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From:   Enric Balletbo Serra <eballetbo@gmail.com>
Date:   Mon, 19 Mar 2018 17:04:31 +0100
Message-ID: <CAFqH_52bXq76TnQLfnD0mohgr0d5iAcrHBcPefwnRB8gdbaYFQ@mail.gmail.com>
Subject: Re: [PATCH v3 0/4] backlight: pwm_bl: support linear interpolation
 and brightness to human eye
To:     Enric Balletbo i Serra <enric.balletbo@collabora.com>
Cc:     Daniel Thompson <daniel.thompson@linaro.org>,
        Doug Anderson <dianders@google.com>,
        Pavel Machek <pavel@ucw.cz>, Rob Herring <robh+dt@kernel.org>,
        Jingoo Han <jingoohan1@gmail.com>,
        Richard Purdie <rpurdie@rpsys.net>,
        Jacek Anaszewski <jacek.anaszewski@gmail.com>,
        Brian Norris <briannorris@google.com>,
        Guenter Roeck <groeck@google.com>,
        Lee Jones <lee.jones@linaro.org>,
        Alexandru Stan <amstan@google.com>, linux-leds@vger.kernel.org,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>, kernel@collabora.com
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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.

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
>