On Tue, 2006-08-01 at 20:48 +0100, Julien Bramary wrote:
> I'm an Alsa beginner and I'm trying to write an alsa driver for an embedded dac on ARM.
>
> >From Iwai's doc:
>
> /* trigger callback */
> static int snd_mychip_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
> {
> switch (cmd) {
> case SNDRV_PCM_TRIGGER_START:
> // do something to start the PCM engine
> break;
> case SNDRV_PCM_TRIGGER_STOP:
> // do something to stop the PCM engine
> break;
> default:
> return -EINVAL;
> }
> }
>
> My question here is,
> What are we supposed to do to start the PCM engine?
> Because, I'm currently doing nothing, and yet it starts anyway...
> I'd like to understand to have more control.
"PCM engine" refers to the hardware's PCM engine, not ALSA's. It's 100%
device dependent - you need to consult the docs for your sound device to
determine how to start the PCM.
Lee
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