usb/113977: Need a way to set mode of USB disk's write cache

[Dieter]

>Number:         113977
>Category:       usb
>Synopsis:       Need a way to set mode of USB disk's write cache
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-usb
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Jun 23 23:00:06 GMT 2007
>Closed-Date:
>Last-Modified:
>Originator:     Dieter
>Release:        6.2
>Organization:
>Environment:
6.2-RELEASE amd64
>Description:
Need a way to set a USB disk's write cache to write-through mode,
to prevent filesystem corruption.

As far as I can tell, putting "hw.ata.wc=0" in loader.conf
only affects directly connected PATA/SATA disks, not disks
connected via a USB-to-*ATA bridge.

Perhaps via camcontrol?  But "camcontrol modepage da0 -l -v"
returns nothing.

>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: