[alsa-devel] Newbie needs help to understand SNDRV_PCM_TRIGGER_START?

I am writing my first ALSA driver. We have hardware where the amp is controlled with another CPU (non Linux) so I have to forward the buffers from ALSA to it. We do not have working solution on another CPU so I cannot test sound playback yet. ALSA hits trigger method in my driver and soon after it leaves my trigger method throws an null pointer exception (probably since I did not do anything in my trigger method). I am wondering if the ALSA will call SNDRV_PCM_TRIGGER_START every single time new buffer is available. Do I need to manage circular queue of buffers or ALSA is doing this for me already? Thanx