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From: root@deadline.snafu.de (Andreas S. Wetzel)
Subject: Need help on writing SCSI scanner driver
To: hackers@freebsd.org
Date: Sat, 2 Aug 1997 12:31:42 +0200 (CEST)
Organization: A world stranger than you have ever imagined.
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Hi!
---

Some time ago I started to write a high level SCSI driver for my
AGFA Studio Star scanner. Now I'm facing some minor problems in
the overall design of the driver code. My imagination of a scanner
driver has been to have a device that is opened by the application
software by a open(2) call and than configured to the correct scan
parameters using ioctls before the scan data is retrieved via one
or more read(2) calls. The problem in this context seems to be
that the scanner is in fact able to deliver all the scan data
at once, but the I/O subsystem seems to split a big read call into
several 64k segments. Another problem is that the scanner expects
the READ_SCANNED_DATA SCSI command to have a number of scanlines
(not bytes) attached, so I will have to convert the number of
bytes from a read(2) call to a number of scan lines internally
in the driver code. My question is, if it is possible to read
in all the scan data at once from the scanner (wheter or not
it is handed to the user process in 64k segments). In other words,
I do want to only issue a READ_SCANNED_DATA SCSI command to the
scanner once, but not everytime a 64k segment is read by the user
process.

Thankful for any advice.

Rergards, Mickey

-- 
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          (@@)    Andreas S. Wetzel       Mail: mickey@deadline.snafu.de
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