MicroHam USBII Linux driver hacking for kernel 2.6.xxx
======================================================

Sun Sep 16 20:27:24 CEST 2007
Jaakko Koivuniemi OH7BF


Problem: the default ftdi_sio driver did not recognize the microHam USBII
interface. In addition the driver was setting DTR and RTS high, which keys
the radio after the driver is loaded.

Warning: Modifying the driver code probably breaks it for other USB serial 
converters using the same chip. Kernel drivers have also a lot of freedom to 
damage your system and hardware, so do the modifications at your own risk. 

Hacking is not the right way to solve the problem, but this worked for me:

1) Kernel headers need to be present to compile the modules. Get the files

ftdi_sio.c 
ftdi_sio.h 
usb-serial.c 
usb-serial.h

from kernel source directory.

2) The files 'ftdi_sio.h' and 'ftdi_sio.c' need to be modified. 

In 'ftdi_sio.h' change the line

#define FTDI_8U232AM_PID 0x6001 /* Similar device to SIO above */

to

#define FTDI_8U232AM_PID 0xEEEF /* Similar device to SIO above */

In 'ftdi_sio.c' the following lines

 /*    /\* Turn on RTS and DTR since we are not flow controlling by default *\/ */
< /*    if (set_dtr(port, HIGH) < 0) { */
< /*            err("%s Error from DTR HIGH urb", __FUNCTION__); */
< /*    } */
< /*    if (set_rts(port, HIGH) < 0){ */
< /*            err("%s Error from RTS HIGH urb", __FUNCTION__); */
< /*    } */

are changed to 

<        /* Change the code below to keep RTS and DTR low 
<           -- Jaakko, Thu Feb 23 00:29:04 CET 2006 */
<       if (set_dtr(port, LOW) < 0) {
<         err("%s Error from DTR LOW urb", __FUNCTION__);
<       }
<       if (set_rts(port, LOW) < 0){
<         err("%s Error from RTS LOW urb", __FUNCTION__);
<       }

3) Create make file to build the 'ftdi_sio.ko' module:

obj-m += ftdi_sio.o

all:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

4) Copy the files to same directory, for example 

ftdi_sio_ham/ftdi_sio.c 
ftdi_sio_ham/ftdi_sio.h 
ftdi_sio_ham/usb-serial.c 
ftdi_sio_ham/usb-serial.h
ftdi_sio_ham/Makefile

5) Run 'make'

6) Take copy of the original ftdi_sio.ko kernel module

cd  /lib/modules/2.6.xxx/kernel/drivers/usb/serial/
cp ftdi_sio.ko ftdi_sio.ko.orig

7) Copy the kernel module to /lib/modules, for example

cd ftdi_sio_ham

cp ftdi_sio.ko /lib/modules/2.6.xxx/kernel/drivers/usb/serial/

8) Load the modules

/sbin/insmod /lib/modules/2.6.xxx/kernel/drivers/usb/serial/usbserial.ko

/sbin/insmod /lib/modules/2.6.xxx/kernel/drivers/usb/serial/ftdi_sio.ko 

9) Check that the new ftdi_sio module recognizes the USBII by powering the
interface first from radio side and then connecting the USB cable to PC 
while monitoring the kernel log

tail -f /var/log/messages

10) In kernels 2.6.xxx there is no need to create /dev/ttyUSBx anymore, 
it is created automatically when the module is loaded. Now you should find

ls -l /dev/ttyUSB0

crw-rw----  1 root uucp 188, 0 May 29 23:00 /dev/ttyUSB0

Add your login name to the uucp group.

usermod -a -G uucp mylogin

11) Renaming the ftd_sio.ko module is probably a good idea. This should 
allow to use the original driver in parallel.