Re: Backtracking in color scanning

Rogier Wolff (R.E.Wolff@BitWizard.nl)
Sun, 7 Sep 1997 13:53:49 +0200 (MET DST)

Wolfgang Jung wrote:
>
> It shouldn't be to much work to write a doube buffering sg.o, so
> if activated by some FLAG you could issue a read prior getting the data
> to userspace...(ie: just do another write)
> this should be at least be quick enough to ensure a small set of
> microsseconds between reads.

But as David and I were suggesting:

try adding
if (data_size > 0x1000) return

somewhere in the sg_read, just before the copy of the data from kernel
to userspace. you don't expect to get an image if you do that, but if
the scanner stops backtracking, it is worth it to implement the much
harder double buffering sg.....

> But I could imagine that the scanner itself does the backtracking if
> the read finishes.

Correct, so if the above doesn't help, we should look into allowing
longer "read" commands.

> in Gray mode ie: it does NO backtracking.
> but somehow trows some lines away :(

Hmm. Bug in the scanner?

Roger.

-- 
** R.E.Wolff@BitWizard.nl ** +31-15-2137555 ** http://www.BitWizard.nl/ **
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