[sane-devel] Problems with libusb and Snapscan 1236U (maybe similar to others): USB dump

Henning Meier-Geinitz henning@meier-geinitz.de
Mon, 1 Mar 2004 18:25:02 +0100


On Mon, Mar 01, 2004 at 11:46:58AM -0500, m. allan noah wrote:
> if that works, then perhaps there is a libusb/linux kernel error that 
> prevents the DATA0/1 toggle from frobbing.

IIRC that's a bug in some USB chipsets. It happens when the connection
is resetted (?). The USB spec says that in this case the toggle should
be set to 0. Linux does that but some USB chips (e.g. Mustek 1017)
doesn't. So everytime the connection is reset with toggle = data1 the
communication fails. With libusb this happens after every close. With
the kernel scanner driver only when the module is unloaded. On *BSD
it also happens with every close().

So it may not be a bug in the kernel.