Hi Santiago, On Fri, Sep 28, 2012, Santiago Carot wrote: > 2012/9/28 Johan Hedberg <johan.hedberg@xxxxxxxxx>: > > Hi Andrzej, > > > > On Tue, Sep 25, 2012, Andrzej Kaczmarek wrote: > >> + Measurement: > >> + > >> + int16 Exponent: > >> + int32 Mantissa: > >> + > >> + Measurement value is calculated as > >> + (Mantissa) x (10^Exponent) > >> + > >> + In case of invalid or missing data, > >> + Exponent is set to 0 and Mantissa is > >> + set to 2^23-1 (0x7FFFFF hexadecimal). > > > > Why aren't we using the D-Bus DOUBLE type for this? For invalid/missing > > data just leave out these values from the dict. No need to try to > > brute-force a 1:1 mapping from the protocol to D-Bus. > > We don't use double type here because these information is valuable > for upper profiles implementing a IEE11073-20601 protocol layer. This > fact is scarcely commented in HTP and better explained in former > specification where there is a need to pack both values (mantissa and > exponent) in special kind of APDUs. Of course we could provide the > double value here, but there will remain the need to know when an > special case occurs: NRes, NaN,INFINITY, -INFINITY. > > Furthermore, providing a double value here will force to upper > profiles to do extra stuff to calculate the mantissa and the exponent > values in order to create APDUs, beside they will have to deal with > impreccisions derivated to comparate float point numbers and so it > might make difficult to check when a special case has happened. > > these are, as far as I remember, the reasons which we did it in this > way. We were already talking about this fact in the mailing list in > the past but I don't find the thread right now. sorry This is good enough as a justification. I remembered we had discussed this before but for the details I needed to get my memory refreshed. Thanks. Johan -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
