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

From: Lee Jones <lee.jones@linaro.org>
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>,
	Alexandru Stan <amstan@google.com>,
	linux-leds@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, kernel@collabora.com
Subject: Re: [PATCH v3 0/4] backlight: pwm_bl: support linear interpolation and brightness to human eye
Date: Mon, 9 Apr 2018 09:17:02 +0100	[thread overview]
Message-ID: <20180409081702.rwj773h6ndglnejm@dell> (raw)
In-Reply-To: <20180208113032.27810-1-enric.balletbo@collabora.com>

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
Linaro.org │ Open source software for ARM SoCs
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