Subject: Re: Promise IDE patches
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Jan Niehusmann <jan@gondor.com>
Cc: Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>,
       Marcelo Tosatti <marcelo@conectiva.com.br>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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	 <200308270054.27375.bzolnier@elka.pw.edu.pl>
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Date: 27 Aug 2003 16:45:27 +0100
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On Mer, 2003-08-27 at 16:12, Jan Niehusmann wrote:
> On Wed, Aug 27, 2003 at 03:59:52PM +0100, Alan Cox wrote:
> > If you fail to do this then existing PIO LBA48 setups will just die
> > on boot.
> 
> But 'die on boot' is much better than 'silently currupt data', don't you
> think? 
> Still, a proper fix would work in all cases... 

You'd prevent people from using valid working file systems in ways
that don't corrupt.

I think the logic we need is something like

	if drive_is_lba48 && controller_doesnt_do_lba48
		clip_capacity

as a variant of the current change. That covers the "no way" case. For
the others we need to check capacity requires lba48 && !dma_lba48
somewhere, probably ide_dma_check. That would make us drop out of DMA
for unsafe setups in a way that doesnt cause crashes or suprises and
still let everyone access the data properly.

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