reset full-speed usb device number

[Sebastian Schauenburg]

On Ubuntu MATE 17.10 (artful) I found this bug when I tried to get my DPF LCD screen (connected via USB) working. I also tested my Ubuntu 17.10 MATE laptop install and I get the same result, so it is not a hardware issue. On my Debian stretch laptop, it works just fine.

When I run 'lcd4linux -Fvvv' it fails with:
lcd4linux.c: initializing driver DPF
dpf_ax_open: found AX206 #1
dpf_ax_open: no matching USB device 'usb0' found!
dpf: cannot open dpf device usb0
Error initializing driver DPF: Exit!

meanwhile I can see the following in syslog:
Nov 3 16:40:31 prometheus kernel: [73114.705716] usb 3-12.2: reset full-speed USB device number 88 using xhci_hcd
Nov 3 16:40:31 prometheus kernel: [73114.835220] usb 3-12.2: USB disconnect, device number 88
Nov 3 16:40:31 prometheus kernel: [73114.929498] usb 3-12.2: new full-speed USB device number 89 using xhci_hcd
Nov 3 16:40:31 prometheus kernel: [73115.067057] usb 3-12.2: New USB device found, idVendor=1908, idProduct=0102
Nov 3 16:40:31 prometheus kernel: [73115.067061] usb 3-12.2: New USB device strings: Mfr=2, Product=3, SerialNumber=1
Nov 3 16:40:31 prometheus kernel: [73115.067062] usb 3-12.2: Product: USB-Display
Nov 3 16:40:31 prometheus kernel: [73115.067064] usb 3-12.2: Manufacturer: hackfin
Nov 3 16:40:31 prometheus kernel: [73115.067065] usb 3-12.2: SerialNumber: 002
Nov 3 16:40:31 prometheus mtp-probe: checking bus 3, device 89: "/sys/devices/pci0000:00/0000:00:14.0/usb3/3-12/3-12.2"
Nov 3 16:40:31 prometheus mtp-probe: bus: 3, device: 89 was not an MTP device

Somehow a USB reset is triggered, which disconnects and reconnects the LCD screen, which in turn causes the device not to be found, since the USB ID is incremented.

[Sebastian Schauenburg (sschauenburg)]

Apparently this happens when /tmp does not have exec. Remounting /tmp with exec provides a workaround.