Re: ZTE modem problems and workrounds

[Rick Jones <rick activeservice co uk>]

--On Monday, July 06, 2009 13:53:01 -0400 Dan Williams <dcbw redhat com> wrote:

> On Fri, 2009-07-03 at 17:27 +0200, Alexander Sack wrote:
> > On Fri, Jul 03, 2009 at 04:19:30PM +0100, Rick Jones wrote:
> > > 
> > > The fix was already picked up on launchpad, so I installed the new build. It
> > > always picks up the correct port - good - but something's broken when trying to
> > > make a connection.
> > 
> > I see a (most likely the same) regression with yesterdays 0.7 branch
> > builds for my option card; ppp hangs up quickly like this:
> 
> Should be fixed by
> http://cgit.freedesktop.org/NetworkManager/NetworkManager/commit/?h=NETWORKMANAGER_0_7&id=364ab2f86d6ebdf9552b7cc6b197b2c76ea3b8aa

Looks good, it's now only ever using IF3.

I find that about one time in 4 or 5 it doesn't detect any port as a modem, but unplug/re-plug and it usually gets it. I think this is probably because the probe responses get masked by the stream of UMs coming out (+ZUSIMR:2), these need to be killed off by sending +CPMS?. This has to be done anyway to get the thing to dial reliably - I rely on an external script to do it at the moment, but it's not ideal. Would it be feasible for nm-modem-probe to do this?

There is another problem with the serial port termios modes, AFAICT, NM doesn't set them up, but neither does the Option driver. They can have an arbitrary state which results in unpredictable behaviour, and even kernel panics.

I've tried a patch to the option module which initialises them to the equivalent of "stty raw", and this makes things much more stable. I don't think the driver is the right place to do this though (it was just easiest to tweak), the program opening the port should set them as required. Seeing that they are sticky once set, and should be set as early as possible, it seems that nm-modem-probe would also be the place to do this. What do you think?

Rick