On 01/14/2021 12:58 PM, Stephen John Smoogen wrote:
On Thu, 14 Jan 2021 at 12:19, Fred fred.fredex@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@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
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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.