Closed source hardware but open source firmware?

[FennecTECH]

Well im been a rockbox fan for a verry long time   and ive recently gotten my most recent device  im trying to calculte the disscharge rate for the rockbox firmware on my device
anyways heres the generic discharge curve  from the source code  and i need to rebuild a new disscharge and charging curve for my device  so i figured id ask here
ill battery bench the device and attach the two curves    it will take >48 hours to execute this operation because of the battery runtime of this device wich is more than 30 hours
here is the bit of code in question
http://git.rockbox.org/?p=rockbox.git;a=blob;f=firmware/target/arm/imx233/sansa-fuzeplus/powermgmt-fuzeplus.c;h=af87d7045d770f44cff3c79b57599d697f04332d;hb=HEAD