在 14.04 上，重启后第一次插入 Wacom 手写板时，它可以正常工作。这出现在 /var/log/syslog 中：
Oct 11 14:31:34 epicurus kernel: [122653.356109] usb 1-1.2: new full-speed USB device number 4 using ehci-pci
Oct 11 14:31:34 epicurus kernel: [122653.450885] usb 1-1.2: New USB device found, idVendor=056a, idProduct=00b8
Oct 11 14:31:34 epicurus kernel: [122653.450895] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=0
Oct 11 14:31:34 epicurus kernel: [122653.450900] usb 1-1.2: Product: PTK-440
Oct 11 14:31:34 epicurus kernel: [122653.450905] usb 1-1.2: Manufacturer: Tablet
Oct 11 14:31:34 epicurus mtp-probe: checking bus 1, device 4: "/sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2"
Oct 11 14:31:34 epicurus mtp-probe: bus: 1, device: 4 was not an MTP device
Oct 11 14:31:34 epicurus kernel: [122653.777615] input: Wacom Intuos4 4x6 as /devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2:1.0/input/input17
Oct 11 14:31:34 epicurus kernel: [122653.778439] usbcore: registered new interface driver wacom
Oct 11 14:31:34 epicurus kernel: [122653.858674] hidraw: raw HID events driver (C) Jiri Kosina
Oct 11 14:31:34 epicurus kernel: [122653.907632] usbcore: registered new interface driver usbhid
Oct 11 14:31:34 epicurus kernel: [122653.907635] usbhid: USB HID core driver
如果我拔下平板电脑的电源，然后重新插入，它就不起作用了。这次系统日志中只出现了以下几行：
Oct 11 15:11:19 epicurus kernel: [125025.451702] usb 1-1.2: new full-speed USB device number 9 using ehci-pci
Oct 11 15:11:19 epicurus kernel: [125025.546319] usb 1-1.2: New USB device found, idVendor=056a, idProduct=00b8
Oct 11 15:11:19 epicurus kernel: [125025.546329] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=0
Oct 11 15:11:19 epicurus kernel: [125025.546335] usb 1-1.2: Product: PTK-440
Oct 11 15:11:19 epicurus kernel: [125025.546340] usb 1-1.2: Manufacturer: Tablet
Oct 11 15:11:19 epicurus kernel: [125025.548353] input: Wacom Intuos4 4x6 as /devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2:1.0/input/input22
Oct 11 15:11:19 epicurus mtp-probe: checking bus 1, device 9: "/sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2"
Oct 11 15:11:19 epicurus mtp-probe: bus: 1, device: 9 was not an MTP device
我已尝试过rmmod wacom等等...但除了重新启动之外，没有任何方法可以使其恢复。
笔记：自从换了新的笔记本电脑和新的操作系统（Ubuntu 16.04）后，就不再遇到这个问题了 - 同一个平板电脑。