Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751469AbdGQVoX convert rfc822-to-8bit (ORCPT ); Mon, 17 Jul 2017 17:44:23 -0400 Received: from mail-out-2.itc.rwth-aachen.de ([134.130.5.47]:30645 "EHLO mail-out-2.itc.rwth-aachen.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751318AbdGQVoV (ORCPT ); Mon, 17 Jul 2017 17:44:21 -0400 X-IronPort-AV: E=Sophos;i="5.40,375,1496095200"; d="scan'208";a="4210665" From: =?iso-8859-1?Q?Br=FCns=2C_Stefan?= To: Jonathan Cameron CC: "linux-iio@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Hartmut Knaack , Lars-Peter Clausen , "Peter Meerwald-Stadler" Subject: Re: [PATCH 2/2] iio: Documentation: Add ina2xx shunt_resistor attribute documentation Thread-Topic: [PATCH 2/2] iio: Documentation: Add ina2xx shunt_resistor attribute documentation Thread-Index: AQHS/z7OZfIMwubyVE2P82Dm8d87h6JYa6oA Date: Mon, 17 Jul 2017 21:44:19 +0000 Message-ID: <10350930.kllyJhgabW@sbruens-linux> References: <20170716233410.22880-1-stefan.bruens@rwth-aachen.de> <2351a045a0564f5bb2af6c652d1fa5e3@rwthex-w2-b.rwth-ad.de> <20170717215357.6452f0f5@kernel.org> In-Reply-To: <20170717215357.6452f0f5@kernel.org> Accept-Language: en-US, de-DE Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-messagesentrepresentingtype: 1 x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [78.35.13.203] Content-Type: text/plain; charset="iso-8859-1" Content-ID: Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2382 Lines: 64 On Montag, 17. Juli 2017 22:53:57 CEST Jonathan Cameron wrote: > On Mon, 17 Jul 2017 01:34:10 +0200 > > Stefan Br?ns wrote: > > The ina2xx driver appeared in the Linux kernel version 4.5, but provided > > no documentation. Contrary to other uses of resistance in IIO, ina2xx uses > > microohms instead of ohms in the sysfs attribute. > > > > Signed-off-by: Stefan Br?ns > > This has me confused. The documentation is already > there and lists it as being in ohms. Which obviously, from reading the source code, is wrong - it uses microohms. Also, the current Description contains IMHO irrelevant stuff: "The value of the shunt resistor may be known only at runtime fom an eeprom content read by a client application." > Ah, subtle filename difference. Docs in are > Documentation/ABI/testing/sysfs-bus-iio-ina2xx-adc Well spotted ... > This attribute effectively exists for other parts > as well now. My grep foo failed me here, the only parts I could find are the MAX9611 (which specifies and uses ohms) and the INA2xx. adc/qcom-spmi-iadc.c allows to read the RSENSE value from device tree (specified in microohms), but does not expose it via sysfs. Can you point me to other devices? Slightly off-topic: Some attributes in iio are read from device-tree (e.g. shunt resistor values), should the iio documentation point to the dt bindings? Currently, only mount_matrix in sysfs-bus-iio vaguely mentions device-tree. Kind regards, Stefan > > --- > > > > Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc | 7 +++++++ > > 1 file changed, 7 insertions(+) > > create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc > > > > diff --git a/Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc > > b/Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc new file mode > > 100644 > > index 000000000000..9525098f6822 > > --- /dev/null > > +++ b/Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc > > @@ -0,0 +1,7 @@ > > +What: /sys/bus/iio/devices/iio:deviceX/in_shunt_resistor > > +Date: December 2015 > > +KernelVersion: 4.5 > > +Contact: linux-iio@vger.kernel.org > > +Description: The value of the shunt resistor connected to the V_IN+ and > > V_IN- + inputs, used to compute the current flowing through the shunt > > and + the corresponding power. In microohms.