[sane-devel] Is the Iscan backend "epkowa" also affected by USB3 issues?

Olaf Meeuwissen olaf.meeuwissen at avasys.jp
Wed Apr 27 23:45:48 UTC 2016

Hi Johannes,

I'll forward your question as I am no longer doing any scanner work at
the office (as of the end of March 2016).  As we are just one day away
from Golden Week[1], it will probably take a while before you get an
answer (if at all).  I think people will only get back to the office 
on 2016-05-09.

 [1] https://en.wikipedia.org/wiki/Golden_Week_(Japan)

OK, now on to your question,

Johannes Meixner writes:

> [...]
> Now I wonder if the "epkowa" backend could be also affected by the
> current sane-backends 1.0.25 "Workaround for USB3 problems in Linux
> kernel" that seems to no longer work with newest kernels, cf.
> http://lists.alioth.debian.org/pipermail/sane-devel/2016-January/034254.html
> In other words, I wonder if the "epkowa" backend uses the
> sane-backends USB code or if the "epkowa" backend implements USB
> communication on its own.

The epkowa backend uses its own *copy* of the sanei_usb code.  There was
a minor fix for USB 3.0 connected scanners in 2.30.1 (dated 2014-12-03).
That same fix was applied to sane-backends on 2014-12-10.

Please note that iscan does *not* actively track changes to the
sane-backends version of the sanei_usb code.  Also, iscan-2.30.1 is the
most recent version.

> In the end I like to understand if a version change of the installed
> sane-backends software on the user's computer could make a difference
> whether or not the "epkowa" backend works with the xhci_hcd kernel
> module.

That is rather unlikely but not impossible as it may depend on what
other backends do during their sane_init() and sane_get_devices().  If
all other backends are disabled, changing the version of the installed
sane-backends should not make a difference.  That is because the dll
backend doesn't do anything USB related itself.

Hope this helps,
Olaf Meeuwissen, LPIC-2       FLOSS Engineer -- EPSON AVASYS CORPORATION
       Free Software Foundation Associate Member since 2004-01-27
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