Re: NetworkManager and rf_kill

[Tony Espy <espy canonical com>]

Dan Williams wrote:
> On Mon, 2008-05-12 at 17:46 +0200, Khashayar Naderehvandi wrote:
> > I really might be misunderstanding something here, but deactivating
> > wireless through nm-applet should in fact (as things are currently
> > with NM from svn), do a ifconfig wlan0 down? Is this correct? Because
> > doing that manually, my wifi doesn't suck battery power anymore.
> > However, nm-applet seems to take down the wireless device _only_ when
> > I deactivate network completely, that is, when I deactivate wireless,
> > wired and GSM capabilities. Only deactivating wireless leaves the
> > device up, and hence reduces uptime on battery.
>
> We do need to mark the device down when it's disabled; that somehow went
> away when rewriting the device state handling.  Should be a pretty easy
> fix in nm-device-802-11-wireless.c::nm_device_802_11_wireless_set_enabled().
>
> I was going to change that code to set the TX power of the card off
> instead of taking it down, because some hardware (iwl3945) needs
> firmware loaded to notice rfkill changes, and setting the device down
> unloads the firmware.  So at least on some devices you need to always
> keep the card up.  But HAL isn't smart enough yet to distinguish between
> soft rfkill and hard rfkill, so setting TX power off, to HAL, looks just
> like a hard rfkill and you can't turn the rf back on in software :(
> That's a fairly easy patch to HAL though.

I've been following this thread with interest because I've recently 
implemented this feature on top of network-manager-0.6.6~rc2 ( the 
version in Ubuntu 8.04 ) as part of some custom Ubuntu Mobile work.

I added logic to invoke the Hal KillSwitch::SetPower method from within 
the wireless_set_enabled() function.  I also added a sw_rf_enabled flag 
to handle allowing the user to re-enable wireless ( otherwise as Dan 
pointed out, the hw_rf_enabled flag would prevent this ).

One caveat...it appeared to me as if the NM code in 0.6.6 was 
interpreting the GetPower return values incorrectly( ie. it looked like 
interpreted TRUE as killswitch ON, as opposed to power ON ).  I had to 
reverse the value returned by my KillSwitch::GetPower method, otherwise 
NM disabled wireless on startup.

I additionally implemented a power-saving feature using some of the same 
logic.  I modified the scanning code so that when the scan_interval gets 
bumped to  INACTIVE ( ~2min ), I disable the interface at the beginning 
of the interval and then wake it up right before the next scheduled scan.

Note - the one caveat is that my Hal KillSwitch method utilizes a 
private DeepSleep ioctl, so the card isn't totally powered off, but is 
close enough to show some substantial power-savings.

I plan on publishing my work via my launchpad PPA ( personal package 
archive ), and will drop a note to the list when the code's available ( 
hopefully tomorrow ).

Regards,
Tony Espy
Canonical