[sane-devel] HP Scanjet 3P io errors

abel deuring a.deuring@satzbau-gmbh.de
Sun, 22 Jun 2003 22:25:13 +0200

jd wrote:
> I found nothing related in the archives:

It' s a bit difficult to find ;) I needed a few minutes to search 
through my private mail archive to find the the answer.

> Using sane front & back ends v1.0.7
> Device is Scanjet 3P and ADF, model 2570A, firmware 3430.
> Connected to Buslogic BT946C.
> sane does not seem to like my scanner. It returns io device errors.
> Works fine with epson scanner.

In short: The combination Buslogic driver/Linux kernel 2.4/HP scanner 
does not work well.

The longer explanation: For certain commands, the HP backend cannot 
predict the exact size of a data block returned for a certain SCSI 
command. If the scanner return less or more data than "declared" by the 
backend, the Buslogic driver raises an error and does not return any data.

This data underrun/overrun is not an issue for most other scanners -- in 
general, the Sane backends can precisely predict the length of tha sent 
to/received from the scanner.

The short conclusion: Use another SCSI adapter for the HP scanner. The 
longer conclusion: The Buslogic driver would need a new maintainer, who 
can continue the work of the late Leonard Zubkoff.