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Date: Fri, 21 Dec 2007 14:30:28 +0100
To: Matthew Wilcox <matthew@wil.cx>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
       Benjamin Herrenschmidt <benh@kernel.crashing.org>,
       linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
       rdreier@cisco.com, linux-scsi@vger.kernel.org, rmk@arm.linux.org.uk,
       davem@davemloft.net, james.bottomley@steeleye.com, ralf@linux-mips.org
Subject: Re: [PATCH 2/2] scsi: Use new __dma_buffer to align sense buffer in scsi_cmnd
Message-ID: <20071221133027.GA11495@alpha.franken.de>
References: <20071221023011.4C4BADDDFA@ozlabs.org> <20071221103326.7ce1bc4f@the-village.bc.nu> <20071221131640.GN29690@parisc-linux.org>
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From: tsbogend@alpha.franken.de (Thomas Bogendoerfer)
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On Fri, Dec 21, 2007 at 06:16:41AM -0700, Matthew Wilcox wrote:
> On Fri, Dec 21, 2007 at 10:33:26AM +0000, Alan Cox wrote:
> > On Fri, 21 Dec 2007 13:30:08 +1100
> > Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> > 
> > > The sense buffer ins scsi_cmnd can nowadays be DMA'ed into directly
> > > by some low level drivers (that typically happens with USB mass
> > > storage).
> > 
> > Should that not be fixed in USB storage by using pci_alloc_coherent on the
> > PCI device of the hub not peeing directly into kernel space ?
> 
> That's what I said, but Ben seems fixated on this particular fix.

there are SCSI host drivers, which also DMA to the sense buffer like
sgiwd93.c for example.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessary a
good idea.                                                [ RFC1925, 2.3 ]