Re: Configure a connection for a gsm with dynamic ttyACMx

[Jean-Christian de Rivaz <jc eclis ch>]

Le 29. 05. 15 00:53, Dan Williams a écrit :
> On Thu, 2015-05-28 at 22:28 +0200, Jean-Christian de Rivaz wrote:
> > Le 28. 05. 15 21:55, Dan Williams a écrit :
> > > On Thu, 2015-05-28 at 19:39 +0200, Jean-Christian de Rivaz wrote:
> > > > Le 26. 05. 15 19:24, Dan Williams a écrit :
> > > > > On Tue, 2015-05-26 at 19:04 +0200, Jean-Christian de Rivaz wrote:
> > > > > > Le 26. 05. 15 18:21, Dan Williams a écrit :
> > > > > > This is an alternative of the ENV(ID_MM_DEVICE_TAG_NAME) trick to get
> > > > > > the tag name. The fact that the name on D-Bus should be allowed to be
> > > > > > different from the dynamic tty is the main part that you also agree
> > > > > > on if I understand you correctly.
> > > > > Yes, I would prefer to do this without more tags, but using the normal
> > > > > symlink scheme that udev already supports well.  This also makes it
> > > > > non-ModemManager-specific since symlinks are often used for other
> > > > > programs as well.
> > > > Same question as in the ModemManager malling list:
> > > >
> > > > Just for curiosity, how did you plan to find the symbolic link that point to
> > > > the real ttyACMx ?
> > > g_udev_device_get_device_file_symlinks ()
> > Good catch, but in the ModemManager I explain why this will not solve
> > the problem for modem that expose multiple serial devices.
> Well, it would solve the problem, but it would mean writing udev rules
> that tag a particular modem port, and tagging control ports in MM like
> is done for other modems.

I agree with you: tagging is a more universal solution than symbolic 
links. From an user point of view writing a udev rule that set a 
variable is even simpler than writing a udev rule that create a symbolic 
link because the variable can have the same value for all the modem's 
serial devices while the link must be unique for each modem's serial 
device or must match a specific modem's serial device.

1) tag solution require a single udev rule for all the modem's serial 
devices and will contain:
ENV(ID_MM_DEVICE_TAG_NAME)="mymodem".

2) symlink solution require a udev rule for each modem's serial devices 
of to select the right serial device and will contain:
ENV{ID_USB_INTERFACE_NUM}=="xx", SYMLINK+="mymodem"

I seriously prefer the solution 1).

Jean-Christian