I am experiencing the same issue with a Canon 9000F scanner: when I switch the scanner off then back on, scanbd fails to reconnect to it. The error message is identical (mutans mutatis) to that in the logs posted here, but in my case `scanimage -L` shows that the device name has not changed.
Nonetheless, sane is still returning SANE_STATUS_INVAL.
I have turned on debug output in scanbd, and looked at the source code, but I can't see why the call to sane_open is succeeding the first time, but not subsequently. It might be worth debugging inside libsane to make progress, but I'd welcome assistance from experts!
For now, I added an rsyslog filter that runs a program to restart scanbd whenever it logs an "abandon" message.
This in itself requires a few steps:
1. Compile the following C program, setuid, as /usr/local/sbin/restart-scanbd:
#include <stdlib.h>
int main (void)
{
system ("sudo systemctl restart scanbd.service");
}
2. Write the rsyslog filter to execute it (/etc/rsyslog.d/99-scanbd):
:msg, regex, "/usr/sbin/scanbd: abandon polling of" ^/usr/local/sbin/restart-scanbd
3. Edit systemd's unit for rsyslog to add "NotifyAccess=all" (sudo systemctl edit rsyslog), otherwise the filter doesn't get executed.
4. Run visudo and add the following to /etc/sudoers:
# Allow syslog to restart scanbd
syslog ALL=(root) NOPASSWD: /usr/bin/systemctl restart scanbd.service
It's a painful workaround, but for me it worked flawlessly.
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