What is the format of dma_area?

[Bill Gatliff <bgat@billgatliff.com>]

Guys:


I'm trying to write a PCM driver that uses an AC97 codec, on an ARM 
host, but no DMA.  (Please pardon some of my terminology, I'm a bit of 
an ALSA noob).

My trigger() looks something like this:

int *buffer;
int bytes;
...
  switch (cmd) {
  case SNDRV_PCM_TRIGGER_START:
    bytes = frames_to_bytes(substream->runtime, 
substream->runtime->period_size);
    buffer = substream->runtime->dma_area;
...

Then, I copy *buffer++ out to the codec one 32-bit chunk (truncated to 
20 bits) at a time.

One thing I don't understand is how dma_area is formatted.  Is it a 
stream of integers, like this?

int dma_area[channels][samples];

... or like this?

int dma_area[samples][channels];

... or what?  I'm having trouble figuring out where the left- and 
right-channel data is in the dma buffer.


Thanks!


b.g.

-- 
Bill Gatliff
bgat@billgatliff.com



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