[sane-devel] Help needed diagnosing strange failure to scan with Samsung SCX-4500W

[ValdikSS]

On 07.05.2013 00:12, Mike Cloaked wrote:
> I have a strange scanner failure to try to resolve, and I am hoping that 
> an expert on this list may be able to help me fix the problem.
> 
> I have a Samsung SCX-4500W multifunction printer that is plugged in to 
> the usb port of my main machine running arch linux x86_64.  The printer 
> part works fine with the Splix driver, but the scanner fails to work.
> 
> When I unplug the device and plug it into a laptop running arch linux, 
> it works fine. On a second laptop also running arch linux the scanner 
> functions also work fine (xsane). However plugging the same device back 
> in to my main desktop the scanner fails to work.
> 
> 
> scanimage -L works the first time I issue the command but then 
> subsequently fails:
> 
> scanimage -L
> device `xerox_mfp:libusb:001:006' is a Samsung Samsung SCX-4500W Series 
> multi-function peripheral
> 
> scanimage -L
> 
> No scanners were identified.

Hello. I know this issue is 10 years old, but I fixed it.
It seems that this device has some bugs in USB stack implementation. I 
have SCX-4521F with the same issue, it works for me on one laptop with 
USB3 port (and only after explicit port reset!) but not on another with 
USB2.

It seems that the device hangs if ENDPOINT HALT CLEAR is performed on 
its out endpoint, which is explicitly sent by the backend.
If this command is not sent, the device works reliably.

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

Another workaround is to send CLEAR_TT_BUFFER command to the hub (which 
USB3 stack already does).

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