On Tue, Sep 14, 2010 at 10:57:19AM -0400, Jean Delvare wrote: > On Tue, 14 Sep 2010 05:01:28 -0700, Guenter Roeck wrote: > > Hi Jean, > > > > On Tue, Sep 14, 2010 at 04:08:33AM -0400, Jean Delvare wrote: > > > On Mon, 13 Sep 2010 11:09:06 -0700, Guenter Roeck wrote: > > > > On Mon, Sep 13, 2010 at 01:41:21PM -0400, Jean Delvare wrote: > > > > > Not too sure about that. I had the same reaction at first, but do we > > > > > actually know of devices where the resolution isn't global? > > > > > > > > Yes, in the lm90 driver. Only max6657/58/59 and max6646 have extended local > > > > temperatures, all other chips have only 8 bit resolution for the local temperature. > > > > Remote temperatures are all extended, ie have higher resoution. > > > > > > But resolution can't be changed on these chips, can it? I think the > > > > Correct. > > > > > main purpose of these files is to let the user change the resolution > > > for chips which support this (usually this is an update speed / > > > resolution trade-off). Or do you believe that having read-only > > > attributes exposing fixed resolutions would be valuable? > > > > > Good point. Probably not really. More like nice to have. > > > > > I'm a little worried because resolution as a bit number isn't too > > > informative and doesn't quite work as a device-independent value. If > > > you really want the information to be exposed to user-space for all > > > devices, then we'd rather use actual sensor units (mV, m°C, whatever) > > > for resolution, and possibly add other attributes for the range. But > > > > I assumed it would be in units. Not sure how to express resolution > > as bit number in the first place. > > This is how datasheets usually refer to the future. The configuration > bits let the user select between 9-, 10, 11 and 12-bit resolution ADC > (with increasing integration time.) > > As most temperature sensors we deal with agree that 9-bit resolution > means LSB weight of 0.5°C, it could almost be used as a standard. But > of course there could be a device doing things differently someday, > which is why we probably don't want to use the ADC bit notation. > Agreed. > > > this means adding a whole lot of attribute files for some devices (if > > > we do it on a per-channel basis), so we first have to determine whether > > > it is really worth it. I don't think it is, but you can try and > > > convince me. > > > > Thinking about it, I'd rather keep it in mind in case someone else > > sees the need to it and convinces both of us... > > > > Another question if both attributes (rate and resolution) would make sense > > as module parameters instead. Are those attributes expected to vary across > > multiple instances of the same driver ? > > I see no reason to use module parameters for these. It does make sense > to use different settings on different chips in the same family (e.g. > one is on the motherboard and the other on the graphics adapter), plus > sysfs attribute values are easier to change at run-time (these > attributes could even be added to libsensors.) > Makes sense. Guenter _______________________________________________ lm-sensors mailing list lm-sensors@xxxxxxxxxxxxxx http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
