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 X-Spam-Level: X-Spam-Status: No, score=-7.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C872C433E0 for ; Thu, 9 Jul 2020 21:59:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4770E20672 for ; Thu, 9 Jul 2020 21:59:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="GI+IiJtf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726269AbgGIV7S (ORCPT ); Thu, 9 Jul 2020 17:59:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60802 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726213AbgGIV7R (ORCPT ); Thu, 9 Jul 2020 17:59:17 -0400 Received: from mail-ed1-x544.google.com (mail-ed1-x544.google.com [IPv6:2a00:1450:4864:20::544]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5C94AC08C5CE for ; Thu, 9 Jul 2020 14:59:17 -0700 (PDT) Received: by mail-ed1-x544.google.com with SMTP id bm28so1043174edb.2 for ; Thu, 09 Jul 2020 14:59:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=OxrZOzHbEor9to0nrlJocP/5Zuo+MSWeinZqDZd+gjU=; b=GI+IiJtfk+unqbse6tf84DkhwYMKWA4tcHgDRghIXscO5AANv9flZRH78abRtD7XMu j3CUdF8OUrEMm4XJL6DJWBvrzL/Jc9xrMEAhHe/FvpPuJZxj73Bjda9gNVyRg/ulN69p bIWVS03ZfQ1k0ShOxOQDxaRUp+u6KQv1V+/rsHhzHBXOPMvtE46AlC3A3KZcT8qpewyh h2PeSBkKI1/r0EKoIkDDAOtC0SW1XAdpekv3SrnkoWU2RH30mNpmeoDMUTttr+bIuOVC 1VIT04rE3QA41XeC6of9AKXi7eppAa2MYe12Vktu+cvHbV8AuiN9m2vUHyTs6gysqtL9 lmEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=OxrZOzHbEor9to0nrlJocP/5Zuo+MSWeinZqDZd+gjU=; b=JOPEuQCT/mnGlKL6XX1egC7b56E1iqamNSq8SWlG2UQGBTYKolCwy02m+qU25l3U9w VEkn01MCqUSPX6RjVpWQaMedTTt4n16kpUNz6W8iOlP9aYL/WWHptnyk18tSZHqVt6rF U+XZJEJTbn3PFo+HdGBjcESc0aUsEONgIMCy6Rh+7gaqUER3gyDlbNdifSDcYMtlaLM1 D0Ad5+u4tA3hpBfYNol5AxJjQllYcrbq7ZJGhEY9vBv/3+Wr7sW/OGtUj/YFPguWw1fq RhwBu7FS7T0hC4WOJQSF+XP7EUQblVuXi7hAXZAKujaknrMX2kg4Xf4sgnZbuDSRtHRG i2Yg== X-Gm-Message-State: AOAM532SbD7/H9TdZz+IHv8J7Z1gI5OGCftzB6JMcjWEUPKNi0V8MXxo 7A+DzzsOgUKGn+iPz5TkM4dlW/lMTcU= X-Google-Smtp-Source: ABdhPJx3vifeZwgf5aLRerKUbBzuQVhQ4fc3fsA1UrtE4HDNuSEUa4UgmphCYC+u3uUXxm4VRyYocA== X-Received: by 2002:a50:ee8a:: with SMTP id f10mr54312203edr.383.1594331955921; Thu, 09 Jul 2020 14:59:15 -0700 (PDT) Received: from ?IPv6:2a01:110f:b59:fd00:2066:8db:696f:8073? ([2a01:110f:b59:fd00:2066:8db:696f:8073]) by smtp.gmail.com with ESMTPSA id ce19sm2500982ejb.24.2020.07.09.14.59.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 09 Jul 2020 14:59:15 -0700 (PDT) Subject: Re: Query on using leds-gpio driver on a. GPIO with ACTIVE_HIGH To: Vishwanatha Subbanna , pavel@ucw.cz, dmurphy@ti.com, linux-leds@vger.kernel.org References: <30E1B20C-676E-45E2-9394-643262B5D04A@linux.vnet.ibm.com> From: Jacek Anaszewski Message-ID: <7a6f99d7-efaf-8771-9272-5fb5a555823f@gmail.com> Date: Thu, 9 Jul 2020 23:59:13 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <30E1B20C-676E-45E2-9394-643262B5D04A@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-leds-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-leds@vger.kernel.org Hi Vishwanatha, On 7/6/20 9:19 AM, Vishwanatha Subbanna wrote: > Hello, > > I have been a user of “leds-gpio” driver to manage the LEDs on IBM servers. So far, all these LEDs that were controlled by GPIO were ACTIVE_LOW. > > Example from DTS. > > fan3 { > retain-state-shutdown; > default-state = "keep"; > gpios = <&pca0 3 GPIO_ACTIVE_LOW>; > }; > > I wanted to know if it makes any difference to the user if the GPIO is ACTIVE_HIGH. I read through https://www.kernel.org/doc/Documentation/gpio/board.txt and it seemed we should be able to use it. > > However, going through https://github.com/torvalds/linux/blob/master/drivers/leds/leds-pca955x.c, I am not quite sure if the ACTIVE_HIGH can be used same as ACTIVE_LOW since I saw these : > > > #define PCA955X_LS_LED_ON 0x0 /* Output LOW */ > #define PCA955X_LS_LED_OFF 0x1 /* Output HI-Z */ > > #define PCA955X_GPO_HIGH LED_OFF > #define PCA955X_GPIO_LOW LED_FULL > > > This will be my DT entry : > > fan3 { > retain-state-shutdown; > default-state = "keep"; > gpios = <&pca0 3 GPIO_ACTIVE_HIGH>; > }; > > Will I be able to use the same “leds-gpio” interfaces irrespective of GPIO_LOW / GPIO_HIGH ? > > I use these interfaces today: > > echo 255 > brightness —> Turn Solid_ON > echo 0 > brightness —> Turn OFF > echo “timer” > trigger —> Initiate Blink > echo “none” > trigger —> Terminate Blink From what I can see in gpiolib sources GPIO_ACTIVE_LOW results in reversing the logic, i.e. pca955x_gpio_set_value() will be passed 0 when setting gpio to 1. Experience doesn't corroborate that? -- Best regards, Jacek Anaszewski