Re: [Xenomai-help] RTDM/ALSA hybrid driver ?

[Jan Kiszka <jan.kiszka@domain.hid>]

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Thomas Witzel wrote:
> Hello,
> 
> I'm now trying to create a sound driver that will start and stop playback in 
> real time. Is it better to implement a driver for RTDM from scratch, or is it 
> reasonable to just add a RTDM interface for the required functionality to an 
> existing ALSA driver ? The advantage of the latter approach is of course, 
> that everything that doesn't need to be done in realtime already exists 
> through ALSA and I only would have to implement the pcm triggers through 
> RTDM. Is that reasonable at all ?

Yes, this can be reasonable. You will fork the driver effectively, but
you should be able to reuse init/cleanup parts for this. Basically, this
is how most RTnet drivers were developed.

But how hard and how tight are your RT requirements? I'm asking because
I know that a lot of people are using unmodified ALSA drivers over the
PREEMPT_RT kernel for real-time recording, processing, and playback.
Maybe this can already provide you what you need. But I don't know the
internal design of ALSA, if there are any pitfalls hidden like dynamic
buffer management.

Jan


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