On Tue, Mar 01, 2011 at 04:41:56PM +0000, Simon Leung wrote:

On 01/03/11 16:37, Greg KH wrote:

quoted

On Tue, Mar 01, 2011 at 04:10:43PM +0000, Simon Leung wrote:

quoted

Hi all,

I'm having a problem with my 3G USB stick (Huawei E220) .

The kernel I'm using is version 2.6.21 customized for an ARM board. When
I insert the USB stick into the system, normally 3 device show up:
/dev/ttyUSB{0,1,2}. The problem I' having is that some time, only the
first one shows up and I cannot connect to it. When this happens,
normally a reboot will fix it.

As I said, this sounds like a kernel/driver issue to me. Could somebody
give me some pointers as how to prove/fix it?

As you are stuck with an obsolete kernel version, please get support
from the vendor of that kernel, it is very old and we can't do much, if
anything, about it :(

Can you duplicate this problem on a modern kernel (like one released in
the past year?)

thanks,

greg k-h

I know. I probably can (and probably will) upgrade the kernel and the 
problem will probably go away. But I'd like to take the opportunity and 
hopefully learn something. Even knowing which part of the kernel is  
handling the usb serial device is fine.

The part is in drivers/usb/serial/ and it depends on the actual device
you are using, and the host controller you are using.

I place the odds on your host controller being the problem, for what
it's worth, especially on older ARM kernels like you are stuck with.

Best of luck,

greg k-h