voilà ce que j'obtiens en déconnectant reconnectant:
May 5 20:20:46 raspberrypi kernel: [ 202.270605] usb 1-1.2: USB disconnect, device number 4
May 5 20:20:46 raspberrypi kernel: [ 202.276833] ftdi_sio ttyUSB0: FTDI USB Serial Device converter now disconnected from ttyUSB0
May 5 20:20:46 raspberrypi kernel: [ 202.277191] ftdi_sio 1-1.2:1.0: device disconnected
May 5 20:21:14 raspberrypi kernel: [ 229.700414] usb 1-1.2: new full-speed USB device number 7 using dwc_otg
May 5 20:21:14 raspberrypi kernel: [ 230.076845] usb 1-1.2: New USB device found, idVendor=0403, idProduct=6001, bcdDevice= 6.00
May 5 20:21:14 raspberrypi kernel: [ 230.076880] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
May 5 20:21:14 raspberrypi kernel: [ 230.076892] usb 1-1.2: Product: USB-COM232 Plus1
May 5 20:21:14 raspberrypi kernel: [ 230.076948] usb 1-1.2: Manufacturer: FTDI
May 5 20:21:14 raspberrypi kernel: [ 230.076963] usb 1-1.2: SerialNumber: FT4606O7
May 5 20:21:14 raspberrypi kernel: [ 230.102225] ftdi_sio 1-1.2:1.0: FTDI USB Serial Device converter detected
May 5 20:21:14 raspberrypi kernel: [ 230.102604] usb 1-1.2: Detected FT232RL
May 5 20:21:14 raspberrypi kernel: [ 230.104377] usb 1-1.2: FTDI USB Serial Device converter now attached to ttyUSB0
May 5 20:21:14 raspberrypi mtp-probe: checking bus 1, device 7: "/sys/devices/platform/soc/20980000.usb/usb1/1-1/1-1.2"
May 5 20:21:14 raspberrypi mtp-probe: bus: 1, device: 7 was not an MTP device
May 5 20:21:15 raspberrypi mtp-probe: checking bus 1, device 7: "/sys/devices/platform/soc/20980000.usb/usb1/1-1/1-1.2"
May 5 20:21:15 raspberrypi mtp-probe: bus: 1, device: 7 was not an MTP device
May 5 20:21:19 raspberrypi kernel: [ 234.970722] Voltage normalised (0x00000000)