How to log USB modem data for a specific device?

[Jeffrey Walton]

On Tue, Nov 12, 2019 at 12:37 AM Greg KH <greg at kroah.com> wrote:
> ...
>
> > Here's why I want to specify a device number:
> >
> >     $ cat /sys/kernel/debug/usb/devices | grep -i -c 'Bus=01'
> >     13
> >
> > It is too much information for me to sift through. I'll do it if I
> > have to, but I prefer the tools do the work for me (rather than me do
> > the work of the tools).
>
> That explains why you only want one device's data, but does not answer
> why you want that data at all :)

I have a pet project like NoMoRobo. It is essentially a call blocking
service that depends on Caller ID. My pet project takes things a step
further by initiating a call trace on suspicious numbers, and also
files FCC and FTC complaints.

The program works well with Conexant, Accura/Hayes and MultiTech
modems. The program chokes on USR modems. For USR I get the RING
message, but not the Caller ID information. From my program's
perspective, it looks like the Caller ID information is never sent.

So I want to perform some low level traces to understand why I am
mishandling things.

The GNU screen program receives the information as expected. The
problem is, GNU screen does not show me individual messages. I don't
know where one message ends and another begins. (One of my theories is
the USR modem is batching RING and Caller ID into a single message).

Jeff