Re: full/half duplex support

[Takashi Iwai <tiwai@suse.de>]

At Mon, 15 Nov 2004 17:03:21 +0100,
Luuk van Dijk wrote:
> 
> LS. 
> 
> I am currently writing a driver for the ADI 1836 on the (ongoing) 
> blackfin/uclinux port (blackfin.uclinux.org) and I have some questions (that 
> I'll post in separate mails, so that they may be separate threads) 
> 
> The particular hardware configuration I am programming for is full-duplex in 
> principle, i.e. it should be no problem to send and receive pcm bitstreams 
> simultaneously, except that it requires that both dma channels are started 
> simultaneously.  Currently, I configure an unused substream with a dummy dma 
> buffer, but the alsa mid layer seems to handle this badly: it appears to 
> re-triggers the last-started substream when it finds out that the dma is at 
> an other address than it expects. 

Sorry, the situation is not clear for me.
Do you mean substream as the ALSA term?

So, you have two or more substreams assigned to a single PCM device,
and the DMAs are free-running when the substreams are unused?


Takashi


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