[Yaffs] the function "yaffs_ecc_calc_other" does not work?!

hey guys.i'm usng yaffs_ecc_calc_other() calculating ecc.the code is below:
unsigned char in_data[2048];
for(i=0;i<2048;i++)
{
in_data[i]=i;
}
struct yaffs_ecc_other ecc_value;
yaffs_ecc_calc_other(in_data,2048,&ecc_value);
after that,i print the ecc_value,but three member of it all are 0.is there
any problem?
or how to use the ecc function that yaffs provided in yaffs_ecc.h? i'm
puzzling about it that how the ecc values stores?

thanks a lot.
----
Regards,
Ezio.