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## 35. Why does my (Eaton 5E) USB UPS on Linux connect but quickly disconnects soon?

This issue was extensively investigated by NUT community members in https://github.com/networkupstools/nut/issues/630 and resulted in a chain of distribution bugs logged such as https://bugzilla.redhat.com/show_bug.cgi?id=1715504

The gist of it is that some versions of Linux kernel used an "USB HID quirk" for certain devices, see Linux kernel source `drivers/hid/hid-quirks.c` file, including MGE/Eaton vendor ID (0x0463) based on an older device a contributor had issues with. Firmware in newer devices no longer had the bug which needed the "quirk" and misbehaved when it was enabled. While newer (and much older) Linux kernels should not have the problem, with the quirk removed according to https://lkml.org/lkml/2018/11/26/580 having the issue in the field really depends on the combination of Linux kernel and device firmware that meet.

Either way, it seems that problematic combinations preclude Linux from seeing the device as a `hid-generic` first, to hand it over to a NUT driver.

This quirk can be tuned with a kernel boot parameter (via GRUB etc.):

    usbhid.quirks=0x0463:0xffff:0x08

to re-enable the NOGET quirk.

For context, according to https://bugzilla.redhat.com/show_bug.cgi?id=1875532 the symptoms for the problem look like this:

    # Plug in the UPS and observe the dmesg logs,
    # the following continuously appears:
    [   93.568082] usb 1-6: new full-speed USB device number 9 using xhci_hcd
    [   94.311469] usb 1-6: New USB device found, idVendor=0463, idProduct=ffff, bcdDevice= 0.01
    [   94.311475] usb 1-6: New USB device strings: Mfr=1, Product=2, SerialNumber=0
    [   94.311483] usb 1-6: Product: 5E
    [   94.311486] usb 1-6: Manufacturer: EATON
    [   96.269989] hid-generic 0003:0463:FFFF.000A: hiddev96,hidraw2: USB HID v1.10 Device [EATON 5E] on usb-0000:00:14.0-6/input0
    [  107.369425] hid-generic 0003:0463:FFFF.000A: usb_submit_urb(ctrl) failed: -1
    [  107.369469] hid-generic 0003:0463:FFFF.000A: timeout initializing reports
    [  112.828826] usb 1-6: USB disconnect, device number 9
    [  113.284452] usb 1-6: new full-speed USB device number 10 using xhci_hcd
    [  114.027693] usb 1-6: New USB device found, idVendor=0463, idProduct=ffff, bcdDevice= 0.01
    [  114.027698] usb 1-6: New USB device strings: Mfr=1, Product=2, SerialNumber=0
    [  114.027701] usb 1-6: Product: 5E
    [  114.027704] usb 1-6: Manufacturer: EATON
    [  115.984222] hid-generic 0003:0463:FFFF.000B: hiddev96,hidraw2: USB HID v1.10 Device [EATON 5E] on usb-0000:00:14.0-6/input0
    [  126.825756] hid-generic 0003:0463:FFFF.000B: usb_submit_urb(ctrl) failed: -1
    [  126.825775] hid-generic 0003:0463:FFFF.000B: timeout initializing reports
    [  132.527809] usb 1-6: USB disconnect, device number 10

A similar report on the driver side may look like:

    usbhid-ups[4554]: libusb_get_report: Input/output error
    upsd[4591]: Data for UPS [eaton] is stale - check driver
    usbhid-ups[4554]: Can't claim USB device [0463:ffff]: No such file or directory
    upsd[4591]: Can't connect to UPS [eaton] (usbhid-ups-eaton): No such file or directory
    upsmon[5148]: Poll UPS [eaton@localhost] failed - Driver not connected
    upsmon[5148]: Communications with UPS eaton@localhost lost

Other similar looking issues may include improper setup of udev, upower and similar frameworks to hand over the device from the OS to a driver daemon; competition with other software probing USB devices (ModemManager was mentioned in this context), including running several copies of the NUT drivers trying to use same port (e.g. one started by services and another manually as you tried to debug the problems).

Software quirks aside, please do test with a different USB cable and/or port on the computer. These were known to cause grief beyond what can be fixed with a few key words ;)

Finally, sometimes the issue is on the OS side (and/or USB chipset), to the point that the USB driver can not be unloaded and re-attached until you power cycle the system.

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