[alsa-devel] Echo Fireworks control protocol (was Re: Sample program for hwdep interface)

[Takashi Sakamoto]

> Sure, definitely; my point was that the kernel ABI which userspace mixer
> applications are going to use could be
>    a) the ALSA hwdep interface, or
>    b) the ALSA hwdep interface together with firewire-core's firewire-cdev
>       interface,
> but I understood that b) is the first choice.  Specifically, provide in
> ALSA hwdep only the absolutely necessary interfaces and do as much as
> possible via firewire-cdev.

Exactly.

> and because some devices (which ones?) may have write-only registers,
> of which both streaming driver and mixer application want to know
> what is being written there.

For this purpose, ALSA Control interface can also be used. One example 
is M-Audio 'Firewire 1814', see:
[PATCH 52/52] bebob: Add support for M-Audio special Firewire series
http://mailman.alsa-project.org/pipermail/alsa-devel/2014-January/071873.html

And See:
[alsa-devel] include/uapi/firewire.h for other firewire drivers
http://mailman.alsa-project.org/pipermail/alsa-devel/2013-November/068069.html

(This device has another bit issue but here I don't mention about it.)

> Furthermore, it can't be a kernel interface like sysfs or configfs
> because of the complexity and variety of control protocols of FireWire
> audio devices.

Indeed.


Takashi Sakamoto
o-takashi at sakamocchi.jp