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

Daniel Thompson
2018-03-20T11:22:12Z

On Mon, Mar 19, 2018 at 05:04:31PM +0100, Enric Balletbo Serra wrote:
> Hi Daniel,
>
> Gentle ping for this series, there is any possibility you have a
> chance to review it? Let me know if you want I change something.

I haven't got it in my TODO backlog... which means either I mistakenly
deleted it when it went through originally or that I deliberately deleted
it because I thought a v4 was coming along soon.

I could go diving through the archives if I need to but were there other
pending changes for this patchset?

Daniel.

>
> Thanks,
> Enric
>
> 2018-02-08 12:30 GMT+01:00 Enric Balletbo i Serra
> <enric.balletbo@collabora.com>:
> > 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.
> >
> > 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(-)
> >
> > --
> > 2.15.1
> >