Solution:
If the kernel module update has been compiled then you can trouble shoot your installation by viewing the /var/log/messages file after loading the ftdi_sio module.
There are two reasons for failure:
1. Updated ftdi_sio module not compiled for pre 2.4.23 kernels.
2. ftdi_sio module was not loaded by the USB module.
If the ftdi_sio.c and .h files have not been compiled and the ftdi_sio module is not loaded then the USB module will not be able to identify the Perle USB serial adapter. The following example message will be displayed:
May 28 10:37:08 debian kernel: hub.c: USB new device connect on bus1/1, assigned device number 2
May 28 10:37:08 debian kernel: usb.c: USB device 2 (vend/prod 0x403/0xf0c0) is not claimed by any active driver.
If the updated files have been compiled correctly then the following messages will appear in your messages file:
Apr 23 10:20:55 rh9 kernel: usb.c: registered new driver serial
Apr 23 10:20:55 rh9 kernel: usbserial.c: USB Serial support registered for Generic
Apr 23 10:20:55 rh9 kernel: usbserial.c: USB Serial Driver core v1.4
Apr 23 10:20:55 rh9 kernel: usbserial.c: USB Serial support registered for FTDI SIO
Apr 23 10:20:55 rh9 kernel: usbserial.c: USB Serial support registered for FTDI 8U232AM Compatible
Apr 23 10:20:55 rh9 kernel: usbserial.c: USB Serial support registered for FTDI FT232BM Compatible
Apr 23 10:20:55 rh9 kernel: usbserial.c: FTDI FT232BM Compatible converter detected
Apr 23 10:20:55 rh9 kernel: usbserial.c: FTDI FT232BM Compatible converter now attached to ttyUSB0 (or usb/tts/0 for devfs)
Apr 23 10:20:55 rh9 kernel: usbserial.c: USB Serial support registered for USB-UIRT Infrared Receiver/Transmitter
Apr 23 10:20:55 rh9 kernel: usbserial.c: USB Serial support registered for Home-Electronics TIRA-1 IR Transceiver
Apr 23 10:20:55 rh9 kernel: ftdi_sio.c: v1.3.4:USB FTDI Serial Converters Driver
Note in some cases the USB module does not automatically load the ftdi_sio module. You can manually load it using the modprobe ftdi_sio command.
[root@rh9 root]# modprobe -r ftdi_sio
[root@rh9 root]# modprobe ftdi_sio
[root@rh9 root]# lsmod
Module Size Used by Not tainted
ftdi_sio 23352 0 (unused)
usbserial 22108 0 [ftdi_sio]
nls_iso8859-1 3516 1 (autoclean)
nls_cp437 5148 1 (autoclean)
vfat 13004 1 (autoclean)
fat 38808 0 (autoclean) [vfat]
ide-cd 35676 0 (autoclean)
cdrom 33728 0 (autoclean) [ide-cd]
lp 8996 0 (autoclean)
parport 37056 0 (autoclean) [lp]
autofs 13268 0 (autoclean) (unused)
e100 59652 1
keybdev 2976 0 (unused)
mousedev 5492 1
input 5888 0 [keybdev mousedev]
hid 11768 0 (unused)
usb-uhci 26188 0 (unused)
usbcore 83424 1 [ftdi_sio usbserial hid usb-uhci]
In this example the module was loaded and the Ultraport USB device was detected and allocated a tty device.
If the module load fails then you should perform a new module recompile.
Note: in some cases the USB connector cable may be forced into the USB port on the Ultraport unit upside down. This may generate an error message or no message in the messages file.