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 398BBC32792 for ; Wed, 24 Aug 2022 08:56:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234678AbiHXI4f (ORCPT ); Wed, 24 Aug 2022 04:56:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50704 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235831AbiHXI4d (ORCPT ); Wed, 24 Aug 2022 04:56:33 -0400 Received: from mail-qv1-xf29.google.com (mail-qv1-xf29.google.com [IPv6:2607:f8b0:4864:20::f29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 32778DF6C; Wed, 24 Aug 2022 01:56:32 -0700 (PDT) Received: by mail-qv1-xf29.google.com with SMTP id q8so12369205qvr.9; Wed, 24 Aug 2022 01:56:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc; bh=aWr8f4K8EXYtnB+iVG3NkWp+4Wg8K6TUAFF51MM2dC0=; b=GptCKFyBLh3Sa6C3Rc32Tze5USSgb7dLMD69Y9/pwWGhasKq78oavkxSQWOW/34iPp if6FeCQtmrhu8rrY2veHnFLKPmj9ccFgQmfpRrhIeYqg8QINGkfmwdUaEc+tDxOm1mZx 4ZKWwNMDxat1qYPW1uoMBGgBLX7iUGYaRkEt0Mcqq59gMhzRUM2v9S5kcyoZmmfc4Bsw NqOhvaMXns/sJfNft3+E2suL4dK2GGrHKqhNptr0nvi87n+zDdQPhaDe5sgkcW18TljQ JYfYXRSEbnqFNpT8gFOynPIlFzvZk0DPfd9yrBXSQQPlYf0zSAzv7BFfJK3w2SLlXRbp Aj/w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc; bh=aWr8f4K8EXYtnB+iVG3NkWp+4Wg8K6TUAFF51MM2dC0=; b=zzQZYOHbPX7sbRpOWPeqqvdRblsKL4HxiNr62qFBIOSOF9EF2AKMDDiuNnr2kgwkmD tQSpuXJP72r+Wv2WUBzNjjF11E7uSqPrthPWrZRqNVb/uJ1MzIqP8TqD/QTe2EOgAP2f EYDQuCuAuDHbdlQWUquzq4v15kHHRDvc7SK/S8046/AkuuwocLPk5beIVSlGnXXZIImB Szddl/Hsieo+tRmkYPaCu2cJ7bbqfYRiyOuJr4AHDAc4Wh9j5vNiy4uioBeSAXSAZVw3 erVi885tEILEsWqpSOeq0+XAHONCIKzN8IWNjWTGTzhNXkIUvUErayboBu7kzTQoH3n1 9Agw== X-Gm-Message-State: ACgBeo3kcT2SOaNTv6bBT05x9a7UvYWGwYuT/1s2QH4pOw4l6YlZpMyg YcXL0V0jBsvhw58B5pSHw4HsmAWEh+MLQSNA8GQ/GYTPxhE= X-Google-Smtp-Source: AA6agR5mKXme5smwP3Kmrr9PLM+r9XvtU8kyNpAfK8WSSYrfQaZdlhGmPkaqRaMtH4bi5Glnko5MMaAYxP762c/PnjE= X-Received: by 2002:a05:6214:c22:b0:497:10a8:3067 with SMTP id a2-20020a0562140c2200b0049710a83067mr2828504qvd.48.1661331391243; Wed, 24 Aug 2022 01:56:31 -0700 (PDT) MIME-Version: 1.0 References: <20220722081146.47262-1-jjhiblot@traphandler.com> <20220722081146.47262-3-jjhiblot@traphandler.com> <5ba34982-52c7-e41a-fba8-d88d93529e47@traphandler.com> <20220804210412.GA30210@duo.ucw.cz> <0663c616-97c8-444c-f390-275fae402453@traphandler.com> In-Reply-To: <0663c616-97c8-444c-f390-275fae402453@traphandler.com> From: Andy Shevchenko Date: Wed, 24 Aug 2022 11:55:54 +0300 Message-ID: Subject: Re: [RESEND PATCH v6 2/3] leds: Add driver for the TLC5925 LED controller To: Jean-Jacques Hiblot Cc: Pavel Machek , Rob Herring , Krzysztof Kozlowski , Linux LED Subsystem , devicetree , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 24, 2022 at 11:39 AM Jean-Jacques Hiblot wrote: > On 04/08/2022 23:04, Pavel Machek wrote: > > On Thu 2022-08-04 22:23:00, Jean-Jacques Hiblot wrote: > >> On 31/07/2022 21:28, Andy Shevchenko wrote: > >>> On Fri, Jul 22, 2022 at 10:14 AM Jean-Jacques Hiblot > >>> wrote: ... > >>> Sorry for my slowpokeness, but I just realized that this driver may > >>> not be needed. What is the difference to existing gpio-74x164? > >> It might work. However it might not be as practical and efficient as the > >> dedicated LED driver. > >> > >> I'll give a try. > > It is certainly preffered solution. If you decide to re-submit the > > driver anyway, please mention that we already have GPIO driver for > > compatible chip, and explain why this is superior. > sorry for the delay. I tried with the 74x164 gpio driver and it works > as expected. > > The only drawbacks are: > > - as-is the 74x164 gpio driver supports only one output-enable gpio. > However in practice I don't think multiple OE GPIOs will ever be used. Let's leave it to the case when it will be needed. So, we can skip this point. > - with this approach, every time a LED status is changed the whole > register has to be sent on the SPI bus. In other words, changes cannot > be coalesced. But isn't it the same as what you do in your driver? To me it looks like you send the entire range of the values each time you change one LED's brightness. I don't see any differences with the GPIO driver. > I don't know if this is enough to make a dedicated TLC5925 driver > desirable in the kernel. I don't think you have enough justification for a new driver. -- With Best Regards, Andy Shevchenko