[dm-crypt] Creating FEC data on the same device

Hi,
I am able to create the hash data for my rootfs in the same device by
specifying the --hash-offset.

For example,
             veritysetup format myDevice myDevice
--hash-offset=sizeOfmyDevice
This works fine and the hash data is appended at the end of rootfs.


Similarly, can we create hash data and fec data on the same device ?
As in, can we somehow do..
             veritysetup format myDevice myDevice
--hash-offset=sizeOfMyDevice --fec-device=myDevice --fec-roots=2
*--fec-offset=sizeOfmyDevice+sizeOfhashData*
I should be able to get a single image like,* |rootfs|Hashdata|fecData|*

In this case, How can we determine  the value for
sizeOfmyDevice+sizeOfhashData ?
Is it possible to do it ? or
it has to be a separate file or separate partition for fec data ?

Thanks,
Rizwan