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SubjectRe: SCSI tape blocks > 128k ?
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Alan Cox wrote:
[ Alan always cuts the attribution, but it was REW who wrote: ]
> > http://samba.anu.edu.au/cgi-bin/linux-patches/incoming?id=267
> >
> > The patch implements the bigbuffer support required for this use, and
> > patches "sg" to actually use it. A two-line patch will allow st to
> > also use this......
>
> Its a workable answer, but not the right one. The right one is to propogate
> the use of scatter gather better and eventually (2.3.x I hope) DMA to
> user pages. Modern SCSI controllers dont need 1Mbyte of linear memory
> for this. And non DMA old ones are generally sufficiently dumb you can
> implement scatter gather in the cpu driven byte copy routines

I agree completely that the scatter gather would be nice. However
that's a 2.3 issue.

The "required" I mentioned was on the assumption that this
scatter/gather won't be implemented anytime soon.

Video cameras and TV cards DO need linear memory, and would be able to
use the bigbuffers implemented by my patch.

To get my scanner working, I need a working solution. To say that a
scanner is now supported under Linux, I can't afford to have to change
every SCSI card driver there is.

Under MSWindows, you're lucky if your scanner works with the supplied
SCSI card. Try running the TWAIN driver on top of an ASPI driver for a
different card (e.g. you already had a SCSI card in your PC), and it
is unlikely to work.

The fun thing about Linux is that once it works with one supported
card, it should work with all of them. If I hack the SCSI driver that
I have (NCR 810) to do the scatter gather, all the others are still
lagging behind....

Roger.

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