I just picked up a new usb-rs232 adapter and was met by the following on
a modern kernel:

# uname -r
5.16.0-rc2

usb 3-7: new full-speed USB device number 5 using xhci_hcd
usb 3-7: New USB device found, idVendor=067b, idProduct=23a3, bcdDevice= 1.05
usb 3-7: New USB device strings: Mfr=1, Product=2, SerialNumber=0
usb 3-7: Product: ATEN USB to Serial Bridge
usb 3-7: Manufacturer: Prolific Technology Inc.
pl2303 3-7:1.0: pl2303 converter detected
pl2303 3-7:1.0: unknown device type, please report to linux-usb@vger.kernel.org


# lsusb -vv -d 067b:23a3

Bus 003 Device 005: ID 067b:23a3 Prolific Technology, Inc. ATEN USB to Serial Bridge
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            0 
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0        64
  idVendor           0x067b Prolific Technology, Inc.
  idProduct          0x23a3 
  bcdDevice            1.05
  iManufacturer           1 Prolific Technology Inc.
  iProduct                2 ATEN USB to Serial Bridge
  iSerial                 0 
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength       0x0027
    bNumInterfaces          1
    bConfigurationValue     1
    iConfiguration          0 
    bmAttributes         0xbf
      (Bus Powered)
      Remote Wakeup
      Battery Powered
    MaxPower              100mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           3
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      0 
      bInterfaceProtocol      0 
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x000a  1x 10 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x02  EP 2 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
can't get device qualifier: Resource temporarily unavailable
can't get debug descriptor: Resource temporarily unavailable
Device Status:     0x0000
  (Bus Powered)


But it worked on a bit older Debian Bullseye kernel:

# uname -r
5.10.0-8-amd64

usb 1-2: new full-speed USB device number 5 using xhci_hcd
usb 1-2: New USB device found, idVendor=067b, idProduct=23a3, bcdDevice= 1.05
usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=0
usb 1-2: Product: ATEN USB to Serial Bridge
usb 1-2: Manufacturer: Prolific Technology Inc.
usbcore: registered new interface driver usbserial_generic
usbserial: USB Serial support registered for generic
usbcore: registered new interface driver pl2303
usbserial: USB Serial support registered for pl2303
pl2303 1-2:1.0: pl2303 converter detected
usb 1-2: pl2303 converter now attached to ttyUSB0


I'm guessing it just needs a case for this bcdDevice.


//Anton