linux-kernel - Re: [PATCH] leds: led-core: Get rid of enum led

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Date:   Fri, 11 Dec 2020 19:31:52 +0100
From:   Marek Behun <marek.behun@....cz>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     Abanoub Sameh <abanoubsameh8@...il.com>,
        "pavel@....cz" <pavel@....cz>,
        "linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Abanoub Sameh <abanoubsameh@...tonmail.com>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] leds: led-core: Get rid of enum led_brightness

On Fri, 11 Dec 2020 14:08:43 +0000
David Laight <David.Laight@...LAB.COM> wrote:

> 
> More than 8 bits would be good.
> While not really relevant for actual 'brightness' it allows
> for 'strange' things be encoded in the brightness field.
>
> For instance we have some hardware that has RGB leds on it.
> They are a single device so it really needs a colour property.
> But it is more complex than that, between the driver and LED
> there is an FPGA - so it can modulate the LED output in many ways.
> As well as using PWM to change the brightness and (eg) 1/2HZ flashing
> it is possible to alternate between red and green to get a reasonable
> orange (works better than driving both at the same time!).

Please don't do that. Don't misuse brightness for other settings.
Instead try to implement the settings in other sysfs files, maybe even
make it generic. Document the new sysfs ABI. But to not encode
non-brightness properties into brightness.

For you multicolor example there is multicolor LED framework now in
kernel.

Marek