Line6 USB driver in ALSA?

Line6 USB driver in ALSA?

[Markus Grabner]

	Hi everybody!

    I just had a brief conversation with Lee Revell about the question if a 
USB driver for Line6 guitar equipment I am working on since 2004 (see 
http://www.tanzband-scream.at/line6) could be included in ALSA. In 
particular, the following devices are supported:
*) POD series (http://www.line6.com/products/pods): these devices digitally 
simulate the sound of different guitar amplifiers. The user can control these 
devices by several dials without connecting them to the PC, or by appropriate 
software running on a PC to which the device is connected via USB. Moreover, 
the guitar signal can be captured, and simultaneously a PCM signal from the 
PC can be played back (full-duplex).
*) Variax guitars (http://www.line6.com/variax) connected to the PC via an USB 
interface (http://www.line6.com/variaxWorkbench): these guitars digitally 
simulate the sound of different guitars. The model parameters (e.g., pickup 
type and position) can be modified via USB (the current version of the Linux 
driver can only read these parameters, however).

The driver I wrote registers the POD devices as a soundcard, therefore the PCM 
portion would perfectly fit into ALSA. Moreover, POD parameters are 
controlled via ALSA's MIDI interface, commands are translated to USB (the 
devices also have a MIDI port, which can be accessed with the standard raw 
MIDI driver, but PCM is not available via MIDI).
However, I'm not so sure if other features of the driver are within the scope 
of ALSA. These include
*) a set of files registered under /sys/bus/usb/drivers/... to allow access to 
the current states of the POD/Variax model parameters (as ASCII numbers)
*) a method to access all parameters of a single or multiple models as a 
binary block of data
*) a guitar tuner
*) and some more features not immediately related to audio

The current driver source code is available under 
"http://www.tanzband-scream.at/line6/download/line6usb-0.6.1.tar.bz2". The 
main files are:
*) pcm.*: the PCM interface
*) midi.*: the MIDI interface
*) pod.*: POD-specific code
*) variax.*: Variax-specific code
*) driver.*: generic code for all supported Line6 devices

What is your opinion on how such a driver could fit into the ALSA concept?

	Kind regards,
		Markus


-- 
Markus Grabner - Computer Graphics and Vision
Graz University of Technology, Inffeldgasse 16/II, 8010 Graz, Austria
Phone: +43/316/873-5041, Fax: +43/316/873-5050
WWW: http://www.icg.tu-graz.ac.at/Members/grabner


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Re: Line6 USB driver in ALSA?

[Lee Revell]

On Sun, 2006-02-26 at 12:07 +0100, Markus Grabner wrote:
> 	Hi everybody!

Why don't you just submit your driver in its current form as a patch
against ALSA CVS, and we can go from there?  I'm a big fan of "release
early, release often".  If it's not too much work, you can break out the
parts that don't fit into the ALSA sources and submit those to LKML
separately.

Lee



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Re: Line6 USB driver in ALSA?

[Clemens Ladisch]

Markus Grabner wrote:
> The driver I wrote registers the POD devices as a soundcard, therefore the PCM 
> portion would perfectly fit into ALSA. Moreover, POD parameters are 
> controlled via ALSA's MIDI interface, commands are translated to USB (the 
> devices also have a MIDI port, which can be accessed with the standard raw 
> MIDI driver, but PCM is not available via MIDI).
> However, I'm not so sure if other features of the driver are within the scope 
> of ALSA. These include
> *) a set of files registered under /sys/bus/usb/drivers/... to allow access to 
> the current states of the POD/Variax model parameters (as ASCII numbers)

AFAICS those parameters could be handled by a userspace application that
handles some MIDI messages.

> *) a method to access all parameters of a single or multiple models as a 
> binary block of data

ditto

> *) a guitar tuner

How does its interface look like?

> *) and some more features not immediately related to audio

It might make sense to put them into the same driver if they're handled
through the same USB interface.


Regards,
Clemens


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