kern/106340: Need to control disk write cache on per-disk basis

[mjacob at freebsd.org]

> FreeBSD only allows setting disk write cache mode on a system wide basis,
> and only at boot time.  NetBSD allows setting the disk write cache mode
> of each disk individually, and does not require a reboot.  See the NetBSD
> dkctl(8) man page.

Which disks are you talking about? ATA disks?

For scsi disks you can do modepage edits via camcontrol that change it 
on a per-disk basis, so I assume you must be talking about ATA disks 
here, in which case it sounds like a simple addition to atacontrol(8).

-matt