From mboxrd@z Thu Jan  1 00:00:00 1970
From: Matthias Kaehlcke <mka@chromium.org>
Date: Mon, 22 Jul 2019 23:59:26 +0000
Subject: Re: [PATCH v3 0/4] backlight: Expose brightness curve type through sysfs
Message-Id: <20190722235926.GA250418@google.com>
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References: <20190709190007.91260-1-mka@chromium.org>
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To: Thierry Reding <thierry.reding@gmail.com>, Lee Jones <lee.jones@linaro.org>, Daniel Thompson <daniel.thompson@linaro.org>, Jingoo Han <jingoohan1@gmail.com>, Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: linux-pwm@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, Enric Balletbo i Serra <enric.balletbo@collabora.com>, Douglas Anderson <dianders@chromium.org>, Brian Norris <briannorris@chromium.org>, Pavel Machek <pavel@ucw.cz>, Jacek Anaszewski <jacek.anaszewski@gmail.com>

On Tue, Jul 09, 2019 at 12:00:03PM -0700, Matthias Kaehlcke wrote:
> Backlight brightness curves can have different shapes. The two main
> types are linear and non-linear curves. The human eye doesn't
> perceive linearly increasing/decreasing brightness as linear (see
> also 88ba95bedb79 "backlight: pwm_bl: Compute brightness of LED
> linearly to human eye"), hence many backlights use non-linear (often
> logarithmic) brightness curves. The type of curve is currently opaque
> to userspace, so userspace often relies on more or less reliable
> heuristics (like the number of brightness levels) to decide whether
> to treat a backlight device as linear or non-linear.
> 
> Export the type of the brightness curve via a new sysfs attribute.
> 
> Matthias Kaehlcke (4):
>   MAINTAINERS: Add entry for stable backlight sysfs ABI documentation
>   backlight: Expose brightness curve type through sysfs
>   backlight: pwm_bl: Set scale type for CIE 1931 curves
>   backlight: pwm_bl: Set scale type for brightness curves specified in
>     the DT
> 
>  .../ABI/testing/sysfs-class-backlight         | 26 ++++++++++++++
>  MAINTAINERS                                   |  2 ++
>  drivers/video/backlight/backlight.c           | 19 ++++++++++
>  drivers/video/backlight/pwm_bl.c              | 35 ++++++++++++++++++-
>  include/linux/backlight.h                     |  8 +++++
>  5 files changed, 89 insertions(+), 1 deletion(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-class-backlight

ping, any comments on v3?

Thanks

Matthias