Powering off modems

Bjørn Mork bjorn at mork.no
Thu Feb 20 08:36:28 PST 2014

Dan Williams <dcbw at redhat.com> writes:
> On Thu, 2014-02-20 at 11:29 +0100, Aleksander Morgado wrote:
>> I was going to include CFUN=0 as default implementation, but didn't do
>> it. Maybe we should.
> The problem with this is when you tether a phone.  CFUN=0 tells the
> phone to turn off, which almost always is not what you want when you're
> just shutting down or suspending your laptop.  And it's typically hard
> to identify when something is a phone and when it's not, either through
> kernel drivers (most just show up as option or usbserial) or AT
> responses.

And it's not necessarily so that you want the modem to power down on
system suspend, even if it is not a phone. Sometimes it makes sense to
keep the modem powered even if the host is suspended.  You may not want
your IP sessions to go down just because you suspend the host.  And they
will if you power down the modem and don't have static addressing.

One of the few things that annoy me with my current Thinkpad is actually
that it seems impossible to keep the internal mini-PCIe slots powered
when suspending. The external USB ports can be kept powered, so external
modems can be kept active though.


More information about the ModemManager-devel mailing list