On Sat, 9 Jan 2010 00:01:44 +0800, Huaxu Wan wrote: > On 11:28 Fri 08 Jan, Jean Delvare wrote: > > Hi Huaxu, > > > > On Fri, 8 Jan 2010 17:23:27 +0800, Huaxu Wan wrote: > > > > > > hwmon: (coretemp) Check the sensor existence instead of enumeration. > > > > > > The processor supports a digital thermal sensor if CPUID.06H.EAX[0] = 1. > > > > > > Signed-off-by: Huaxu Wan <huaxu.wan@xxxxxxxxxxxxxxx> > > > > > > --- > > > Documentation/hwmon/coretemp | 3 --- > > > drivers/hwmon/coretemp.c | 24 +++++++----------------- > > > 2 files changed, 7 insertions(+), 20 deletions(-) > > > > > > > Hmm. I don't like it for two reasons: > > > > * Which guarantee do we have that "the processor supports a digital > > thermal sensor" implies that this digital thermal sensor is > > compatible with what the Core/Core2/Atom have? Couldn't the format > > change in the future? > > It's quote from page 612 of Software Developer’s Manual V3A[1](14.5.5 On > Die Digital Thermal Sensors). Look from the history, I think it's > compatible with Core/Core2/Atom and even the feature CPU. Actually, this > patch has tested on old P4, Core2, i3(launched today?) system, all works > as expected. > > [1] http://www.intel.com/Assets/PDF/manual/253668.pdf $ wget http://www.intel.com/Assets/PDF/manual/253668.pdf --2010-01-08 19:05:33-- http://www.intel.com/Assets/PDF/manual/253668.pdf Resolving www.intel.com... 88.221.93.91, 88.221.93.112 Connecting to www.intel.com|88.221.93.91|:80... connected. HTTP request sent, awaiting response... 403 Forbidden 2010-01-08 19:05:33 ERROR 403: Forbidden. $ I am not worried about past models. I am worried about future models which could feature a different implementation of the thermal sensor. > > * Each CPU model has its own high temperature limit, which we use to > > compute the current temperature. So we can't pretend that we support > > all future CPU models, we really do not. Just look at how complex > > function adjust_tjmax is. > > > > TjMax varies with specific CPU series, sometimes even different within > same modle for industrial temperature. At this point, we can't support > all feature CPU models, but we can support all the released CPUs. I had > a plan to make an investigation about those. > > > It would only make sense to have "universal" support if the driver > > could report a relative value. Unfortunately our sysfs interface > > doesn't support this, although there have been discussions on that > > topic lately: > > > > http://thread.gmane.org/gmane.linux.drivers.sensors/20721/focus=917317 > > > > This patch avoid to patch everytime for new release CPU. We foucs on > the adjust_tjmax function calibration. I think the effort is much less > than calibration for each CPU model. Effort is one thing. Telling the user that we support his/her CPU when we don't really (and thus potentially report wrong temperature values) is another. I think this is simply not acceptable. > BTW, I saw openBSD[2] use the CPUID.06H.EAX[0] to identify the sensor. > > [2] http://archives.neohapsis.com/archives/openbsd/2007-05/2506.html I am not opposed to using this bit. What I am opposed to is using this bit as a replacement for the list of known supported CPU models. This bit could be used to exit quickly on unsupported models and let the user know when they have a CPU that isn't yet supported but could be. That would be better than our current code for that. -- Jean Delvare _______________________________________________ lm-sensors mailing list lm-sensors@xxxxxxxxxxxxxx http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
