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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 2934FC282DC for ; Wed, 17 Apr 2019 19:48:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E95A0205C9 for ; Wed, 17 Apr 2019 19:48:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="cluWanpm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733216AbfDQTsY (ORCPT ); Wed, 17 Apr 2019 15:48:24 -0400 Received: from mail-pg1-f195.google.com ([209.85.215.195]:37820 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729779AbfDQTsX (ORCPT ); Wed, 17 Apr 2019 15:48:23 -0400 Received: by mail-pg1-f195.google.com with SMTP id e6so25294pgc.4; Wed, 17 Apr 2019 12:48:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=jD4t7ZMs5EXCYZ5VFvTHZgqBtravUrGVeV/sa0xSuR4=; b=cluWanpmZqiOR7P42PjN3dbFGxEKxwX1T1gIp4j8LfPPFMxv2gdJvSRjYaKNuboZiY 3LkObegDKKXRb8yk68vpAouC/i2lKJvVoAWKwYnhqHUxRZKylXrSEd7hqMuKYoPwx5yD x65MUlO9nUICwqq84XA64RR4J0hIVrO+5disRQsZt84SmS/y9M9xrmh1hhJBvStWca4f X9uqHOnef3tqYsf2hnRi/P7R8FmWk9h7QJBEYbdGM5wi3WjPkaDA6W2sqDy+8MrdaeRc 7avb0/a5EzOWg0J//nJ9+8GDmYiXynoWgJ6Sg9lNadaaFYD01+u4lkbXRMqlriYs4nct poVQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=jD4t7ZMs5EXCYZ5VFvTHZgqBtravUrGVeV/sa0xSuR4=; b=LtLHWKRyF4t3OBX90N8M001V/zAfzH8osfJsBFvdj6LFc1SlIktadYaU1TQndxLJr/ OTym6pY0QcbdJFuRhjnHYGoto7wag4BSWTuTQwiVDyQTFFJDAwuTozHOd7QK4C7lDS30 68XPkdw+sJUi+nOmzEa/HWk2j6CnRl++JrVUfUhHoTRzTvgzI/dvRzV3vmHO3nATLvtK q50PE/ut3F7b8k9c8n5x04l0DE+uK2gDBpQr6s6LykEB5OdKaSDgfDRI4vPjMCrRwyPc wnGOsDK79I3m84wHM8OlLnuTsiso3MOtyf5tQDNquFuuKX3yNxf5IuNG5Zuh+cL36cfi +cSw== X-Gm-Message-State: APjAAAWgzuxNLENbApGkUc4jH4LtBjhU2mCvxRdL7y4xLXACOrAJLQr9 j09bmvGYH8LGzpQGc+pOvG5HhxK+pgw= X-Google-Smtp-Source: APXvYqzn4Us/DH4j4G8brnXuFuvn3QZpvWjZl4t28MDAC8itfhYrWOIf0c4ei9sRwx/5bUbf0H4/Tg== X-Received: by 2002:aa7:8384:: with SMTP id u4mr90877158pfm.214.1555530502912; Wed, 17 Apr 2019 12:48:22 -0700 (PDT) Received: from Asurada-Nvidia.nvidia.com (thunderhill.nvidia.com. [216.228.112.22]) by smtp.gmail.com with ESMTPSA id b2sm70423162pfo.150.2019.04.17.12.48.22 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 17 Apr 2019 12:48:22 -0700 (PDT) Date: Wed, 17 Apr 2019 12:48:18 -0700 From: Nicolin Chen To: Guenter Roeck Cc: jdelvare@suse.com, linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org, corbet@lwn.net, linux-doc@vger.kernel.org Subject: Re: [PATCH] hwmon: (ina3221) Add voltage conversion time settings Message-ID: <20190417194817.GA22652@Asurada-Nvidia.nvidia.com> References: <20190416235548.22733-1-nicoleotsuka@gmail.com> <1ad27385-e62a-d4f0-2590-c50458119f12@roeck-us.net> <2a193494-a33e-dac0-456a-241d7b3e59ad@roeck-us.net> <20190417183949.GB5073@Asurada-Nvidia.nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190417183949.GB5073@Asurada-Nvidia.nvidia.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 17, 2019 at 11:39:49AM -0700, Nicolin Chen wrote: > > Thinking about it ... does it even make sense to cache reg_config twice, > > or would it be better to just update the local copy and use regmap_write() > > to send it to the chip ? > > I remember the reason of adding the read-back was to prevent race > condition. But now we have mutex protections for all sysfs nodes, > maybe it's not necessary anymore. I will read the code carefully > and see if it's safe to remove it -- will do in a separate patch. I just recalled a second thought for the reason why I left them there as it'd logically require a copy to restore upon failure of regmap_write, that might not look so neat as the read-back: old_config = reg_config; reg_config &= mask; reg_config |= val; ret = regmap_write(reg_config); if (ret) { reg_config = old_config; return ret; } Would you prefer this?