[sane-devel] R: Re: R: Re: scanner Epson DX4250 not working in Ubuntu 11.10

Olaf Meeuwissen olaf.meeuwissen at avasys.jp
Thu Apr 26 23:01:24 UTC 2012

Richard Ryniker <ryniker at alum.mit.edu> writes:

>>Now it is guess work why the device is temporarily unavailable when
>>trying to reset it, but replies just fine to the status query to comes
>>immediately after.
> Timing issue?  Perhaps the two bytes written to the device start some
> action that has not completed before the read request is tried,
> therefore the "Resource temporarily unavailable" status.

The two bytes written to the device cause a reset.  All that needs to be
done is initializing a limited number of values in the firmware, nothing
that takes a significant about of time.

> If the read operation is retried, it might succeed.

That's something the backend should be doing to begin with when this
particular condition happens during USB I/O but the sanei_usb wrapper
merely returns SANE_STATUS_IO_ERROR so there no way you can tell what
went wrong.  For all the backend knows the USB might have been pulled
or the device could have been turned off.

Hope this helps,
Olaf Meeuwissen, LPIC-2           FLOSS Engineer -- AVASYS CORPORATION
FSF Associate Member #1962               Help support software freedom

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