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[216.228.112.22]) by smtp.gmail.com with ESMTPSA id j19sm107828pfr.155.2019.04.17.14.10.31 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 17 Apr 2019 14:10:31 -0700 (PDT) Date: Wed, 17 Apr 2019 14:10:26 -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: <20190417211026.GA9565@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> <20190417194817.GA22652@Asurada-Nvidia.nvidia.com> <20190417201234.GA6223@roeck-us.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190417201234.GA6223@roeck-us.net> 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 01:12:34PM -0700, Guenter Roeck wrote: > On Wed, Apr 17, 2019 at 12:48:18PM -0700, Nicolin Chen wrote: > > 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; > > } > > reg = (reg_config & mask) | val; > ret = regmap_write(reg); > if (ret) > return ret; > reg_config = reg; > > doesn't look that bad to me, and is much less costly. Okay. Will submit a change. Thanks