[alsa-devel] how to update hw_ptr and appl_ptr

Clemens Ladisch clemens at ladisch.de
Tue Jun 26 14:27:04 CEST 2012

Zhen Fu wrote:
> when DMA handler called snd_pcm_period_elapsed, so I want to know how
> about update hw_ptr in ALSA.

snd_pcm_period_elapsed() calls snd_pcm_update_hw_ptr0(), which calls
your driver's .pointer callback.  The value returned by that callback
essentially is the hw_ptr (although it doesn't wrap around at the end
of the buffer).

Why do you care about hw_ptr?


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