[sane-devel] libusb vs linux kernel scanner driver

Henning Meier-Geinitz henning@meier-geinitz.de
Fri, 11 Jul 2003 17:38:43 +0200


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. 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.

> 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.