From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D60AFC433EF for ; Fri, 28 Jan 2022 23:04:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231497AbiA1XEG (ORCPT ); Fri, 28 Jan 2022 18:04:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48070 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230272AbiA1XEF (ORCPT ); Fri, 28 Jan 2022 18:04:05 -0500 Received: from mail-lj1-x231.google.com (mail-lj1-x231.google.com [IPv6:2a00:1450:4864:20::231]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 08DA3C061714; Fri, 28 Jan 2022 15:04:05 -0800 (PST) Received: by mail-lj1-x231.google.com with SMTP id a25so11078364lji.9; Fri, 28 Jan 2022 15:04:04 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=wYEgoZfpKoqG+5ywN2NTLN3ocA7SB43quho7NrzlcRU=; b=L+HJVHxgnWIvJJCp8rDWMfd2SQtd5ZqRh1d6eu36jRNZFPIkvlrDjh9xy6Sl9iYuEX iYlGcnyGV1pxi1rXdyJY4A8/23aJgh0hU/Po8jyGIaUVBiTBFBbSFkqFeTK+K57m2ZGE UqJEVUyz3J1X81VV2VpBcKlAVwhfSc6hBJQ1tZZLxbWaYwYRdSpkpXoSe8sz5rDY6QAw KF4YIBfcc2hvhHMG9RY31wvDxAupq/DYO5oV7394ULTE4XlG4FQF9eVugzau7WkCjDoA oyWRaJnyzNt7zXmWzvRvfTSOgxUXalqyA2iwuBqd7oYT3bLrzT1zr3BOPud8TjOtvdgj ZwBw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=wYEgoZfpKoqG+5ywN2NTLN3ocA7SB43quho7NrzlcRU=; b=M5N1m2dpplmgjrfUpYeKwpn9hGCVjkGlaYXkv6q/+0bb+8Kq64vpo3tE8scVbtaDj3 LukC07kopvF7Y/TLYcI8aLhcYpatJjnPsbcfuS8L2hOwGEqalvgPkvgtRIaSRVzyBr4x 1+RqYIc/kMJOkDo9xPVfIdhnl8sTFAyVMyCQE5Nu4drfoaS1yHUZByMtHQp82xQtbIKM BQ23IAoectHN9Xo6uCnPpMOgR4+L+8gBUSDCnz7rAV7xzgyT223csExQ87birsDewa32 zPbetk8Hj442x7X+7NEoEd5WIHQ7FKiGHdamJPMtO+1jHa1qQXYg5zf3nnsECX4FPIpm nW+g== X-Gm-Message-State: AOAM531CmQ/ZbplUY+aDN5PBBbio5oyfKxoHcOvY/uX9yoHKkWYQYOgs +L70C0aT8too08x0sRH451w= X-Google-Smtp-Source: ABdhPJwiVo/uSXQZ/cC6Fab0/D/UNev2UYpbI1VIp7bzNN0NTqqaQYBzm7iqXnGGRS7dPA2hVjRRuA== X-Received: by 2002:a2e:b8c7:: with SMTP id s7mr6349002ljp.49.1643411043062; Fri, 28 Jan 2022 15:04:03 -0800 (PST) Received: from [192.168.0.131] ([194.183.54.57]) by smtp.gmail.com with ESMTPSA id q7sm2482539lfg.221.2022.01.28.15.04.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 28 Jan 2022 15:04:02 -0800 (PST) Subject: Re: [PATCH v3 1/2] dt-bindings: leds: Add multicolor PWM LED bindings To: =?UTF-8?Q?Marek_Beh=c3=ban?= Cc: sven@svenschwermer.de, linux-leds@vger.kernel.org, devicetree@vger.kernel.org, linux-pwm@vger.kernel.org, Sven Schwermer , pavel@ucw.cz, robh+dt@kernel.org, thierry.reding@gmail.com, u.kleine-koenig@pengutronix.de, lee.jones@linaro.org, post@lespocky.de References: <20220126104844.246068-1-sven@svenschwermer.de> <20220126104844.246068-2-sven@svenschwermer.de> <00d8de09-360e-4e0f-1496-642ba1cbf863@gmail.com> <20220128213609.7a60e9fe@thinkpad> From: Jacek Anaszewski Message-ID: <09b46d05-5dd0-a585-2ca3-0bc04e613343@gmail.com> Date: Sat, 29 Jan 2022 00:04:01 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20220128213609.7a60e9fe@thinkpad> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-leds@vger.kernel.org On 1/28/22 9:36 PM, Marek Behún wrote: > On Thu, 27 Jan 2022 22:24:21 +0100 > Jacek Anaszewski wrote: > >> Hi Sven, >> >> On 1/26/22 11:48 AM, sven@svenschwermer.de wrote: >>> From: Sven Schwermer >>> >>> This allows to group multiple PWM-connected monochrome LEDs into >>> multicolor LEDs, e.g. RGB LEDs. >>> >>> Signed-off-by: Sven Schwermer >>> --- >> [...] >>> + >>> +additionalProperties: false >>> + >>> +examples: >>> + - | >>> + #include >>> + >>> + rgb-led { >>> + compatible = "pwm-leds-multicolor"; >>> + >>> + multi-led { >>> + color = ; >>> + function = LED_FUNCTION_INDICATOR; >>> + max-brightness = <65535>; >> >> It doesn't make much sense to have such a big resolution of global >> multi color brightness. 255 will be sufficient. > > If the PWM supports it, why not? > On Omnia the default is 255, and since it is PWM, the change from 0/255 > to 1/255 is much bigger then from, say, 15/255 to 16/255. So if 1/255 > is too bright, you are then unable to set it less bright. I think 1024 > or ever 65535 makes sense with PWMs. With values other than 255 we will not achieve 24-bit RGB, which is one problem, and the other one is non-linear brightness that can be achieved with PWM. So probably we would need to add an additional note in the documentation [0], saying that changing global brightness allows to preserve combined LED hue only when all sub-leds are linear, and that it will not be the case for PWM LEDs. And I propose to change multi-led 'color' DT property value from LED_COLOR_ID_RGB to LED_COLOR_ID_MULTI to avoid the impression that it will work as traditional 24-bit RGB. [0] Documentation/leds/leds-class-multicolor.rst -- Best regards, Jacek Anaszewski