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@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@linaro.org
Daniel.