Dear all, This series is a first patchset based on the discussion of two previous RFCs [1] and [2]. The first and second patch what tries to solve is the problem of granularity for high resolution PWMs. The idea is simple interpolate between 2 brightness values so we can have a high PWM duty cycle (a 16 bits PWM is up to 65535 possible steps) without having to list out every possible value in the dts. I think that this patch is required to not break backward compability, to be more flexible and also extend the functionality to be able to use high resolution PWM with enough steps to have a good UI experience in userspace. The thirth and fourth patch is a bit more ambicious, the idea is let decide the driver the brightness-levels required in function of the PWM resolution. To do this create a brightness-levels table filled with the CIE 1931 algorithm values to convert brightness to PWM duty cycle. More detailed info is available in the commit message of every patch. Both functionalities were tested on a Samsung Chromebook Plus (that has a 16 bits PWM) and a SL50 device (with a 8 bits PWM) Waiting for your feedback. [1] http://www.spinics.net/lists/devicetree/msg193262.html [2] https://lkml.org/lkml/2017/11/16/301 Best regards, Enric Balletbo i Serra (4): backlight: pwm_bl: linear interpolation between brightness-levels dt-bindings: pwm-backlight: add a num-interpolation-steps property. backlight: pwm_bl: compute brightness of LED linearly to human eye. dt-bindings: pwm-backlight: move brightness-levels to optional. .../bindings/leds/backlight/pwm-backlight.txt | 36 +++- drivers/video/backlight/pwm_bl.c | 237 +++++++++++++++++++-- 2 files changed, 253 insertions(+), 20 deletions(-) -- 2.15.1 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
