Re: Larger dev_t

Linus Torvalds
2001-03-27T21:37:17Z

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