From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacek Anaszewski Subject: Re: [PATCH v5 1/4] leds: core: add generic support for RGB Color LED's Date: Thu, 31 Mar 2016 10:17:36 +0200 Message-ID: <56FCDD20.6060406@samsung.com> References: <56D608ED.2090406@gmail.com> <20160329100258.GA24964@amd> <56FAE7A8.2070302@gmail.com> <20160329214323.GA10455@amd> <56FB893C.60203@samsung.com> <20160330130319.GB19994@amd> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-reply-to: Sender: linux-kernel-owner@vger.kernel.org To: Heiner Kallweit Cc: Pavel Machek , pali.rohar@gmail.com, sre@kernel.org, khilman@kernel.org, aaro.koskinen@iki.fi, ivo.g.dimitrov.75@gmail.com, Patrik Bachan , serge@hallyn.com, Greg KH , linux-leds@vger.kernel.org, Benjamin Tissoires , Linux Kernel Mailing List , Linux USB Mailing List List-Id: linux-leds@vger.kernel.org Hi Heiner, On 03/30/2016 03:59 PM, Heiner Kallweit wrote: > On Wed, Mar 30, 2016 at 3:03 PM, Pavel Machek wrote: >> Hi! >> >>>> Ok, so: >>>> >>>> a) Do we want RGB leds to be handled by existing subsystem, or do we >>>> need separate layer on top of that? >>>> >>>> b) Does RGB make sense, or HSV? RGB is quite widely used in graphics, >>>> and it is what hardware implements. (But we'd need to do gamma >>>> correction). >>>> >>>> c) My hardware has "acceleration engine", LED is independend from >>>> CPU. That's rather big deal. Does yours? It seems to be quite common, >>>> at least in cellphones. >>>> >>>> Ideally, I'd like to have "triggers", but different ones. As in: if >>>> charging, do yellow " .xX" pattern. If fully charged, do green steady >>>> light. If message is waiting, do blue " x x" pattern. If none of >>>> above, do slow white blinking. (Plus priorities of events). But that's >>>> quite different from existing support...) >>> >>> Please note that HSV colour scheme allows to neatly project monochrome >>> brightness semantics on the RGB realm. I.e. you can have fixed >>> hue and saturation, and by changing the brightness component a perceived >>> colour intensity can be altered. >> >> I see HSV has some advantages. But we already have LEDs with multiple >> colors, and kernel already handles them: >> >> pavel@duo:~$ ls -1 /sys/class/leds/ >> tpacpi:green:batt >> tpacpi:orange:batt >> >> This is physically 2 leds but hidden under one indicator, so you got >> "off", "green", "orange" and "green+orange". > > That's a good example. As long as you can recognize green+orange as > separate lights/colors > (w/o magnifying glass) I wouldn't call it "a LED with multiple colors" > but "multiple > LED devices". > > In my use case we talk about RGB LEDs like the commonly used 5050 SMD RGB LEDs. > And it's not only about using a handful of discrete colors but about > displaying any arbitrary > color. > So far the kernel exposes the physical RGB LEDs as separate LEDs only > and I can't use > a trigger to e.g. set "magenta with 50% brightness". I think that we should consult more people before pushing the solution upstream. Would you mind writing a message with an explanation of the issue to linux-api list? Please keep in mind also the information from the "Attributes" section of Documentation/filesystems/sysfs.txt. -- Best regards, Jacek Anaszewski