[proaudio] Proposed libffado updates

[Karl Lindén <karl.j.linden@xxxxxxxxx>]

Hi list!

As you might have noted I have carried out an update for the libffado
ebuilds lately. Please, ffado users, test this one if you have the
possibility.

I am planning more updates to the libffado ebuilds. Since I do not own
any firewire hardware (I merely update the ebuilds to get on with the
jack-audio-connection-kit multilib effort) I would really like to
receive some feedback and testing help from people using the ffado
drivers before updating any ebuilds.

The first update I would like to apply is just a small one. Add an
expat USE flag, so that expat can be used instead of libxmlpp. This is
supported directly by the build system so it is very trivial to
implement.

The second enhancment is much bigger. The libffado build system
includes possibilities to choose exactly which drivers to build,
instead of building the default. Furthermore the default set of
drivers does not cover all available drivers, so some drivers are only
available through direct choice. This can easily be controlled through
the USE_EXPAND functionality. For example a FFADO_CARDS variable could
be used (compare INPUT_DEVICES or VIDEO_CARDS). It should not be very
hard to implement and I believe it would be beneficial since it gives
more possibility to chose, customize and make the package more
slimmed.

The third and most important change is the multilib migration which I
think can be performed soon, since all necessary dependencies are
converted (except libxmlpp, but it can be circumvented using expat). I
no longer think dbus-c++, since it is only used to build binaries.

Please let me know if you find these proposed changes interesting. I
am also grateful for any other feedback on this topic. I can implement
the features, but I still need someone that can test the changes and
make sure everything works OK.

Regards,
Karl