Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 27 Mar 2003 12:08:07 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 27 Mar 2003 12:07:24 -0500 Received: from charger.oldcity.dca.net ([207.245.82.76]:12176 "EHLO charger.oldcity.dca.net") by vger.kernel.org with ESMTP id ; Thu, 27 Mar 2003 12:05:49 -0500 Date: Thu, 27 Mar 2003 12:16:38 -0500 From: "Mark M. Hoffman" To: Jean Delvare Cc: Jan Dittmer , azarah@gentoo.org, greg@kroah.com, mds@paradyne.com, linux-kernel@vger.kernel.org, linux@brodo.de, sensors@Stimpy.netroedge.com Subject: Re: lm sensors sysfs file structure Message-ID: <20030327171638.GA23888@earth.solarsys.private> Mail-Followup-To: Jean Delvare , Jan Dittmer , azarah@gentoo.org, greg@kroah.com, mds@paradyne.com, linux-kernel@vger.kernel.org, linux@brodo.de, sensors@Stimpy.netroedge.com References: <3E82024A.4000809@portrix.net> <20030326202622.GJ24689@kroah.com> <3E82292E.536D9196@paradyne.com> <20030326225234.GA27436@kroah.com> <3E82D678.9000807@portrix.net> <1048762244.4773.1258.camel@workshop.saharact.lan> <3E82EE25.3070308@portrix.net> <1048768432.4774.1263.camel@workshop.saharact.lan> <3E82F736.2000704@portrix.net> <20030327143140.0428fcd7.khali@linux-fr.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030327143140.0428fcd7.khali@linux-fr.org> User-Agent: Mutt/1.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2391 Lines: 55 * Jean Delvare [2003-03-27 14:31:40 +0100]: > > Ah, and I don't want to do small corrections like 1 or 2 percent up or > > or down, but things like this for lm80: > > compute in0 (24/14.7 + 1) * @ , @ / (24/14.7 + 1) > > compute in2 (22.1/30 + 1) * @ , @ / (22.1/30 + 1) > > compute in3 (2.8/1.9) * @, @ * 1.9/2.8 > > compute in4 (160/30.1 + 1) * @, @ / (160/30.1 + 1) > > > > These differ a lot. And as stated in the sensors.conf seem to be from > > the datasheet of the lm80 and not mainboard specific. > > They may be mainboard specific. The formulae rely on *suggested* > resistor values, which the integrators may or may not follow. There > definitely is a need for userspace conversion. Libsensors needs to be > tunable by the user. > > I don't know about the kernel conversion Jan is talking about (never > coded a sensor driver myself), so I can't talk about this half, but I'm > pretty sure you shouldn't even think of moving all conversions into > kernel space. > > Mark, Phil, maybe you could explain the reasons better than I would? I'm not the Mark to which Jean refers, but anyway... he is correct. The sensor chip cannot read temperatures directly, only voltage. The conversion from degress C to V is dependent on the mainboard for the reasons Jean mentions. But also, the chip driver cannot read voltage directly, only bits in a register. *That* conversion is *not* mainboard dependent; it is sensor chip specific. Even when the subject in question is voltage (e.g. power supply +12V), there is mainboard dependent nonsense between the "real value" and what is presented at the pin of the sensor chip. So there is a legitimate need for two conversions. IMHO, the mainboard dependent one *must* be done in userspace (as Jean says). But the conversion of raw register values to volts should happen in the kernel; fixed point maths are sufficient for that. (Yes I'm simplifying; external sensors can present data to sensors chips in other electrical formats, e.g. PWM. Same argument applies.) Regards, -- Mark M. Hoffman mhoffman@lightlink.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/