DSP under ALSA

[kawshol]

Hi,
I wish to support dedicated DSP under ALSA, My DSP has a small OS and
can support encoder and decoders running on them. What I fail to
understand is it has Control, PCM, Mixer and Sequencer interfaces if I
need to pass the raw stream of MP3 or some other encoded raw sound
streams to DSP. How do I pass this stream using ALSA? Once I pass this
to DSP can I mix the input and control that using the mixer interface?

I think that the PCM interface is to pass the PCM data. If my decoderis
on the DSP why should I get the data back and pass again forrendering?

Best Regards,