Re: Driver(s) for IEEE 1394 based break out boxes

[Takashi Iwai <tiwai@suse.de>]

At Mon, 12 Jul 2004 21:19:30 +0200,
Daniel Wagner wrote:
> 
> On the on hand, there exists already the IEEE 1394 stack with IEC
> 61883 support in user-land.  I don't know if the libiec61883 is already
> ready to use but still it exists.  As I understand the general idea
> behind libraw1394 and libiec61883 is to do as much as possible in
> users-pace.  Any application which wants to take advantage of IEEE 1394
> based sound cards has to use those libraries.  I guess it means for
> jack to have a new backend in order to use those cards.  But most
> application wont be aware of this interface, I suppose.

IIRC, JACK has already a driver for IEC61883.
Don't know whether it really works, though.

> On the other hand ALSA provides a well known interface which most
> sound based application are using.  To write a new driver for a sound
> card, you end up writing an ALSA kernel driver because libasound is
> not designed to use other interfaces than the ALSA kernel interface
> (this is an assumption).  So it is not possible to use libraw1394 and
> libiec61883.  A new kernel driver has to be written with implements
> those parts.  Of course it needs some more things but I'm just writing
> my lousy ordered thoughts down.
> 
> The question is which way to go?  Get the break out boxes working with
> the existing libraries or write an ALSA driver which implements those
> parts again?  Personaly, I think ALSA might be the better idea but it
> does not make use of the already written code.  Maybe there exists a
> better way...

The user-space driver can be implemented on alsa-lib as a plugin.
For example, you can find ALSA <-> JACK transparent layer.

I once thought of that for usb driver, but it wasn't possible because
usbfs can't work with isochronous transfer.

If libiec61883 provides for stream reading/writing, it wouldn't be too
hard to implement.


IMO, the implementation of the kernel driver is the last resort.
It might be easier as a result, but we can try at first the user-space
implementation...


Takashi


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