On Tue, 09 Jul 2019, 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> > --- > Feel free to suggest improvements in the documentation :) > > Changes in v3: > - removed composite strings, only keep 'linear', 'non-linear' and > 'unknown' > - updated sysfs attribute documentation > - updated commit message > > Changes in v2: > - changed order of brightness scale enums, explicitly make 'unknown' zero > - minor update of commit message > - deleted excess blank line after 'backlight_scale_types' > - s/curves/curve/ in sysfs doc > --- > .../ABI/testing/sysfs-class-backlight | 26 +++++++++++++++++++ > MAINTAINERS | 1 + > drivers/video/backlight/backlight.c | 19 ++++++++++++++ > include/linux/backlight.h | 8 ++++++ > 4 files changed, 54 insertions(+) > create mode 100644 Documentation/ABI/testing/sysfs-class-backlight Applied, thanks. -- Lee Jones [李琼斯] Linaro Services Technical Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
