On Sun, Jun 27, 2021 at 09:24:45PM -0400, Matt Corallo wrote: > > > On 6/27/21 21:16, Alan Stern wrote: > > You mean that only devices in the first group are affected by this bug? > > Devices in the second group are always detected correctly regardless of > > what else is plugged in? (This contradicts what you wrote above.) > > > Correct. Ignoring hotplug (ie on fresh boot or lsusb -vvv), the devices in > the second group work great. The devices in the first group do too, but only > if a device from the second group is present. Okay. You can try collecting some usbmon traces to see what's going on. First test: Boot with nothing plugged in, start a usbmon trace for bus 0 (cat /sys/kernel/debug/usb/usbmon/0u >mon1.txt), plug in a first-group device, run lsusb -v to trigger enumeration, and then kill the "cat" process. Second test: Same as the first except that you boot with a second-group device already plugged in. The differences between the two traces may indicate where the problem is. Alan Stern
