umodem0, Cisco USB serial console, and quirks

[Ian Lepore]

On Sun, 2018-11-04 at 19:05 -0500, Mike Andrews wrote:
> On Fri, 2 Nov 2018, CeDeROM wrote:
> 
> > 
> > Try to add VID/PID of your device into a usbmodem driver. Use
> > configurations to see which one works with your device. Rebuild the
> > module/kernel, reboot, try it out untill success.
> > 
> > After your device is recognised by usbmodem and creates several cuaU*
> > devices.. still Your device may require uploading a specific firmware
> > in order for gsm modem to work. You can find those in Windows driver
> > package.
> > 
> > Use MINICOM for cuaU communications that would save you a debug time.
> > 
> > That works for me - added 3 devices like that with no problem. In fact
> > they work better on FreeBSD than Windows ;-)
> > 
> > 
> > Alternartively, replace your modem with something that is known to
> > work - for instance QUECTEL EC25 LTE module works far better than my
> > previous stock 3G module here..
> I think we're losing the plot here a bit.
> 
> While this is generally useful advice, this thread was originally about 
> the USB serial console port of Cisco ASA firewalls.  It should just be a 
> plain ol' USB-to-serial setup.  No actual modems of any kind involved, 
> especially not cellular ones.
> 
> I suspect we shouldn't even be loading umodem at all -- just ucom.  But 
> for some reason, umodem gets loaded when I plug the thing in.  With just 
> an FTDI serial-to-usb adapter in there, umodem doesn't just, just ucom.
> 
> These firewalls (and I suspect all of Cisco's newer routers and switches) 
> have both normal serial and mini-USB-to-serial ports, and you can connect 
> a simple USB-to-serial converter (PL2303, FTDI, etc) into the normal port 
> and of course that works fine on FreeBSD.  But it would be nice to skip 
> needing the dongle...

I'm curious whether the cisco side is truly a generic usb serial and
the problem is that the umodem driver is trying to do modem-specific
things which the cisco side is getting confused by.

A way to test that theory would be to add the cisco's vid/pid to the
ugensa driver (sys/dev/usb/serial/ugsena.c). If that works, I'm not
sure it's so much a solution as a clue.

I've always wanted a way to add VID/PID combos to ugsensa's internal
list on the fly, like via hints or sysctl or something, to make this
kind of quick test easier. But I never find time to add the feature.

-- Ian