USB (GSM-)modems and ACM class driver

[Matthias Fuchs]

Hi,

I'm trying to get a Falcom Samba75 USB-GSM modem (similar to Siemens MC75)
to work under Linux 2.4.x. These modems are handled by the ACM class driver
and are working fine under 2.6 kernels but not under any 2.4.x kernel.

I've seen similar problems reported in some forums, also under FreeBSD systems.
Unfortunately I did not see any solution for this issue.

This is what I get in the kernel log:
..
acm.c: v0.21:USB Abstract Control Model driver for USB modems and ISDN adapters
hub.c: new USB device 00:15.0-1, assigned address 2
Manufacturer: Siemens AG Wireless Modules
Product: MC75
ttyACM0: USB ACM device
usb.c: USB disconnect on device 00:15.0-1 address 2
hub.c: new USB device 00:15.0-1, assigned address 3
Manufacturer: Siemens AG Wireless Modules
Product: MC75
ttyACM0: USB ACM device
usb.c: USB disconnect on device 00:15.0-1 address 3
hub.c: new USB device 00:15.0-1, assigned address 4
Manufacturer: Siemens AG Wireless Modules
Product: MC75
ttyACM0: USB ACM device
usb.c: USB disconnect on device 00:15.0-1 address 4


I know that 2.4 is not what this list really cares about. But at the moment
I have no chance to upgrade the target systems to 2.6.

If anybody has some information about what is going wrong under 2.4 with such
modems I would be glad here about that.

Matthias

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[Pete Zaitcev]

Post by Matthias Fuchs
hub.c: new USB device 00:15.0-1, assigned address 2
Manufacturer: Siemens AG Wireless Modules
Product: MC75
ttyACM0: USB ACM device
usb.c: USB disconnect on device 00:15.0-1 address 2

I don't know what it is. There's no usbmon for 2.4, so we cannot just
compare traces. Try to ramp up the printouts and see after what exact
command the modem disconnects.

-- Pete

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[Matthias Fuchs]

Hi,

even this issue is outstanding for about 8 weeks, I finally figured out a
work around.

Our investment into a Catalyst USB analyzer has been worthwhile.
While comparing the traces between 2.4 and 2.6 kernels, I found out that
the 2.4 kernels send two 'set configuration' requests to the USB modem.

Either this is not allowed or the modem's firmware does not like this.
After the 2nd set configuration request the device disconnects.

As a workaround, I just commented out the usb_set_configuration() call in
acm.c and thinks were fine with the Falcom Samba75 (aka Siemens MC75).

Matthias

Post by Pete Zaitcev

Post by Matthias Fuchs
hub.c: new USB device 00:15.0-1, assigned address 2
Manufacturer: Siemens AG Wireless Modules
Product: MC75
ttyACM0: USB ACM device
usb.c: USB disconnect on device 00:15.0-1 address 2

I don't know what it is. There's no usbmon for 2.4, so we cannot just
compare traces. Try to ramp up the printouts and see after what exact
command the modem disconnects.
-- Pete

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