umodem0, Cisco USB serial console, and quirks

[Warner Losh]

On Fri, Nov 2, 2018 at 3:57 AM Hans Petter Selasky <hps at selasky.org> wrote:

> On 11/2/18 10:24 AM, Andrey V. Elsukov wrote:
> > On 02.11.2018 12:12, Hans Petter Selasky wrote:
> >>> # cu -l /dev/cuaU0
> >>> Connected
> >>>
> >>> <nothing here>
> >>>
> >>
> >> Did you try "-s" option to set another baudrate?
> >
> > Yes, the result is the same.
> >
> > # cu -s 115200 -l /dev/cuaU0
> > Connected
> >
> > If I understand correctly from
> >       https://www.bit0.com/tmp/usbmon-ciscoasa-verbose.txt
> >
> > The
> >
> > Leftover Capture Data: 80250000000008
> >
> > and
> >
> >   frame[1] WRITE 7 bytes
> >   0000  80 25 00 00 00 00 08 --  -- -- -- -- -- -- -- --  |.%.....
> >
> > is something like configuration data, where 80 25 is 0x2580 == 9600, so
> > it should work with default speed. When I use 115200, I see this:
> >
>
> All the commands for USB modems should be described here:
>
> https://www.usb.org/sites/default/files/CDC_EEM10.pdf
>
> I'm sorry, but I don't have time currently to decode the Linux traces
> and compare with FreeBSD.
>

One thing to also note about the Linux driver. "it just works" is only
because people have inserted a crap-ton of special cases and dealt with
weird quirks of different devices, and devices that are only kinda sorta
standards conforming, but easy enough to hack the driver to make work.
Chances are quite good you'll have to, as hps points out, puzzle through
the traces to find where it's non-conformant and/or our driver is
non-compliant.

Warner