From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx49wnZVLB5yu1oXaPM37jzHRP+fwGz15jNUa14M1R+SFriWJIQbz/0hUxFdYds6y99RTsluK ARC-Seal: i=1; a=rsa-sha256; t=1523887254; cv=none; d=google.com; s=arc-20160816; b=iVGzfL2S1RhJ+Q4bXO0JiFleIiW4GdlNcLV/GKS/k+zUVW2MPAi87M9krhH+KA2keQ pclSRTBErCiCMPE6YcBxE/7TFQEuDQhYGz9dh96JLcBZtE0norGzy31sR6trmlDR0QLQ V3Vzxppi8cVn/ae3wLpQuweJilGNpREiiOenlzq87GTHd76CnBiUDHf5/wXGNScWnlQ/ y3BUxHVi5G034GCc1nwNYDjbT8AvbzhEi6Z/+fbEVeBfiBUlex/UdstVbudlaYk3T/ux +vPm2HYhUbQNWiip/gKWtbS5p7Cil5EBJ57SqEfXinqBPPCh5Wp78NtNjf+OdJH5d/pb rfzg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=spamdiagnosticmetadata:spamdiagnosticoutput :content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:organization:from:references:cc:to :subject:dkim-signature:arc-authentication-results; bh=zQ/h8FLawq/8Xb6rRQoDfs7RFdC5IUOIb271zwFeO+s=; b=onxA+ztetbAjq/uLaPfreNYIBUYgGvPbdw7VX34zYIqimZgruz7RUjajlqhQM9il+C 8Rt0J2abpommJSnEK6O3DOVqz1vQ7aPYu8RtoB8cPBZEGUhJp4HT2eMd8sJZRB99gxLG xdgJgDo002mYhOilI6f766ZQRj1e/Oaem5ARgV9LaZJPTbxTsiLmi+W2qQWLPy0AfAOh eIckHVuPefv/33gTsg7mm7518fD7K74k1cAlczaqXMkrAtbOhdRXTEjL3YQGQCG53aDK zQlOnBCkDWN7jvAKEmOGC69RwbEVSGkk8Ls7mZ0FfyhzQzXk2jcs2Nk7melozxHeDdm7 eF1g== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@axentia.se header.s=selector1 header.b=la/zXHga; spf=pass (google.com: domain of peda@axentia.se designates 104.47.0.121 as permitted sender) smtp.mailfrom=peda@axentia.se Authentication-Results: mx.google.com; dkim=pass header.i=@axentia.se header.s=selector1 header.b=la/zXHga; spf=pass (google.com: domain of peda@axentia.se designates 104.47.0.121 as permitted sender) smtp.mailfrom=peda@axentia.se Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=peda@axentia.se; Subject: Re: [PATCH v3 1/2] dt-bindings: iio: afe: add current-sense-shunt and voltage-divider To: linux-kernel@vger.kernel.org Cc: Jonathan Cameron , Hartmut Knaack , Lars-Peter Clausen , Peter Meerwald-Stadler , Rob Herring , Mark Rutland , "David S. Miller" , Mauro Carvalho Chehab , Greg Kroah-Hartman , Linus Walleij , Andrew Morton , Randy Dunlap , "Andrew F . Davis" , Fabio Estevam , linux-iio@vger.kernel.org, devicetree@vger.kernel.org References: <20180410152802.30958-1-peda@axentia.se> <20180410152802.30958-2-peda@axentia.se> From: Peter Rosin Organization: Axentia Technologies AB Message-ID: Date: Mon, 16 Apr 2018 16:00:44 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180410152802.30958-2-peda@axentia.se> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [85.226.244.23] X-ClientProxiedBy: HE1P195CA0007.EURP195.PROD.OUTLOOK.COM (2603:10a6:3:fd::17) To AM4PR0202MB2770.eurprd02.prod.outlook.com (2603:10a6:200:8c::20) X-MS-PublicTrafficType: Email X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(7021125)(5600026)(4534165)(7022125)(4603075)(4627221)(201702281549075)(7048125)(7024125)(7027125)(7028125)(7023125)(2017052603328)(7153060)(7193020);SRVR:AM4PR0202MB2770; 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12V, but divided down with a 22/200 > +voltage divider to adjust it to the ADC range. > + > +SYSV ADC GND > + + + + > + | .-----. | .----. | > + '--| 200 |-+-| 22 |--' > + '-----' '----' > + > +sysv { > + compatible = "voltage-divider"; > + io-channels = <&maxadc 1>; > + > + /* Multiply the ADC voltage by 222/22 to get the system voltage. */ > + numerator = <222>; /* 200 + 22 */ > + denominator = <22>; > +}; While I already got a reviewed-by from Rob, and maybe I shouldn't be stirring the pot, but I had an umpteenth look and I now think this one looks a bit odd. It shows a bit that it originates from when the compatible was the very generic "io-channel-unit-converter" in v1 of the series. What I mean is that a voltage divider presumable always gets you a lower voltage. Therefore, one would assume that the denominator should be larger than the numerator. The fact that this translates into the inverted fraction when calculating backwards through the voltage divider should probably not affect the binding. So, in the above example, I think it would make more sense to have numerator = <22>; denominator = <222>; /* 200 + 22 */ (and then, naturally, adjust the driver to invert the fraction) Comments? Cheers, Peter