[RFT] ALSA control service programs for Fireworks board module

[Takashi Sakamoto]

Hi,

This is request-for-test (RFT) to the ALSA control service programs for
devices with Fireworks board module. The program is available in
'topic/service-for-efw' of below repository, and the RFT is corresponding
to Pull Request #2:

* https://github.com/alsa-project/snd-firewire-ctl-services/

If you have listed devices and handle them by ALSA fireworks driver, please
test the service program according to the below instruction.

  * Mackie (Loud) Onyx 1200F
  * Mackie (Loud) Onyx 400F
  * Echo Audio Audiofire 12 (till Jul 2009)
  * Echo Audio Audiofire 8 (till Jul 2009)
  * Echo Audio Audiofire 12 (since Jul 2009)
  * Echo Audio Audiofire 8 (since Jul 2009)
  * Echo Audio Audiofire 2
  * Echo Audio Audiofire 4
  * Echo Audio Audiofire Pre8
  * Gibson Robot Interface Pack (RIP) for Robot Guitar series

Background
----------

The models with Fireworks board module are already supported by ALSA
fireworks driver for their isochronous packet stream functionality
and vendor-specific transaction. Although the driver allows userspace
applications to process PCM frames and MIDI messages in the packet
streaming, it doesn't support the other functionalities such as volume
control since it can be achieved by any usespace application which
executes ioctl(2) to ALSA hwdep character device for the transaction.

The service program is to satisfy the demand to control the models.
ALSA control applications can request the control by IPC to the service
program.

In detail of mechanism, please read README.rst in the repository[1].
You can see some illustrations.

How to build
-------------

The project depends on several libraries in below repositories:

* glib[2]
* alsa-gobject v0.1.0[3]
* libhinawa v2.0.0[4]

Before building it, please install them with gobject-introspection support.

The project is written by Rust programming language[5] and packaged by
cargo[6]. To build, just run below commands in the environment to connect
to internet:

```
$ git clone https://github.com/alsa-project/snd-firewire-ctl-services.git -b topic/service-for-efw
$ cd snd-firewire-ctl-services
$ cargo build
```

All of required crates are downloaded automatically, then start build.

Executables
-----------

After building, `snd-fireworks-ctl-service` executable is available.

When running, the program adds and maintains control elements, then enter
event loop to dispatch events. The added elements are visible and manipulable
for any userspace applications. The program dispatch any manipulation
event for transactions to control actual device.

The executable has an option for the numerical ID of sound card.

```
Usage:
  snd-fireworks-ctl-service CARD_ID

  where:
    CARD_ID: The numerical ID of sound card.
```

It's easy to run the executable by cargo, like:

```
$ cargo run --bin snd-fireworks-ctl-service 2
```

Receiving SIGTERM signal terminates the event loop, then the program
finishes.

During runtime, any ALSA control applications can enumerate and manipulate
the added control elements. This is an example of Echo Audio AudioFire 2:

```
$ amixer -c 2 controls
numid=33,iface=MIXER,name='clock-detect'
numid=2,iface=MIXER,name='clock-rate'
numid=1,iface=MIXER,name='clock-source'
numid=36,iface=MIXER,name='input-meter'
numid=34,iface=MIXER,name='midi-in-detect'
numid=35,iface=MIXER,name='midi-out-detect'
numid=6,iface=MIXER,name='monitor-gain'
numid=7,iface=MIXER,name='monitor-gain',index=1
numid=8,iface=MIXER,name='monitor-gain',index=2
numid=9,iface=MIXER,name='monitor-gain',index=3
numid=10,iface=MIXER,name='monitor-gain',index=4
numid=11,iface=MIXER,name='monitor-gain',index=5
numid=12,iface=MIXER,name='monitor-mute'
numid=13,iface=MIXER,name='monitor-mute',index=1
numid=14,iface=MIXER,name='monitor-mute',index=2
numid=15,iface=MIXER,name='monitor-mute',index=3
numid=16,iface=MIXER,name='monitor-mute',index=4
numid=17,iface=MIXER,name='monitor-mute',index=5
numid=24,iface=MIXER,name='monitor-pan'
numid=25,iface=MIXER,name='monitor-pan',index=1
numid=26,iface=MIXER,name='monitor-pan',index=2
numid=27,iface=MIXER,name='monitor-pan',index=3
numid=28,iface=MIXER,name='monitor-pan',index=4
numid=29,iface=MIXER,name='monitor-pan',index=5
numid=18,iface=MIXER,name='monitor-solo'
numid=19,iface=MIXER,name='monitor-solo',index=1
numid=20,iface=MIXER,name='monitor-solo',index=2
numid=21,iface=MIXER,name='monitor-solo',index=3
numid=22,iface=MIXER,name='monitor-solo',index=4
numid=23,iface=MIXER,name='monitor-solo',index=5
numid=38,iface=MIXER,name='monitoring'
numid=37,iface=MIXER,name='output-meter'
numid=31,iface=MIXER,name='output-mute'
numid=30,iface=MIXER,name='output-volume'
numid=4,iface=MIXER,name='playback-mute'
numid=5,iface=MIXER,name='playback-solo'
numid=3,iface=MIXER,name='playback-volume'
numid=32,iface=MIXER,name='stream-playback-routing'
```

Access permissions for relevant character devices
--------------------------------------------------

The executable manipulates below character devices to dispatch, and emit
events from end to end. The '%u' is the numerical number of instance in
each subsystem:

 * ALSA control character device (/dev/snd/controlC%u)
 * ALSA hwdep character device (/dev/snd/hwC%uD%u)
 * Linux firewire character device (/dev/fw%u)

Feedback
--------

Any feedback is welcome. For questions, please use mailing list of alsa-devel
or alsa-users[7]. For issues, please use service of github.com[8].

Issues
------

The name of control elements are not fixed yet since the convention of
name for element set is not clear yet for recording equipment.

Users may feel inconvenience to which channel corresponds to which physical
port. Furthermore, in the case that element set includes several elements,
it's unclear that which element corresponds to which physical port as well.
ALSA control core has no feature for the above issues at present.

[1] https://github.com/alsa-project/snd-firewire-ctl-services
[2] https://gitlab.gnome.org/GNOME/glib
[3] https://github.com/alsa-project/alsa-gobject/
[4] https://github.com/alsa-project/libhinawa
[5] https://www.rust-lang.org/
[6] https://doc.rust-lang.org/cargo/
[7] https://www.alsa-project.org/wiki/Mailing-lists
[8] https://github.com/alsa-project/snd-firewire-ctl-services/issues


Regards

Takashi Sakamoto