[pulseaudio-discuss] [PATCH v3 1/2] refactor default sink/source handling

[Georg Chini]

On 16.02.2017 11:09, Tanu Kaskinen wrote:

"Refactor" is the wrong word, you are changing the logic.
Maybe redesign is a better verb.

> Currently the default sink policy is simple: either the user has
> configured it explicitly, in which case we always use that as the
> default, or we pick the sink with the highest priority. The sink
> priorities are currently static, so there's no need to worry about
> updating the default sink when sink priorities change.
>
> I intend to make things a bit more complex: if the active port of a sink
> is unavailable, the sink should not be the default sink, and I also want
> to make sink priorities dependent on the active port, so changing the
> port should cause re-evaluation of which sink to choose as the default.
> Currently the default sink choice is done only when someone calls
> pa_namereg_get_default_sink(), and change notifications are only sent
> when a sink is created or destroyed. That makes it hard to add new rules
> to the default sink selection policy.
>
> This patch moves the default sink selection to
> pa_core_update_default_sink(), which is called whenever something
> happens that can affect the default sink choice. That function needs to
> know the previous choice in order to send change notifications as
> appropriate, but previously pa_core.default_sink was only set when the
> user had configured it explicitly. Now pa_core.default_sink is always
> set (unless there are no sinks at all), so pa_core_update_default_sink()
> can use that to get the previous choice. The user configuration is saved
> in a new variable, pa_core.configured_default_sink.
>
> pa_namereg_get_default_sink() is now unnecessary, because
> pa_core.default_sink can be used directly to get the
> currently-considered-best sink. pa_namereg_set_default_sink() is
> replaced by pa_core_set_configured_default_sink().

It seems a bit strange to me, that module-default-device-restore and
module-switch-on-connect set the configured_default_* variables, because
these should be the user configured values.
If a user has configured his default sink/source, 
module-switch-on-connect will change
it if some new device (for example a bluetooth headset) turns up. This 
is then saved
as the new default sink/source, so the original user setting is lost and 
on the next start
of pulseaudio, it will use the (possibly not existent) device as the 
default.
It also means, that if there is no user configured value, it suddenly 
will be there
because module-default-device-restore saves the current default as the 
user default.

I would use two variables, user_configured_default_* and 
system_configured_default_*
and let module-default-device-restore save both values. When loading the 
configuration,
the module can check if the system configured default still exists and 
else revert to
the user setting. Module-switch-on-connect would use the system_ variables.
The system_configured_default_* variables would take the role of the current
configured_default_* variables and the user_configured_default_* 
variables would
only get copied into them if the sink/source is valid.

This would also mean, that the user can configure any value for the 
default, if the
sink or source does not exist, it won't be used. The user configured 
value will
also survive any temporary changes done by module-switch-on-connect.

>   
> +void pa_core_set_configured_default_sink(pa_core *core, pa_sink *sink) {
> +    pa_sink *old_sink;
> +
> +    pa_assert(core);
> +
> +    old_sink = core->configured_default_sink;

Why do you use a new variable here? If you move the assignment after
the pa_log_info() the variable is not necessary. This also applies to a few
other functions.

> +
> +    if (sink == old_sink)
> +        return;
> +
> +    core->configured_default_sink = sink;
> +    pa_log_info("configured_default_sink: %s -> %s",
> +                old_sink ? old_sink->name : "(unset)", sink ? sink->name : "(unset)");
> +
> +    pa_core_update_default_sink(core);
> +}