disk_create and cdevsw_add

[Sam]

'lo again,

kern/subr_disk.c:/^disk_create/ takes
two cdevsw types, and I only vaguely
understand why.  Can someone explain it to me?

I'm generally confused about resolving
entry points into the driver.  Does a
block device only get an open() after
registering it with disk_create?
Supposing I want to set some ioctls for
an aoecontrol utility (show all devices
known, eg), what would aoecontrol open
to ioctl?

Sam