Comment # 3 on bug 1219803 from Takashi Iwai

Thanks.  The problem is that this device has only two DACs while there are
three outputs (speaker, bass speaker and headphone).  So the driver tried to
assign front and bass, while sharing the same DAC between the bass and the
headphone.
Admittedly, this doesn't look ideal assignment.

We may assign one volume for both speaker and bass speaker (those are tied),
and another for the headphone, too.  It's a question of trade-off.

I'll check a bit more deeply later.