linux-kernel - RGB LED control (was Re: "advanced" LED controllers)

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Message-ID: <20150308205732.GA385@amd>
Date:	Sun, 8 Mar 2015 21:57:32 +0100
From:	Pavel Machek <pavel@....cz>
To:	Alexandre Courbot <gnurou@...il.com>
Cc:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Felipe Balbi <balbi@...com>, Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>,
	"linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>
Subject: RGB LED control (was Re: "advanced" LED controllers)


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@....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).
+
+
 What:		/sys/class/leds/<led>/max_brightness
 Date:		March 2006
 KernelVersion:	2.6.17


-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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