[alsa-devel] HDA driver without interrupt

[Clemens Ladisch]

Fanchao Liu wrote:
> It can transfer data via DMA,the problem is I don't know when to
> update hw_ptr and other pointers without interrupt.

Does the hardware have some other means to at least read the current
position?

> I set a timer and call snd_pcm_period_elapsed() every 50ms but get
> underrun error.

With a call to snd_pcm_period_elapsed(), the driver guarantees that the
current position is at or after the next period boundary.


Regards,
Clemens