From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754904AbcDAN3K (ORCPT ); Fri, 1 Apr 2016 09:29:10 -0400 Received: from mailout1.w1.samsung.com ([210.118.77.11]:15188 "EHLO mailout1.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752684AbcDAN3H (ORCPT ); Fri, 1 Apr 2016 09:29:07 -0400 X-AuditID: cbfec7f5-f792a6d000001302-09-56fe779f0cd8 Message-id: <56FE779B.9020602@samsung.com> Date: Fri, 01 Apr 2016 15:28:59 +0200 From: Jacek Anaszewski User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130804 Thunderbird/17.0.8 MIME-version: 1.0 To: Pavel Machek Cc: Heiner Kallweit , 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 Subject: Re: [PATCH v5 1/4] leds: core: add generic support for RGB Color LED's References: <56D608ED.2090406@gmail.com> <20160329100258.GA24964@amd> <56FAE7A8.2070302@gmail.com> <20160329214323.GA10455@amd> <56FB893C.60203@samsung.com> <20160330130319.GB19994@amd> <20160401125540.GC11860@amd> In-reply-to: <20160401125540.GC11860@amd> Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFupkkeLIzCtJLcpLzFFi42I5/e/4Fd355f/CDOZt07VY88LB4vqUzawW 5xbMYLRY9H4Gq8WSK4fYLZ5ufsxkcXnXHDaLrW/WASWWtTJbTDz9m8li4c0mZou7p46yWZy/ cI7d4vTuEgc+j52z7rJ7XNsd6XH460IWj02rOtk83j4M8Hi/7yqbx4rV39k9Pm+SC+CI4rJJ Sc3JLEst0rdL4MrYuNC14D13RdvKh8wNjNs5uxg5OSQETCRObJ7PDmGLSVy4t54NxBYSWMoo sXuFYRcjF5D9jFGiec9asASvgJbE/QfPmUFsFgFVievLdzCB2GwChhI/X7wGs0UFIiT+nN7H ClEvKPFj8j0WEFtEQF5ia98KZpChzAJbmSV2PpkNNkhYwF/i/MdGZohti5kkpm6aC7SNg4NT QFPi8EdPkBpmAWuJlZO2MULY8hKb17xlnsAoMAvJjllIymYhKVvAyLyKUTS1NLmgOCk910iv ODG3uDQvXS85P3cTIySCvu5gXHrM6hCjAAejEg/vjWl/w4RYE8uKK3MPMUpwMCuJ8Kbk/QsT 4k1JrKxKLcqPLyrNSS0+xCjNwaIkzjtz1/sQIYH0xJLU7NTUgtQimCwTB6dUA2MQS/+SJbYS q9z0WDIvP9sZZv/fWe9/xSJHbdlbx+/8fmx12iHx57/DXh53Dapnf7m/l5XTUEuQbdKKIoXs eWujn9ZKe3TdFew64PDr0R5ezosNdyXb9p4Nf8Vik/yW0YxfeHavJw9fZL918swJ5xdcqSzS LT3lrzDB/dexZ/z7ZzlNCF63+rUSS3FGoqEWc1FxIgBu4tHznAIAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/01/2016 02:55 PM, Pavel Machek wrote: > Hi! > >>> 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". > > Well, that's how it is currently handled. But for the user, it looks > as a LED with multiple colors. > >> 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". > > Why not? > > What do you do if you want to display magenta on your LCD? > > You compute RGB values, then display them. The main drawback is that you can't set the colour at one go, but have to set brightness of each LED class device (R,G,B) separately. It incurs delays between setting each colour component. It is also impossible to set arbitrary colour from a trigger. Similarly blinking with arbitrarily chosen colour from RGB palette is impossible if separate colour components are treated as separate LEDs. -- Best regards, Jacek Anaszewski