ioctl32 (32bit compatability for a 64bit driver).. Any information at all?

[James Hansen <debian-amd64@f0rmula.com>]

I've been scouring google for a while, but can't find a great deal of 
information on adding 32bit compatibility to a 64bit driver.

I can see there are ioctl32_register and _unregister functions in the 
ch.c scsi driver, but would anyone know where to find more information 
about these?

Thanks

James