[alsa-devel] Query regarding pointer callback

[Pharaoh .]

Hi

In Writing an ALSA driver, it is said that
pointer callback is called usually from the buffer-update routine in
the pcm middle layer, which is invoked when snd_pcm_period_elapsed()
is called in the interrupt routine. Then the pcm middle layer updates
the position and calculates the available space, and wakes up the
sleeping poll threads, etc

What are the other places from where pointer callback is called? If it
is not called from any other routine then does it mean that interrupts
are occuring?