[367] in linux-scsi channel archive
Re: Reading more than buffersize
daemon@ATHENA.MIT.EDU (Eric Youngdale)
Fri Jul 14 03:03:41 1995
From: "Eric Youngdale" <eric@aib.com>
Date: Thu, 13 Jul 1995 21:50:27 -0400
In-Reply-To: Christian Ullenboom <ulliull@uni-paderborn.de>
"Reading more than buffersize" (Jul 13, 1:37pm)
To: Christian Ullenboom <ulliull@uni-paderborn.de>,
linux-scsi@vger.rutgers.edu
>So how can I get more then 4000 byte with a single read-command without
>patching the kernels buffersize. Scanning the whole page (8.5" x 14") at
>300dpi with 255 colors would lead to 10Megs of data !!!
I believe that the scsi-generics interface allows larger transfer
sizes (up to 32Kb, if I am not mistaken. You will probably still get
pauses in the output when you use this, but it may help.
If you are ambitious, you try and come up with a driver that
is a little more well-suited for scanners. I am thinking in terms of
something that would allow for (and attempt to take advantage of) multiple
outstanding commands. This would only work for drivers that are configured
to allow for multiple outstanding commands, and multiple commands per lun,
but in such cases you may be able to make the scanner "stream". I am
thinking that the user program requests 10Mb of data or some such, and the
scanner driver would break this up into a series of smaller I/O commands and
attempt to overlap them as much as possible.
-Eric
--
"The woods are lovely, dark and deep. But I have promises to keep,
And lines to code before I sleep, And lines to code before I sleep."
