Is an HP P812 (ciss(4) RAID) usable for ZFS?

[Mel Pilgrim]

I've gotten my hands on a couple of HP Smart Array P812 RAID 
controllers. They'd be a nice upgrade from the aging LSI cards I have 
now, but I'm not sure if they'll work.

I know they're supported by ciss(4), but my use case is ZFS and 
searching has gotten me conflicting answers. Some comments say there is 
an HBA mode flag that can be set, others say that flag doesn't work.

I know about the "make a bunch of 1-disk RAID 0 volumes" workaround, but 
that's leaving the RAID controller between ZFS and the disks, which I 
don't want to do.

Is an HP Smart Array P812 RAID card usable as an HBA for ZFS?