Hmm...seeing loads of these with strace:
openat(AT_FDCWD, "/dev/bus/usb/010", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 11
fstat(11, {st_mode=S_IFDIR|0755, st_size=60, ...}) = 0
getdents64(11, 0x18a0590 /* 3 entries */, 32768) = 72
openat(AT_FDCWD, "/dev/bus/usb/010/001", O_RDWR) = 12
ioctl(12, USBDEVFS_CONNECTINFO, 0x7ffff7c75018) = 0
read(12, "\22\1\20\3\t\0\3\tk\35\3\0\20\5\3\2\1\1", 18) = 18
read(12, "\t\2\37\0\1\1\0\340", 8) = 8
read(12, "\0\t\4\0\0\1\t\0\0\0\7\5\201\3\4\0\f\0060\0\0\2\0", 23) = 23
close(12) = 0
getdents64(11, 0x18a0590 /* 0 entries */, 32768) = 0
close(11) = 0
openat(AT_FDCWD, "/dev/bus/usb/010/001", O_RDWR) = 11
ioctl(11, USBDEVFS_IOCTL, 0x7ffff7c767e0) = 5
close(11) = 0
openat(AT_FDCWD, "/dev/bus/usb/009", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 11
fstat(11, {st_mode=S_IFDIR|0755, st_size=60, ...}) = 0
getdents64(11, 0x18a0590 /* 3 entries */, 32768) = 72
openat(AT_FDCWD, "/dev/bus/usb/009/001", O_RDWR) = 12
ioctl(12, USBDEVFS_CONNECTINFO, 0x7ffff7c75018) = 0
read(12, "\22\1\0\2\t\0\1@k\35\2\0\20\5\3\2\1\1", 18) = 18
read(12, "\t\2\31\0\1\1\0\340", 8) = 8
read(12, "\0\t\4\0\0\1\t\0\0\0\7\5\201\3\4\0\f", 17) = 17
close(12) = 0
getdents64(11, 0x18a0590 /* 0 entries */, 32768) = 0
close(11) = 0
openat(AT_FDCWD, "/dev/bus/usb/009/001", O_RDWR) = 11
ioctl(11, USBDEVFS_IOCTL, 0x7ffff7c767e0) = 3
close(11) = 0
openat(AT_FDCWD, "/dev/bus/usb/008", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 11
fstat(11, {st_mode=S_IFDIR|0755, st_size=100, ...}) = 0
getdents64(11, 0x18a0590 /* 5 entries */, 32768) = 120
openat(AT_FDCWD, "/dev/bus/usb/008/003", O_RDWR) = 12
ioctl(12, USBDEVFS_CONNECTINFO, 0x7ffff7c75018) = 0
read(12, "\22\1\0\3\t\0\3\t\t!\23\10\21\220\1\2\0\1", 18) = 18
read(12, "\t\2\37\0\1\1\0\340", 8) = 8
read(12, "\0\t\4\0\0\1\t\0\0\0\7\5\201\23\2\0\10\0060\0\0\2\0", 23) = 23
close(12) = 0
Guess I have too many USB devices connected....