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I have recently installed Xubuntu 14.04 on two computers. Computer A is a DELL Aptitude E5430 laptop, whereas Computer B is a home-mounted desktop, with an ASUS H87-Plus motherboard. I have been trying to make an EPSON Perfection V33 scanner work with both computers, with mixed results.

First of all, I downloaded the appropriate programs from the Epson site and installed all three of them on both computers.

My DELL has 4 USB connectors: one at the right-hand side (USB2), one at the back (USB2) and two at the left-hand side (one USB2 and one USB3). If I plug the scanner into the connector at the right-hand side, I can run Image Scan! and Simple Scan without any problem. However, if I use either one of the other two USB2 connectors, the problems start: the sane-find-scanner utility finds and identifies the scanner; and scanimage -L works OK as well; but when I try to run Image Scan! the scanner produces the customary humming noises, the ON lamp blinks for a few seconds, but the Image Scan! screen never appears, and after a while the program disconnects and sends the following message:

Could not send command to scanner. Check the scanner's status.

If I run Simple Scan, the initial screen appears, but I cannot make it scan anything.

It turns out that when I plug the scanner into connector 1, the Linux kernel assigns ehci-pci to it; when I use connectors 2 or 3 it assigns xhci_hcd. I have no idea why this happens. Anyway, I think it explains why scanning cannot occur when connectors 2 or 3 are used, because the Epson drivers for this scanner are known to be incompatible with USB3.

To confirm this, I then plugged the scanner into one of the USB2 connectors of computer B (the ASUS desktop). As with my laptop, sane-find-scanner and scanimage -L showed no problem. But, sure enough, xhci_hcd was assigned to the scanner, and scanning failed, despite the humming and blinking. I then disabled USB3 via BIOS; this time ehci-pci was assigned to the scanner, and scanning proceeded normally.

I want to keep the scanner plugged to the ASUS desktop in my office, but disabling USB3 on this computer every time I need to scan is obviously inconvenient. So here is my question: could I make the kernel assign ehci-pci to the scanner instead of xhci_hcd (maybe through a udev rule)? So far I have been unable to find a clear answer or a good solution, so any help will be appreciated.

Many thanks in advance.

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