System hang (and other problems) with cdc_acm

[Thomas Tuttle]

Hi.

I've got a Lenovo X200 with an Ericsson F3507g Mobile Broadband Module
(a 3G cellular data card with built-in GPS), which uses the cdc_acm
driver.  I've experienced a couple of problems with it.  First, it
tends to hang the system after I've been using it for a while.  This
occurs whenever it's sending a lot of data to/from the computer,
whether it's a PPP connection or a GPS data stream.  I'm not sure how
to debug this; the Caps Lock light isn't flashing, so I'm not sure if
it's a panic or just a hang.  Second, if I read one of the TTYs using
"cat", I get a ton of blank lines.  To make any sense of the data
stream, I have to do cat /dev/ttyACM0 | grep -v "^$".

If anyone could help me debug this, I'd be greatly appreciative.

Thanks,

Thomas Tuttle
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