Scanning after printing fails with SXC-4200 over USB on Linux Fedora 38

[xR3Lc3bv]

Scanner is not working anymore after using the printer function on SXC-4200 over USB. Printer requires to be reconnected or rebooted.

Scanning applications using SANE time-out, scanimage:

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scanimage: open of device smfp:usb;04e8;341b;serialno. failed: Error during device I/O
Sometimes it works, however the scanner reacts slowly and sometimes needs several retries. The scanning fix, which seems to be reloading the usblp kernel module as is provided by suld-scanner-usblp-fix, is not reliable. Sometimes after minutes, it starts working again.

SCX-4200 firmare 1.13 V1.01.00 QDPL 1.40 11-14-2005
Using Fedora 38 X86_64, uld 1.00.39 from bchemnet.com. scanimage (sane-backends) 1.2.1; backend version 1.2.1 . Tried USB3 and USB2 port, no difference.

Kernel log shows the Samsung is going through several series of removing the device and reconnecting during scanning attempts, sometimes succeeding, most of the times not.

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2023-07-06T15:42:48,074502+03:00 usblp0: removed
2023-07-06T15:42:48,090429+03:00 usblp 1-3:1.1: usblp0: USB Bidirectional printer dev 55 if 1 alt 0 proto 2 vid 0x04E8 pid 0x341B
2023-07-06T15:42:50,295923+03:00 usblp0: removed
2023-07-06T15:42:50,310987+03:00 usblp 1-3:1.1: usblp0: USB Bidirectional printer dev 55 if 1 alt 0 proto 2 vid 0x04E8 pid 0x341B
2023-07-06T15:42:50,321085+03:00 usblp0: removed

Will try to test older driver versions, different distros, different hardware.

It is unclear if this is a problem with the device itself.

If anyone has any experiences please let us make a solution to share with all of us here.

[bchemnet]

Just a thought: have you tried a different USB cable?  Very occasionally a cable will start to fail and cause connect/disconnect cycles such as this.

Unfortunately I do not have any hardware I can use to provide further insight, but perhaps someone else does and will.

[ValdikSS]

This is initially a bug in USB implementation of the scanner which is triggered in xerox_mfp backend.
Since you're using smfp, try to disble xerox_mfp (comment it with # symbol) in /etc/sane.d/dll.conf.

You can also try to connect the device to USB3 port, sometimes it works better there.

https://gitlab.com/sane-project/backends/-/issues/706

Fix for xerox_mfp is on the way.