expose brightness curve type through sysfs

[Uwe Kleine-König]

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@xxxxxxxxxxxx>

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

Best regards
Uwe

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