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From: "Måns Rullgård" <mans@mansr.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Pavel Machek <pavel@ucw.cz>, Alexandre Courbot <gnurou@gmail.com>,
	Felipe Balbi <balbi@ti.com>, Bryan Wu <cooloney@gmail.com>,
	Richard Purdie <rpurdie@rpsys.net>,
	"linux-leds\@vger.kernel.org" <linux-leds@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux OMAP Mailing List <linux-omap@vger.kernel.org>,
	"linux-gpio\@vger.kernel.org" <linux-gpio@vger.kernel.org>
Subject: Re: RGB LED control (was Re: "advanced" LED controllers)
Date: Mon, 09 Mar 2015 11:50:56 +0000	[thread overview]
Message-ID: <yw1xd24i1ja7.fsf@unicorn.mansr.com> (raw)
In-Reply-To: <CAMuHMdUVgZ1i5zymxmi3-i98n9UPTV=Sq-Oa=ieyfOzETW-DzA@mail.gmail.com> (Geert Uytterhoeven's message of "Mon, 9 Mar 2015 09:08:37 +0100")

Geert Uytterhoeven <geert@linux-m68k.org> writes:

> Hi Pavel,
>
> On Sun, Mar 8, 2015 at 9:57 PM, Pavel Machek <pavel@ucw.cz> wrote:
>> Ok, so I played with RGB LED a bit, and we have quite a gap in
>> documentation: what 50% brightness means is non-trivial and very
>> important in case we want to do smooth blinking and color transitions.
>>
>> Signed-off-by: Pavel Machek <pavel@ucw.cz>
>>
>> diff --git a/Documentation/ABI/testing/sysfs-class-led b/Documentation/ABI/testing/sysfs-class-led
>> index 3646ec8..649d7a6 100644
>> --- a/Documentation/ABI/testing/sysfs-class-led
>> +++ b/Documentation/ABI/testing/sysfs-class-led
>> @@ -8,6 +8,11 @@ Description:
>>                 non-zero brightness settings. The value is between 0 and
>>                 /sys/class/leds/<led>/max_brightness.
>>
>> +               If LED supports continuous brightness settings, 50% brightness
>> +               should correspond to 50% brightness perceived by human, in a similar
>> +               manner pixel brightness on monitor does (not 50% PWM).
>
> How many drivers do it right? How many don't?
>
> For those that don't, perhaps we handle the conversion between perceived and
> pwm in the core, e.g. by adding a new flag to led_classdev.flags to indicate
> the need for conversion?

Some LED controllers do the right thing in hardware, so any adjustment
done in the core needs to be optional.

-- 
Måns Rullgård
mans@mansr.com

  parent reply	other threads:[~2015-03-09 11:51 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-19 21:14 "advanced" LED controllers Felipe Balbi
2015-02-23 22:34 ` Pavel Machek
2015-02-23 22:58   ` Felipe Balbi
2015-02-25 21:49     ` Pavel Machek
2015-02-25 23:55       ` NeilBrown
2015-02-28 16:18         ` Pavel Machek
2015-02-25  8:25 ` Geert Uytterhoeven
2015-02-25  9:06   ` Alexandre Courbot
2015-03-02  9:21     ` Pavel Machek
2015-03-03  8:15       ` Alexandre Courbot
2015-03-08 20:57         ` RGB LED control (was Re: "advanced" LED controllers) Pavel Machek
2015-03-09  8:08           ` Geert Uytterhoeven
2015-03-09  9:08             ` Pavel Machek
2015-03-09 11:50             ` Måns Rullgård [this message]
2015-03-10  8:04               ` Pavel Machek
     [not found]                 ` <CAK5ve-K4jyBSVk1CZ8qQrFgevqdbhdsgZ1ZYX2e-t07494oq4A@mail.gmail.com>
2015-03-11  9:34                   ` Documentation: leds: clarify what 50% brightness means Pavel Machek

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