[alsa-devel] [PATCH v4 4/7] soundwire: Handle multiple master instances in a stream

[Shreyas NC]

On Mon, Jul 02, 2018 at 03:22:07PM -0500, Pierre-Louis Bossart wrote:
> 
> >  /**
> >@@ -918,13 +951,22 @@ static void sdw_release_master_stream(struct sdw_stream_runtime *stream)
> >  int sdw_stream_remove_master(struct sdw_bus *bus,
> >  		struct sdw_stream_runtime *stream)
> >  {
> >+	struct sdw_master_runtime *m_rt, *_m_rt;
> >+
> >  	mutex_lock(&bus->bus_lock);
> >-	sdw_release_master_stream(stream);
> >-	sdw_master_port_release(bus, stream->m_rt);
> >-	stream->state = SDW_STREAM_RELEASED;
> >-	kfree(stream->m_rt);
> >-	stream->m_rt = NULL;
> >+	list_for_each_entry_safe(m_rt, _m_rt,
> >+			&stream->master_list, stream_node) {
> >+
> >+		if (m_rt->bus != bus)
> >+			continue;
> >+
> >+		sdw_master_port_release(bus, m_rt);
> >+		sdw_release_master_stream(m_rt, stream);
> >+	}
> >+
> >+	if (list_empty(&stream->master_list))
> >+		stream->state = SDW_STREAM_RELEASED;
> When a master is removed, there is an explicit test to make sure the stream
> state changes when there are no masters left in the list, but...
>
> >  	mutex_unlock(&bus->bus_lock);
> >@@ -1127,7 +1169,7 @@ int sdw_stream_add_master(struct sdw_bus *bus,
> >  	stream->state = SDW_STREAM_CONFIGURED;
> ... it's not symmetrical for the add_master case. The stream state changes
> on the first added master. In addition the stream state changes both when a
> slave is added and a master is added.
> Is this intentional or not - and are there side effects resulting from this
> inconsistency?
>

For remove_master, we already know the number of Masters in the stream and
hence we change the state to RELEASED only when there are no Masters
left in stream.

But, in the add_master case, we have no idea on how many master instances
are part of the stream and hence how many times add_master would be called.
So, we change the stream state to CONFIGURED when the first Master is added.
I can add a comment if that helps :)

Yes, it is added intentionally (or rather because we could not think of any
other suitable way) and we dont see any side effects. Anything
that you could think of?

IIRC, we had this discussion when the stream series was posted. But I am
unable to find those mails :(

Thanks for the review!

--Shreyas
--