Bug#805414: gdm3: disable pulseaudio to prevent capturing A2DP sink on session start

[Jude DaShiell]

What happens to someone who only has a bluetooth keyboard and has a 
bluetooth dongle connected to their computer to use bluetooth 
temporarily since their usb keyboard broke?

On Mon, 3 Jul 2017, Felipe Sateler wrote:

> Date: Mon, 3 Jul 2017 10:27:36
> From: Felipe Sateler <fsateler at debian.org>
> To: Antoine Beaupr? <anarcat at debian.org>,
>     debian-accessibility at lists.debian.org
> Cc: Michael Biebl <biebl at debian.org>, 805414 at bugs.debian.org,
>     Aurelien Jacobs <aurel at gnuage.org>
> Subject: Re: Bug#805414: gdm3: disable pulseaudio to prevent capturing A2DP
>     sink on session start
> Resent-Date: Mon,  3 Jul 2017 14:28:34 +0000 (UTC)
> Resent-From: debian-accessibility at lists.debian.org
> 
> Adding the a11y list to CC.
>
> Dear a11y team, a short summary for you: Currently, pulseaudio does not
> negotiate bluetooth devices the same way it does with alsa devices, with a
> result that is undesirable: if the gdm login screen grabs the BT device, it
> becomes unavailable in the logged in session. The change being discussed
> here is to disable bluetooth in the gdm login screen.
>
> On Mon, Jul 3, 2017 at 10:20 AM, Antoine Beaupr? <anarcat at debian.org> wrote:
>
>> On 2017-07-03 15:46:20, Michael Biebl wrote:
>>> Am 03.07.2017 um 00:05 schrieb Antoine Beaupr?:
>>>> On 2017-07-02 23:43:55, Michael Biebl wrote:
>>>>> Am 02.07.2017 um 23:36 schrieb Antoine Beaupr?:
>>>>>> On 2017-07-02 23:16:19, Michael Biebl wrote:
>>>>>
>>>>>>> Have you tested the workaround from the arch wiki and can you
>> confirm it
>>>>>>> works?
>>>>>>
>>>>>> I cannot, unfortunately, test this anymore, as I have disabled the
>>>>>> pulseaudio socket as directed earlier, with:
>>>>>>
>>>>>> rm /var/lib/gdm3/.config/systemd/user/sockets.target.wants/
>> pulseaudio.socket
>>>>>>
>>>>>> I don't know what that was pointing to, so I can't quite restore that
>>>>>> behavior directly.
>>>>>
>>>>> That's from the postinst:
>>>>>
>>>>> UNIT=/usr/lib/systemd/user/pulseaudio.socket
>>>>> USERUNITDIR=/var/lib/gdm3/.config/systemd/user
>>>>> if ! [ -L $USERUNITDIR/sockets.target.wants/pulseaudio.socket ]; then
>>>>>   mkdir -p $USERUNITDIR/sockets.target.wants
>>>>>   ln -sf $UNIT $USERUNITDIR/sockets.target.wants
>>>>> fi
>>>>>
>>>>> You can run that manually or simply re-install the gdm3 package so that
>>>>> code is run again.
>>>>
>>>> Thanks! I believe I have rolled back the workarounds and implemented the
>>>> fix default.pa documented in the Arch wiki. Everything seems to work
>>>> normally now, ie. I can correctly connect through A2DP to my bluetooth
>>>> speaker.
>>>
>>> Since concerns were raised that this might break existing a11y setups, I
>>> don't plan to make an upload with this change.
>>
>> I don't understand the impact this could have regarding
>> accessibility. There are, as far as I know, currently no usable way to
>> have bluetooth audio working at all in the gdm3 login prompt, because
>> there's no way to associate a device, so there's no loss of
>> functionality here. But there *is* a loss of functionality for
>> everyone (*including* screen reader users) *after* the user is logged
>> in: they cannot correctly configure bluetooth devices!
>>
>
> Bluetooth pairings are global. Once you configured them in your user
> session, they will become available to gdm too.
>
>
>>
>> Can we get a better idea of the use case you are worried about here?
>>
>
> Here is where the input of the a11y team would be very appreciated. Is
> disabling bluetooth in the login screen likely to cause problem?
>
>
>>
>> To be really clear here, the change I am proposing is the one documented
>> in the Arch wiki and now also in the Debian wiki:
>>
>> https://wiki.debian.org/BluetoothUser/a2dp#Workaround_
>> 2:_disable_pulseaudio.27s_bluetooth_in_gdm
>>
>> which currently consists of adding the following
>> /var/lib/gdm3/.config/pulse/default.pa file:
>>
>> #!/usr/bin/pulseaudio -nF
>> #
>>
>> # load system wide configuration
>> .include /etc/pulse/default.pa
>>
>> ### unload driver modules for Bluetooth hardware
>> .ifexists module-bluetooth-policy.so
>>   unload-module module-bluetooth-policy
>> .endif
>>
>> .ifexists module-bluetooth-discover.so
>>   unload-module module-bluetooth-discover
>> .endif
>>
>> How would this break accessibility?
>>
>
> My own thought is that if your only speakers are BT, how are you going to
> have the screen read if there is no BT?
>
>

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