GEOM will panic 6.0-current on userland wrong-length disk reads

Just discovered (and verified with latest build on 
current.freebsd.org) that the following will panic
the new GEOM fdc driver in 6.0-current:

# dd if=/dev/fd0 bs=55 
panic: wrong length 55 for sectorsize 512

And further checking, discovered that ALL disk devices will cause
a panic:

dd if=/dev/ad0 bs=1234
panic: wrong length 1234 for sectorsize 512

Perhaps this is geom's way of complaining?  Seems a rather radical
way to handle non-matching-blocksize reads of disk devices.  A
simple programming error reading a disk dev node will panic the
machine.

-scott