An example of the execution of dmesg in my machine: [ 145.124555] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 145.316324] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 145.504476] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 145.692368] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 145.885018] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 146.073539] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 146.260309] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 146.504290] usb 1-2: new high speed USB device using ehci_hcd and address 14 [ 146.572335] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 146.816163] usb 1-2: new high speed USB device using ehci_hcd and address 15 [ 146.885870] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 147.128051] usb 1-2: new high speed USB device using ehci_hcd and address 16 [ 147.196411] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 147.384813] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 147.572835] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 147.764365] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 147.960260] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 148.148459] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 148.336317] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 148.580468] usb 1-2: new high speed USB device using ehci_hcd and address 23 [ 148.648330] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 148.840731] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 149.028381] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 149.216901] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 149.408302] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 149.598199] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 149.852039] usb 1-2: new high speed USB device using ehci_hcd and address 29 [ 149.920227] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 150.164045] usb 1-2: new high speed USB device using ehci_hcd and address 30 [ 150.232263] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 150.420294] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 150.664288] usb 1-2: new high speed USB device using ehci_hcd and address 32 [ 150.732321] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 150.924355] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 151.113874] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 151.310523] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 151.500311] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 151.688318] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 151.888344] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 152.088365] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 152.277011] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 152.520074] usb 1-2: new high speed USB device using ehci_hcd and address 41 [ 152.588283] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 152.840162] usb 1-2: new high speed USB device using ehci_hcd and address 42 [ 152.908324] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 153.156661] usb 1-2: new high speed USB device using ehci_hcd and address 43 [ 153.224362] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 153.412394] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 153.664046] usb 1-2: new high speed USB device using ehci_hcd and address 45 [ 153.740923] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 153.984602] usb 1-2: new high speed USB device using ehci_hcd and address 46 [ 154.052205] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 154.240364] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 154.484041] usb 1-2: new high speed USB device using ehci_hcd and address 48 [ 154.552263] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 154.740308] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 154.928315] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 155.116338] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 155.304361] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 155.492381] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 155.680276] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 155.868300] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 156.112040] usb 1-2: new high speed USB device using ehci_hcd and address 56 [ 156.180327] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 156.368357] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 156.556382] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 156.804047] usb 1-2: new high speed USB device using ehci_hcd and address 59 [ 156.872285] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 157.060318] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 157.264341] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 157.452239] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 157.696058] usb 1-2: new high speed USB device using ehci_hcd and address 63 [ 157.764260] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 157.952294] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 158.140316] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 158.384068] usb 1-2: new high speed USB device using ehci_hcd and address 66 [ 158.452344] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 158.696616] usb 1-2: new high speed USB device using ehci_hcd and address 67 [ 158.766876] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 159.008033] usb 1-2: new high speed USB device using ehci_hcd and address 68 [ 159.077415] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 159.264325] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 159.452341] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 159.640362] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 159.828387] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 160.016281] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 160.261567] usb 1-2: new high speed USB device using ehci_hcd and address 74 [ 160.328314] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 160.572070] usb 1-2: new high speed USB device using ehci_hcd and address 75 [ 160.640351] hub 1-0:1.0: unable to enumerate USB device on port 2 [ 160.828377] hub 1-0:1.0: unable to enumerate USB device on port 2