Re: [PATCH v3 0/4] backlight: pwm_bl: support linear interpolation and brightness to human eye

Lee Jones
2018-04-09T08:17:02Z

On Thu, 08 Feb 2018, Enric Balletbo i Serra wrote:

> Dear all,
>
> This series is a third patchset integrating the requested changes.
>
> 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.

Looks like you now have some positive feedback. :)

Could you please collect all of your received Acks and re-post this
set as a [RESEND] please?

> 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 | 34 ++-
> drivers/video/backlight/pwm_bl.c | 232 +++++++++++++++++++--
> 2 files changed, 246 insertions(+), 20 deletions(-)

--
Lee Jones [李琼斯]
Linaro Services Technical Lead
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