USB patch for better bus_dma and detachment support

[Rob]

Ian Dowse wrote:
> In case anybody is interested in testing or helping with this,
> there's a patch at
> 
> 	http://people.freebsd.org/~iedowse/usb.diff
> 
> that attempts to begin addressing a number of problems with our
> current USB code:

Can I apply this patch also safely to STABLE?
If not, then, if you make a patch for STABLE, I would test it right away!

My umass storage USB toy, crashes the system when I umount it.
I blamed the USB chipset (VIA 83C572 USB controller), but am still not sure,
since I did not get much response from the STABLE list.

It would be great if your patch would solve the crash!

Regards,
Rob.