How to log USB modem data for a specific device?

[Greg KH]

On Mon, Nov 11, 2019 at 11:40:51AM -0500, Jeffrey Walton wrote:
> On Mon, Nov 11, 2019 at 11:31 AM Greg KH <greg at kroah.com> wrote:
> >
> > On Mon, Nov 11, 2019 at 11:11:06AM -0500, Jeffrey Walton wrote:
> > > Hi Everyone,
> > >
> > > I'm having trouble with a C application that opens a USB modem. The
> > > application is not receiving some data from a USR modem. Conexant
> > > modems are OK.
> > >
> > > I'm working through
> > > https://www.kernel.org/doc/Documentation/usb/usbmon.txt . I found the
> > > modem at Bus=01 Dev=24:
> > >
> > > T:  Bus=01 Lev=03 Prnt=07 Port=00 Cnt=01 Dev#= 24 Spd=480  MxCh= 0
> > > D:  Ver= 2.00 Cls=02(comm.) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
> > > P:  Vendor=0baf ProdID=0303 Rev= 2.00
> > > S:  Manufacturer=U.S.Robotics
> > > S:  Product=USB Modem
> > >
> > > This is where my confusion lies. It is not clear to me how to
> > > determine which socket to use for step #3 in usbmon.txt. Step #3 says:
> > >
> > >    # cat /sys/kernel/debug/usb/usbmon/3u > /tmp/1.mon.out
> > >
> > > How do I determine which socket to use for Bus=01 Dev=24?
> >
> > From the above documentation, it says to use "3u" for all devices on the
> > 3rd bus.  You want the 1st bus, right?  So did you try using "1u"?
> >
> > I think wireshark can intrepret usbmon output, so maybe just use that
> > instead and point it at the USB bus you want to watch?
> 
> Thanks Greg.
> 
> I want Bus 1, but I want Device 24 (not all devices).

That's not what usbmon will show.  Look at wireshark and see if it can
filter the output for just that one device.

There's also the old-style USB device snoop interface, that works on a
per-device level.

good luck!

greg k-h