[gnome-bluetooth] No Bluetooth Found, Plug in a dongle to use Bluetooth

[Bjørn Forsman]

On 19 July 2016 at 13:30, Bjørn Forsman <bjorn.forsman at gmail.com> wrote:
> I'm trying to get gnome-bluetooth working on NixOS, but I'm facing a
> blocking issue.
> [...]
>
> The problem:
>
> The "gnome-control-center bluetooth" GUI says "No Bluetooth Found" and
> "Plug in a dongle to use Bluetooth", even though I have a working
> bluetooth dongle[1].
>
> Turning on verbose output, I see this:
>
> $ gnome-control-center -v bluetooth
> ** (gnome-control-center:15062): DEBUG: Enabling debugging
> ** (gnome-control-center:15062): DEBUG: No extra argument
> (gnome-control-center:15062): Bluetooth-DEBUG: Default adapter changed
> to: (none)
> (gnome-control-center:15062): bluetooth-cc-panel-DEBUG: Updating
> airplane mode: BluetoothHasAirplaneMode 0,
> BluetoothHardwareAirplaneMode 0, BluetoothAirplaneMode 0, AirplaneMode
> 0
> (gnome-control-center:15062): bluetooth-cc-panel-DEBUG: No Bluetooth available

I had another look and found the source of the problem.

/dev/rfkill was lacking write permissions.

Basically this happens:

1. gnome-settings-daemon complains at startup: "Could not open RFKILL
control device, please verify your installation". (I didn't notice
before, the log is full of warnings...)

2. "gnome-control-center bluetooth" asks gnome-settings-daemon (over
D-Bus) for "BluetoothHasAirplaneMode". Because the
gnome-settings-daemon couldn't open /dev/rfkill in RW mode it says
"no" (0).

3. "gnome-control-center bluetooth" concludes that there are no
bluetooth dongles, because of that BluetoothHasAirplaneMode == 0
thing. See source code at
https://git.gnome.org/browse/gnome-control-center/tree/panels/bluetooth/cc-bluetooth-panel.c#n145.

My first impression is that step 3 is a bug, because I can use
"bluetoothctl" to connect/pair bluetooth devices just fine without
write permissions to /dev/rfkill. So why should not the GUI work?

Best regards,
Bjørn Forsman