On Wed, 25 Feb 2004, Gupta, Kshitij wrote:
> hi, > I have a very trivial question about the dma transfers with respect > to ALSA framework. > > Let me first explain a scenario > We have a Circularly linked Buffer pool > > buf1 buf2 buf3 buf4 .... bufn > > In very simple terms playing an audio stream is reading from these buffers > and continuously dma'ing it to the audio device (let's assume we have a read > and write register with the audio device). And in this circulary linked > audio buffer the user fills the data and the driver empties it to the > device. > > Now I am not able to fit this scenario in the ALSA framework. I am > referrring to alsa-kernel/arm/sa11xx-uda1341.c file as a reference for my > driver. And here I don't understand where do we specify the the exact dma > parameters (like the start address of buffer and the destination address). You should do most of the hw setup in the .hw_params callback. You get pointers to the substream and hw_params structures and you have to setup the hw and the buffer as requested. These macros may be useful params_period_bytes(), params_buffer_bytes(), snd_pcm_substream_sgbuf(), snd_sgbuf_get_addr(). There are many others, look at the sources :) -- Giuliano. ------------------------------------------------------- SF.Net is sponsored by: Speed Start Your Linux Apps Now. Build and deploy apps & Web services for Linux with a free DVD software kit from IBM. Click Now! http://ads.osdn.com/?ad_id=1356&alloc_id=3438&op=click _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
