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

[Daniel Thompson]

On 07/08/2019 21:15, Matthias Kaehlcke wrote:
> 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 at chromium.org>
> 
> Daniel (et al): do you have any more comments on this patch/series or
> is it ready to land?

I decided to leave it for a long while for others to review since I'm 
still a tiny bit uneasy about the linear/non-linear terminology.

However that's my only concern, its fairly minor and I've dragged by 
feet for more then long enough, so:
Reviewed-by: Daniel Thompson <daniel.thompson at linaro.org>


Daniel.