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Subject: Re: [PATCH v7 1/5] leds: core: add generic support for RGB LED's
From: Karl Palsson <karlp@tweak.net.au>
To: "Heiner Kallweit" <hkallweit1@gmail.com>
Cc: "Benjamin Tissoires" <benjamin.tissoires@redhat.com>,
        "Jacek Anaszewski" <j.anaszewski@samsung.com>,
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Date: Sun, 06 Mar 2016 20:55:21 -0000
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Heiner Kallweit <hkallweit1@gmail.com> wrote:
> Add generic support for RGB LED's.
> 
> Basic idea is to use enum led_brightness also for the hue and
> saturation color components.This allows to implement the color
> extension w/o changes to struct led_classdev.
> 
> Select LEDS_RGB to enable building drivers using the RGB
> extension.
> 
> Flag LED_SET_HUE_SAT allows to specify that hue / saturation
> should be overridden even if the provided values are zero.
> 
> Some examples for writing values to
> /sys/class/leds/<xx>/brightness: (now also hex notation can be
> used)
> 
> 255 -> set full brightness and keep existing color if set 0 ->
> switch LED off but keep existing color so that it can be
> restored
>      if the LED is switched on again later
> 0x1000000 -> switch LED off and set also hue and saturation to
> 0 0x00ffff -> set full brightness, full saturation and set hue
> to 0 (red)
> 


I admit I hadn't seen this earlier, and I didn't spend all day
looking at previous attempts, but what's the motivation for
putting all this overloaded syntax into the "brightness" file? I
thought the point was to have a single value in each file, one of
the references I did find was
http://www.spinics.net/lists/linux-leds/msg02995.html Is there
some thread where this was decided as advantageous? Surely 0-255
for _brightness_ is what the brightness entry should do?

I'd like to set the rgb colour of a led (or hsv, that can be it's
own file too) and separately ramp the brightness up and down. I
also think it's substantially simpler and easier to use from the
user's point of view, which is surely the place you want easy
right?

Sincerely,
Karl Palsson

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