Configuring PulseAudio to use ALSA PCM plugin

[bchang_2@xxxxxxxxx (Ben C)]

Hello, I'm trying to configure PulseAudio to use an ALSA PCM plugin in the audio 
chain.

PulseAudio as been configured with:
load-module module-alsa-sink device=my_sink

And ALSA has been configured with:

pcm.my_sink {
    type my_pcm_plugin
    slave.pcm "hw:0,0"
}

However, my_sink seems to get hogged, and be considered "busy". I had to 
configure dmix in order for this setup to work. Is that normal? Am I configuring 
something incorrectly? I would assume that to PulseAudio, these ALSA output 
devices are the same, whether it's a physical device or a virtual one. But when 
using the default configuration (and my_pcm_plugin is not in the chain), dmix 
isn't necessary.

Thanks for your help.