From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ppsw-51.csi.cam.ac.uk ([131.111.8.151]:36855 "EHLO ppsw-51.csi.cam.ac.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751625Ab0JELgE (ORCPT ); Tue, 5 Oct 2010 07:36:04 -0400 Message-ID: <4CAB0EF0.3010606@cam.ac.uk> Date: Tue, 05 Oct 2010 12:41:36 +0100 From: Jonathan Cameron MIME-Version: 1.0 To: "Hennerich, Michael" CC: "linux-iio@vger.kernel.org" , Drivers Subject: Re: IIO_CONST_ATTR_SCAN_EL_TYPE add result shift? References: <544AC56F16B56944AEC3BD4E3D5917712F0DB8ACA8@LIMKCMBX1.ad.analog.com> In-Reply-To: <544AC56F16B56944AEC3BD4E3D5917712F0DB8ACA8@LIMKCMBX1.ad.analog.com> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On 10/05/10 12:24, Hennerich, Michael wrote: > /** > * IIO_CONST_ATTR_SCAN_EL_TYPE - attr to specify the data format of a scan el > * @name: the scan el name (may be more general and cover a set of scan elements > * @_sign: either s or u for signed or unsigned > * @_bits: number of actual bits occuplied by the value > * @_storagebits: number of bits _bits is padded to when read out of buffer > **/ > #define IIO_CONST_ATTR_SCAN_EL_TYPE(_name, _sign, _bits, _storagebits) \ > IIO_CONST_ATTR(_name##_type, #_sign#_bits"/"#_storagebits); > > There are cases where bits < storagebits and the result is not alligned to the LSB. > Lets say we have an 10-bit ADC. > The output is stored in a 16-bit word, with four leading zeros, then the 10-bit datum, followed by 2 don't care bits. > > So it would be good to provide an additional shift value? > Or how shall we handle these cases? This was discussed in the original debate and we simply proposed leaving it until we had a user. So the question is how to describe the shift. So taking your example, how about: u10/16>>2 Where the shift is optional. Other suggestions welcome given I made that up with 2 seconds thought. > > Greetings, > Michael > > Analog Devices GmbH Wilhelm-Wagenfeld-Str. 6 80807 Muenchen > Sitz der Gesellschaft Muenchen, Registergericht Muenchen HRB 4036 > Geschaeftsfuehrer Thomas Wessel, William A. Martin, Margaret Seif > > >