[sane-devel] libusb vs linux kernel scanner driver

m. allan noah anoah@pfeiffer.edu
Fri, 11 Jul 2003 14:57:43 -0400 (EDT)

On Fri, 11 Jul 2003, Henning Meier-Geinitz wrote:

> Hi,
> On Fri, Jul 11, 2003 at 09:22:59AM -0400, m. allan noah wrote:
> > i am running usb fujitsu scanner on linux 2.4.21. the fujitsu backend uses 
> > sanei_usb, so both the kernel scanner driver, and libusb work. however, libusb 
> > causes a long pause, and a couple of timeouts happen, before the scanner starts. 
> > after that, the multi-page (adf) scans proceed normally, with no other errors.
> Do you see any timeout from the scanner driver in syslog? Maybe the
> timeout of the scanner driver is just shorter.

nope, timeouts only with the libusb connection.

 Usually a timeout
> occurs because of a bug in the backend (or hardware). But usually it's
> the other way round: the scanner driver tries longer to get some data
> than libusb.

no, the kernel driver starts the scan the second you ask, with no errors in the 
log, the libusb connection has a couple timeouts, and the scan starts after the 
timeouts are over, maybe 30 seconds. i am thinking that the logic in the kernel 
scanner driver and the libusb portions of sanei_usb must be sending different 
packets to the scanner, even though the backend does not distinguish between the 

> > so, it would seem to be lower level than the backend. anyone know how can i get 
> > more debugging info from the kernel scanner driver and libusb, so that i can see 
> > exactly what packets are going out to the device, and what sort of time 
> > signature they have?
> Not sure about libusb but to enable debugging in the scanner driver,
> edit linux/drivers/usb/scanner.h. There are two options: One for
> general debugging and one that enables pronting very USB packet.

cool, thanks. if i can get the scanner driver to dump all packets, and libusb to 
dump all, then i can compair.


> Bye,
>   Henning
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