From: Pavel Machek <pavel@ucw.cz>
To: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Matthias Kaehlcke <mka@chromium.org>,
Thierry Reding <thierry.reding@gmail.com>,
Lee Jones <lee.jones@linaro.org>,
Jingoo Han <jingoohan1@gmail.com>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
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>,
Jacek Anaszewski <jacek.anaszewski@gmail.com>
Subject: Re: [PATCH v2 4/4] backlight: pwm_bl: Set scale type for brightness curves specified in the DT
Date: Fri, 28 Jun 2019 10:18:06 +0200 [thread overview]
Message-ID: <20190628081806.GA31375@amd> (raw)
In-Reply-To: <20190628075516.dwev7fxz7kmox2i2@holly.lan>
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On Fri 2019-06-28 08:55:16, Daniel Thompson wrote:
> On Wed, Jun 26, 2019 at 04:56:18PM +0200, Pavel Machek wrote:
> > On Mon 2019-06-24 13:31:13, Matthias Kaehlcke wrote:
> > > Check if a brightness curve specified in the device tree is linear or
> > > not and set the corresponding property accordingly. This makes the
> > > scale type available to userspace via the 'scale' sysfs attribute.
> > >
> > > To determine if a curve is linear it is compared to a interpolated linear
> > > curve between min and max brightness. The curve is considered linear if
> > > no value deviates more than +/-5% of ${brightness_range} from their
> > > interpolated value.
> >
> > I don't think this works. Some hardware does takes brightness in perceptual units,
> > converting it in the LED controller.
>
> This check is exclusive to PWM backlights so I'd like to double check
> that you are thinking specifically of hardware that takes it's signal
> from the PWM and works in perceptual units?
I missed that details. Taking PWM input then converting it to
perceptual units would indeed be strange.
Sorry,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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prev parent reply other threads:[~2019-06-28 8:18 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-24 20:31 [PATCH v2 0/4] backlight: Expose brightness curve type through sysfs Matthias Kaehlcke
2019-06-24 20:31 ` [PATCH v2 1/4] MAINTAINERS: Add entry for stable backlight sysfs ABI documentation Matthias Kaehlcke
2019-06-24 20:31 ` [PATCH v2 2/4] backlight: Expose brightness curve type through sysfs Matthias Kaehlcke
2019-06-26 14:56 ` Pavel Machek
2019-06-28 8:34 ` Daniel Thompson
2019-07-01 16:55 ` Matthias Kaehlcke
2019-06-24 20:31 ` [PATCH v2 3/4] backlight: pwm_bl: Set scale type for CIE 1931 curves Matthias Kaehlcke
2019-06-24 20:31 ` [PATCH v2 4/4] backlight: pwm_bl: Set scale type for brightness curves specified in the DT Matthias Kaehlcke
2019-06-26 14:56 ` Pavel Machek
2019-06-28 7:55 ` Daniel Thompson
2019-06-28 8:18 ` Pavel Machek [this message]
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