On 01/14/2021 12:58 PM, Stephen John Smoogen wrote: > On Thu, 14 Jan 2021 at 12:19, Fred <fred.fredex at gmail.com> wrote: > >> from a non-expert (me): >> >> possibly figure out what happens when the device is plugged/unplugged and >> doing that by hand. if you can find the udev file(s) that manage the >> port(s) that get hung you may be able to figure out what those steps would >> be. >> >> or you could try, when hung, plugging it into a different USB port... some >> motherboards have multiple USB controllers, so even if one gets wedged >> tight, the other one(s) shouldn't be. >> >> > So what can happen is that the USB device is seeing a lot of noise from the > interface and shutdown the interface for a period of time. If you are > extremely lucky, it will even send some sort of message to the computer bus > it is doing this. In most other cases, the only fix is to reboot or > temporarily unplug the devices connected to that particular USB controller > (a computer may have multiple USB controllers since USB is a hubbed network > and collisions and conflicts are expected for short periods.). [It used to > be that you could cause a USB reset by removing the modules from the kernel > and add them but that was a long time ago when a PS/2 keyboard was a real > device and not an emulated PS/2 connected to the USB hub. ] > > > > > >> Good Luck! >> >> Fred >> >> On Thu, Jan 14, 2021 at 11:22 AM Frank Bures <listfrank1 at gmail.com> wrote: >> >>> Hi, >>> >>> my USB connected printer goes into deep space from time to time probably >>> due to a HW problem on the MoBo. >>> >>> Is there a way how to reset the USB subsystem the same way one can >> restart >>> networking or X without the necessity to reboot? >>> >>> Thanks >>> Frank >>> >>> -- >>> >>> <listfrank1 at gmail.com> >>> _______________________________________________ >>> CentOS mailing list >>> CentOS at centos.org >>> https://lists.centos.org/mailman/listinfo/centos >>> >> _______________________________________________ >> CentOS mailing list >> CentOS at centos.org >> https://lists.centos.org/mailman/listinfo/centos >> > A few months ago I reported that I could not get a Logitech C922 ProStream video camera working on my Lenovo Thinkstation running CentOS 7. The BIOS was updated and the motherboard was replaced to no avail. I could then confirm that the camera worked fine if I booted Ubuntu Live, hence no hardware issue with the computer, nor the camera which by the way worked fine on a laptop also running CentOS 7. Since the USB subsystem did not recognize the camera when plugged in I reported this as a kernel/USB subsystem bug to RedHat. For some reason they made the bug private and I have not heard any more about it being worked on... Howewer, two or so weeks ago I stumbled across https://zedt.eu/tech/linux/restarting-usb-subsystem-centos/ and used this procedure to reset the USB subsystem. This gets the camera working - most of the time... The OP may want to try the same thing.