From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752850Ab0IFIlt (ORCPT ); Mon, 6 Sep 2010 04:41:49 -0400 Received: from relay02-haj2.antispameurope.com ([83.246.65.52]:50893 "EHLO relay02-haj2.antispameurope.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752554Ab0IFIls (ORCPT ); Mon, 6 Sep 2010 04:41:48 -0400 Message-ID: <4C84A93B.2050507@iis.fraunhofer.de> Date: Mon, 06 Sep 2010 10:41:31 +0200 From: Manuel Stahl User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.9.2.8) Gecko/20100802 Lightning/1.0b2 Thunderbird/3.1.2 MIME-Version: 1.0 To: LKML CC: "linux-iio@vger.kernel.org" Subject: [IIO] Proposal for sysfs attributes Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha1; boundary="------------ms070709020307020009040802" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a cryptographically signed message in MIME format. --------------ms070709020307020009040802 Content-Type: multipart/mixed; boundary="------------010807060400000800070702" This is a multi-part message in MIME format. --------------010807060400000800070702 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable Hi all, there were some sysfs userspace questions on linux-iio where we would=20 like to get some more comments on. First thing, there are some attributes describing the layout of a ring=20 buffer that can be read out via a char device. The buffer contains=20 several entries with each containing so called scan elements. All=20 entries have the same layout. It is described in a directory=20 scan_elements (see below) that contains three attributes per scan element= =2E > OK, no packed buffers for now, but we should implement variable > sample sizes for standard types. Indeed we already have this for > the timestamp, which is always 64 bit. > > To be compatible with future extensions we could have: > |- /sys/bus/iio/device0/buffer0/scan_elements/ > |- accel_x_en (0 or 1) > |- accel_x_type (i.e. s14/16, see *) > |- accel_x_index (position inside the buffer entry) > > * s14/16 means signed 14 bits, stored in 16 bits, right aligned. > If it's left aligned we can just modify the scale attribute and > give the 16 bit interpretation in _raw. Is the 's14/16' self explaining or should we use some other format? Is 'type' a good postfix for the attribute? Next question: how strictly we want to resamble the hwmon ABI? To sum up the discussion: Hwmon has files with the postfix _input to read values scaled to reasonable units for fixed point representation. So the units are sometimes scaled down to 'millis' e.g. millivolt, millidegree Celsius. We agreed that we want to keep this, whenever we use the _input postfix. For IIO there is also the postfix triple _raw, _scale and _offset, where the final value is calculated by (_raw + _offset) * _scale. Floating point values are allowed for any of these files. The question in place was: Do we want to resamble the 'milli' units or should we stick to standard SI units (radians, kelvin, etc.) as floating point math is necessary anyway. Regards, --=20 Dipl.-Inf. Manuel Stahl Fraunhofer-Institut f=C3=BCr Integrierte Schaltungen IIS - Leistungsoptimierte Systeme - Nordostpark 93 Telefon +49 (0)911/58061-6419 90411 N=C3=BCrnberg Fax +49 (0)911/58061-6398 http://www.iis.fraunhofer.de manuel.stahl@iis.fraunhofer.de --------------010807060400000800070702 Content-Type: text/x-vcard; charset=utf-8; name="manuel_stahl.vcf" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="manuel_stahl.vcf" YmVnaW46dmNhcmQNCmZuOk1hbnVlbCBTdGFobA0KbjpTdGFobDtNYW51ZWwNCmVtYWlsO2lu dGVybmV0Om1hbnVlbC5zdGFobEBpaXMuZnJhdW5ob2Zlci5kZQ0KdGVsO3dvcms6KzQ5IDkx MSA1ODA2MS02NDE5DQp4LW1vemlsbGEtaHRtbDpGQUxTRQ0KdmVyc2lvbjoyLjENCmVuZDp2 Y2FyZA0KDQo= --------------010807060400000800070702-- --------------ms070709020307020009040802 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature 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