hpsa driver and raid expand

I've just added 2 new disks to my HP server, expanded the array, and then expanded the volume. IIRC the old cciss driver would notify Linux that the device had expanded, but the hpsa driver doesn't appear to be doing this - /dev/sda is still the same size in /proc/partitions? Is there a way to force Linux to reprobe? I know Linux isn't Windows and I'll still need a reboot after expanding the partition (unless that's changed since I did it last?), but I still thought Linux could notice if a block device increased in size... Thanks James