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Date: Tue, 27 Mar 2001 13:35:23 -0800 (PST)
From: Linus Torvalds <torvalds@transmeta.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
cc: "H. Peter Anvin" <hpa@transmeta.com>, <Andries.Brouwer@cwi.nl>,
        <linux-kernel@vger.kernel.org>, <tytso@MIT.EDU>
Subject: Re: Larger dev_t
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On Tue, 27 Mar 2001, Alan Cox wrote:
>
> > layer made it impossible for a driver writer to be nice to the user, so
> > instead they got their own major numbers.
>
> Not deficiencies in the SCSI layer, there is no way the scsi layer can
> handle high end raid controllers. In fact one of the reasons we can beat
> NT with some of these controllers is because NT does exactly what you
> suggest with scsi miniport driver hacks and it _sucks_. Its an ugly hack.

We could do this fairly _trivially_ today.

With absolutely no performance degradation.

With a simple "queue" mapping for the SCSI majors. Just look up which
queue to use for requests to which major, and you're done. The actual
IO may by-pass the SCSI layer altogether.

So I'm absolutely not advocating using the SCSI layer for the
high-end-disks. Rather the reverse. I'm advocating the SCSI layer not
hogging a major number, but letting low-level drivers get at _their_
requests directly.

		Linus

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