Re: WAPBL/cache flush and mfi(4)

[Michael van Elst <mlelstv%serpens.de@localhost>]

On Fri, Aug 24, 2012 at 08:52:06PM +0200, Manuel Bouyer wrote:
> 
> > The standard drivers always turn off write caching when the BBU
> > is not working.
> 
> No, this is something the user can control directly in firmware,
> at last with mfi(4) controllers.

Depends on the firmware, I have seen such controllers rejecting the
request to enable the write cache without BBU. Obviously you can
create configurations on some firmware versions that are not save,
but that's clearly printed in the firmware documentation.

I wouldn't care much about the non-BBU/write-cache case anyway. It
is inherently unsafe, wether you flush the cache or not, in particular
WAPBL doesn't help at all.

N.B. Can't a driver flush caches when shutting down or suspending
through the pmf framework?


Greetings,
-- 
                                Michael van Elst
Internet: mlelstv%serpens.de@localhost
                                "A potential Snark may lurk in every tree."