Re: nmcli radio off connected to ModemManager power state low

[Carlo Lobrano <c lobrano gmail com>]

Hello Dan,

thank you, it is more clear now. I will check in my system for rfkill.

One more question, do you think it will be feasible for NM to check whether rfkill is available and, if not, to set the modem in power off in place of just disabling it?

Carlo

On Fri, 11 Mar 2016 at 17:18 Dan Williams <dcbw redhat com> wrote:

On Fri, 2016-03-11 at 14:49 +0100, Carlo Lobrano wrote:
> Hello everybody,
>
> making some changes in ModemManager "set power state", I observed
> that setting
> setting a radio interface to OFF with nmcli, the ModemManager power
> state
> triggered is the LOW one, while I expected it to be the OFF one. Is
> that
> correct? If that so, is there a way to set the modem in OFF power
> state
> through network manager?

There are two things that 'nmcli r wwan off' does:

1) attempts to set any kernel rfkill WWAN switches to "blocked"
2) disables the modem with ModemManager, which sets low power state

If your kernel/hardware has rfkill capability then the modem will
actually be completely killed and off, and will often drop off the USB
bus too.

But if your kernel/hardware doesn't have rfkill, NM skips the rfkill
step and asks ModemManager to put the modem into low-power mode.
 Without rfkill capability if the modem/phone powers off completely
(which some do with CFUN=0), there's no way to get the modem turned
back on with 'nmcli r wwan on' because the modem has either completely
disappeared, or isn't responding to commands (because it's off).

So I looked through my collection and out of the 20 USB modems I tried,
only two actually powered off with CFUN=0; Nokia 21M-02 and Ericsson
MD300.  The rest stayed up and running, so obviously it would be
possible to use CFUN=0 (or equivalent) on most devices.

But is there a huge power draw difference between CFUN=0 and CFUN=4 in
most devices?  If there isn't, I'd prefer CFUN=4, and typically an
rfkill-setup is more useful for complete power off than CFUN=0 since
that also kills any USB power draw too.

Dan